Rozprawy doktorskie na temat „Neuromuscular performance”

Women athletes are more likely to tear their anterior cruciate ligament than their male counterparts. The female athlete has a complex system of steroid hormones that are continually changing. These sex hormones that fluctuate throughout each month may influence knee injuries, specifically the anterior cruciate ligament. The increased incidence in women is thought to be multifactorial, a combination of structural, anatomical, or biomechanical factors. The NCAA has reported that 75 percent of anterior cruciate ligament injuries are non-contact in competitive jumping or pivoting sports. In this study, the effects of the menstrual cycle on neuromuscular performance were investigated. Fifteen healthy females with regular menstrual cycles completed the various tests of this study for three phases of the menstrual cycle. All females were categorized as moderate or vigorous exercisers from an activity questionnaire. This study used a repeated measures experimental design; therefore, each participant served as her own control. The participants completed a series of two tests, including functional balance and fatigability. Each series was completed during three different phases of the menstrual cycle: menstruation, follicular and luteal. The participants used ovulation kits to predict the luteal phase. These phases were then verified through blood tests at each exercise session. The reaction time and balance test was performed with a BOSU wobble board placed on a force plate. A force platform was utilized to collect center of pressure data from the wobble board. The fatigue test protocol consisted of the participants performing in a pre-fatigue functional test, fatigue protocol and post-fatigue functional ability test. The functional test protocol consisted of two trials of four single-legged hop drills. It was hypothesized that all of the functional tests would have the greatest neuromuscular performance during the follicular phase of the menstrual cycle, and for all of the tests to have differences between the pre- and post-fatigue trials. However, there were no significant differences in the functional tests over the menstrual cycle. There were differences in fatigue in the forward hop and figure eight tests, but the affect of fatigue on performance did not differ across menstrual cycle phases.

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Desportos, Programa de Pós-Graduação em Educação Física, Florianópolis, 2017.
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No ciclismo, a relação hiperbólica entre intensidade de exercício e tempo de exaustão (tlim) apresenta uma potência crítica (PC) e uma quantidade constante de trabalho que pode ser realizado acima da PC (W ). Alguns pressupostos dessa relação ainda não foram completamente testados e/ou confirmados. Dessa forma, os objetivos da presente tese foram: 1) investigar o efeito de duas diferentes taxas de utilização de uma mesma fração da W na magnitude de fadiga neuromuscular (redução do torque muscular pico); 2) investigar o efeito de duas diferentes taxas de utilização de uma mesma fração da W no tlim de um exercício subsequente realizado no domínio severo. A amostra foi composta por 17 sujeitos saudáveis do sexo masculino (25,6 ± 3,7 anos) que participaram voluntariamente. Para atender ao primeiro objetivo, o torque muscular pico dos sujeitos foi determinado por meio de um sprint isocinético all-out (cadência fixa de 120 rpm) em uma condição controle e após dois testes de carga constante programados para depletar 70% W em 3 e 10 min, respectivamente. Em adição, para atender ao segundo objetivo, os sujeitos realizaram dois testes de carga constante programados para depletar 70% W em 3 e 10 min seguidos por um teste até a exaustão na carga correspondente à PC + 10 W. O torque muscular pico nos testes de 3 min (108 ± 19 N.m) e 10 min (112 ± 23 N.m) foi significantemente reduzido (p < 0,05) em comparação à condição controle (135 ± 20 N.m). Contudo, não houve diferença entre as duas condições experimentais (p > 0,05). Por outro lado, o tlim na carga correspondente à PC + 10 W foi mais longo após o teste de 3 min (15,8 ± 6,4 min) que após o teste de 10 min (10,0 ± 6,8 min). Assim, com base nos resultados encontrados, pode ser concluído que a fadiga neuromuscular no domínio severo é independente da taxa de utilização da W quando o trabalho realizado acima da PC é o mesmo. Contudo, o tlim de um exercício severo pode ser prolongado quando é realizado após uma alta taxa de depleção da W . Isso significa que a magnitude da W pode ser aumentada dependendo da amplitude de variação da carga acima da PC.

Abstract : During cycling exercise, power output and time to exhaustion (tlim) describe a hyperbolic relationship, with an asymptote known as critical power (CP) and a fixed amount of work that can be performed above the CP (W ). Some assumptions of this relationship have not yet been fully tested and/or confirmed. Therefore, the aims of this thesis were: to investigate the effect of two different rates of utilization of the same fraction of W on 1) the magnitude of neuromuscular fatigue (reduction of peak muscle torque); and on 2) a tlim performed within the severe-intensity domain immediately following the first part of exercise. 17 healthy male subjects (25.6 ± 3.7 years) volunteered to participate in this study. Peak muscle torque was determined through an allout isokinetic sprint (cadence fixed at 120 rpm) in a control condition and after two constant power output tests set to deplete 70% W in 3 and 10 min, respectively. In addition, the subjects performed two constant power output tests set to deplete 70% W in 3 and 10 min, respectively, followed by a constant test at CP + 10 W performed to exhaustion. Peak muscle torque was significantly reduced (p < 0.05) after 3 min (108 ± 19 N.m) and 10 min (112 ± 23 N.m) tests compared to the control condition (135 ± 20 N.m). However, there was no significant difference between the two experimental conditions (p > 0.05). On the other hand, the tlim at CP + 10 W was significantly longer (p > 0.05) after the 3 min test (15.8 ± 6.4 min) compared to after the 10 min test (10.0 ± 6.8 min). In conclusion, neuromuscular fatigue in the severe-intensity domain is independent of the rate of utilization of W when the same work is accumulated above the CP. However, the tlim within the severe-intensity domain can be prolonged when performed after a fast rate of utilization of W which means that the magnitude of W can be increased depending on the amplitude of power output variation above the CP.

With improving professionalism of sports around the world, the volume and frequency of training required for competitive performances at the elite level has increased concurrently. With this amplification in training load comes an increased need to closely monitor the associated fatigue responses, since maximising the adaptive response to training is also reliant on avoiding the negative consequences of excessive fatigue. The rationale for the experimental chapters in this thesis was established after considering survey responses regarding current best practice for monitoring fatigue in high performance sporting environments (Chapter 3). On the basis of the results, vertical jump assessments were selected for further investigation regarding their utility in determining neuromuscular fatigue responses. Outcomes from the subsequent series of studies aimed to provide practitioners working in high performance sport with guidelines for using vertical jumps to monitor athletic fatigue. The results from Chapter 4 indicate using the mean value of at least six jumps enhances the ability to detect small but practically important changes in performance from week to week. This study also highlighted large differences (4-6%) in morning and afternoon performance, indicating that the time of day performance is assessed needs to be accounted for when monitoring changes in jump performance. Chapter 5 explored the theory that the time of day effect observed in Chapter 4 can be explained by internal temperature differences. This theory was supported by demonstrating that an extended warm-up period can negate differences in jump performance in the morning and the afternoon. Researchers who are unable to standardise the time of day that assessment occurs are able, therefore, to control for performance differences by manipulating the warm-up protocols. The third study examined changes in vertical jump performance over a three month training period and produced several novel outcomes. A major finding was that unloaded jumps were more sensitive to neuromuscular fatigue during intensive training than loaded jumps (Chapter 6). Furthermore, this set of results showed that all subjects changed their jump technique via a reduction in the amplitude of the countermovement when they were highly fatigued. Using the same data, an analysis was performed to quantify individual differences in within-subject variation (Chapter 7) during normal and intensive training. These results provided the first indication that within-subject variability in vertical jump performance is substantially different between individuals and between different training phases, an important consideration for interpreting the practical importance of performance changes. In Chapter 8 the relationship between vertical jump performance and electrically elicited force of the knee extensors was examined to better understand the mechanism(s) of changes in jump performance associated with neuromuscular fatigue during intensive overload training. The results showed that the fatigue assessed by vertical jump performance was likely not only peripheral in origin as previously suggested by other authors. Further research is required to further understand the mechanisms of reduced performance during overload training, although the preliminary evidence presented implicates central mechanisms. To conclude the thesis, the findings presented in the experimental chapters are summarised, with a series of practical recommendations for using vertical jumps to monitor athletic fatigue presented.

Cross education is the phenomenon by which the untrained limb will experience a gain in strength following a unilateral resistance training program. However, little is known as to the underlying adaptation occurring in the untrained limb. Purpose: To examine the effect of dynamic unilateral resistance training on the strength and neuromuscular adaptations of both the trained and untrained legs. Methods: Eight previously untrained males (22.38±2.92 y, 1.73±0.08 m, 75.26±14.53 kg) completed a four-week unilateral resistance training program, while another eight untrained males (24.00±4.57 y, 1.84±0.05 m, 94.21±16.14 kg) served as controls. Isometric leg extension strength, leg press 1 repetition maximum (1RM), leg extension 1RM, root mean square of the maximal electromyographic amplitude (EMG), submaximal EMG, dynamic neuromuscular economy (NME) and the slope of NME-power output relationship were determined before and after training to assess the changes in strength and neuromuscular adaptations of the vastus lateralis (VL) and rectus femoris (RF) in both the trained and untrained legs. The unilateral resistance training program was conducted on the dominant leg (DOM) in the unilateral resistance training group (URT) and was compared to the dominant leg of the control group (CON). Cross education was measured in the nondominant leg (NON) for both groups. The unilateral resistance training program was completed three days per week for a total of twelve training sessions. Exercises included in the training program were unilateral leg press, unilateral leg extension, bilateral chest press and bilateral low row. All data was analyzed using one-way analysis of covariance of the post-testing values using the pre-testing values as the covariate. Further analysis of the EMG and NME data was performed using magnitude-based inferences. Results: The URT group improved their isometric (DOM:11.03%, NON:4.98%), leg press (DOM:77.63%, NON:64.88%) and leg extension (DOM:46.76%, NON:16.43%) strength after the four weeks of resistance training. There was no difference between the groups in isometric strength in the dominant (p=0.188) or nondominant (p=0.948) leg. For leg extension 1RM, there was a significant difference between groups in the dominant leg (p=0.018), but not the nondominant leg (p=0.482). However, there were significant group differences in both the dominant (p=0.003) and nondominant (p=0.034) leg for leg press 1RM. In terms of maximal EMG, the training groups improved in the vastus lateralis (DOM:29.81%, NON:31.44%) and rectus femoris (DOM:20.71%, NON:6.26%) individually, as well as in total EMG (DOM:24.78%, NON:17.57%). There was a Likely Positive or Very Likely Positive effect of unilateral resistance training on the changes in maximal EMG of the vastus lateralis and rectus femoris in both the dominant and nondominant legs. There was a Likely Positive effect of unilateral resistance training on the submaximal EMG of the dominant vastus lateralis at 75 and 125 watts. Conversely, in the rectus femoris, there was Unclear effects of unilateral resistance training on the submaximal EMG of the dominant leg. There was no consistent effect of unilateral resistance training on submaximal EMG values of the vastus lateralis in the nondominant leg. However, the rectus femoris in the nondominant leg experienced a Likely Positive effect of unilateral resistance training on submaximal EMG. NME improved in the URT group in the VL at 75 (DOM:9.73%, NON:13.42%), 100 (DOM:8.76%, NON:8.21%), and 125(DOM:24.26%, NON:12.8%) watts and in the RF at 75 (DOM:22.25%, NON:15.73%), 100(DOM:24.85%, NON:17.05%) and 125 (DOM:30.99%) watts. In terms of neuromuscular economy, there was a Likely Positive or Very Likely Positive effect of unilateral resistance training on most measures of NME on both the vastus lateralis and rectus femoris in both the dominant and nondominant legs. In terms of NME slope, there was only a Likely Positive effect of unilateral resistance training on the dominant vastus lateralis. Conclusion: Based on these results, it appears that the cross education of strength from unilateral resistance training is modality-specific. Furthermore, the NME of both the vastus lateralis and rectus femoris in both legs appear to improve following unilateral resistance training. However, in the nondominant leg, the improvement in NME appears to be due solely to the increase in maximal EMG, whereas the improved NME in the dominant leg is due to both an increase in maximal EMG and a decrease in submaximal EMG.
M.S.
Masters
Child, Family and Community Sciences
Education and Human Performance
Sport & Exercise Science; Applied Exercise Physiology Track

Projeto de Graduação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Licenciado em Fisioterapia
Introdução: A avaliação funcional é determinante para a prática da fisioterapia. O uso do teste de elevação do membro (TEMI) na posição supinada, de forma ativa e passiva, permite avaliar a funcionalidade da musculaturaposterior da coxa. Objetivo: Comparar o TEMI ativo e passivo, e de que forma este se correlacionaria com a performance neuromuscular. Metodologia: Análise cinemática do TEMI ativo e passivo, com captura de análise do movimento 3D através do Qualisys Oqus Camera Series (Qualisys), e avaliação da força da musculatura do joelho através do Dinamómetro Isocinético Byodex System 4 Pro™ (Byodex). Resultados: Na avaliação da comparação do TEMI ativo com o TEMI passivo, só se obteve uma diferença estatisticamente significativa (p=0,01), na amplitude máxima de teste, entre a abdução/adução realizada de forma ativa e passiva do membro inferior esquerdo.. Na avaliação da força isocinética, nenhum dos parâmetros avaliados teve uma diferença estatisticamente significativa não existindo qualquer correlação com o TEMI ativo e passivo. Conclusão: Não existem diferenças significativas entre o TEMI ativo e passivo, e os valores deste, não parecem influenciar a performance neuromuscular.
Introduction: Functional assessment is essential for physical therapy practice. The use of the lower limb elevation test (TEMI) in the supinated position, in an active and passive way, allows to evaluate the functionality of the posterior muscles of the thigh. Objective: To compare active and passive TEMI, and how this would correlate with neuromuscular performance. Methodology: Kinematic analysis of active and passive TEMI, with capture of 3D movement analysis through the Qualisys Oqus Camera Series (Qualisys), and evaluation of knee muscle strength through the Byodex System 4 Pro Is Isokinetic Dynamometer (Byodex). Results: In the evaluation of the comparison of the active TEMI with the passive TEMI, only a statistically significant difference (P = 0.01) was found in the maximal test amplitude between abduction/adduction of the left lower limb performed actively and passively. In the evaluation of isokinetic strength, none of the parameters evaluated had a statistically significant difference and there was no correlation with active and passive TEMI. Conclusion: There are no significant differences between active and passive TEMI, and their values do not seem to influence neuromuscular performance.
N/A

Carnosine (β-alanyl-L-histidine), a histidine containing dipeptide, is one of the most abundant small-molecular compounds in human skeletal muscle. Supplementation with the rate limiting amino acid, β-alanine, has resulted in significant improvements to high-intensity exercise performance. The role of carnosine as an intracellular pH buffer is undisputable, yet other physiological roles have been proposed, including the potential influence of increased carnosine content on regulation of skeletal muscle calcium (Ca2+) kinetics. The movement of Ca2+ is vital during both skeletal muscle contraction and relaxation phases. The overall aim of this thesis was to investigate the effect of β-alanine supplementation on voluntary and electrically evoked contractile properties of in-vivo human skeletal muscle. To examine this research question, there were several aims of this thesis, initially to examine the effect of β-alanine supplementation on intrinsic in-vivo isometric knee extensor force production and skeletal muscle contractility in both fresh and fatigued human skeletal muscle in young (Studies 1 and 2; Chapters 4 and 5) and older (Study 3; Chapter 6) adults. The distribution of the carnosine molecule across subcellular fractions within rat skeletal muscle tissue was explored, as well as the impact of increased carnosine availability on ATPase activity, a measure associated with skeletal muscle relaxation, estimated by Pi generation. In young adults, 28-days of β-alanine supplementation did not significantly influence voluntary and evoked force responses, or the force-frequency relationship, the in-vivo analogue of the force-Ca2+ relationship, in either fresh (Studies 1 and 2; Chapters 4 and 5) or fatigued (Study 2; Chapter 5) skeletal muscle. Furthermore, older adults experiencing pre-existing declines in skeletal muscle function due to ageing, demonstrated no beneficial effect of 28-days β-alanine supplementation on voluntary or electrically evoked skeletal muscle contractions (Study 3; Chapter 6). In young adults, there was, however, a significant decline in skeletal muscle half-relaxation time (HRT) during electrically evoked octet contractions, resting and potentiated twitches (Studies 1 and 2; Chapters 4 and 5). Two possible steps influence skeletal muscle relaxation speed include the Ca2+ removal from the myoplasm and Ca2+ dissociation from troponin followed by cross-bridge detachment. Based on the in-vivo research, it was proposed that there was a direct or indirect mechanism associated with activity of the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) pump, the proposed rate-limiting step of muscle relaxation. In-vitro analysis of ATPase activity demonstrated that SERCA activity was unaffected by increased carnosine concentrations, although there was a significant increase in overall ATPase activity (Study 4; Chapter 7). The results in this thesis showed that β-alanine supplementation was effective in improving skeletal muscle HRT in young adults, although not in healthy older adults. The exact mechanism associated with the in-vivo decline in skeletal muscle HRT remains unclear, yet raising the availability of carnosine in-vitro, does increase overall ATPase activity, although not Ca2+-dependent or SERCA activity.

Assessments of skeletal muscle functional capacity or bilateral muscular asymmetry often necessitate maximal contractile effort, which exacerbates muscle fatigue or injury. Tensiomyography (TMG) has been investigated in laboratory settings, as a means to assess muscle contractile function following fatigue; however observations have not been contextualised by concurrent physiological measures. TMG has more sparingly been applied in the field, with elite athletes. The aim of this thesis was to examine acute alterations and underlying variations in muscle contractile mechanics, through the application of TMG, contextualised with established physiological measures; and to apply TMG within high performance sports programmes. TMG successfully detected fatigue, evident from reduced strength, by displaying impaired muscle displacement, accompanied by elevated resting muscle tension. Greater asymmetry was detected in individuals with asymmetric strength; however, symmetry was masked during more complex tasks. Increased day-to-day variability was detected among highly trained athletes compared to recreationally active individuals. Acute training adaptations were detected, in contractile mechanics, in individual muscles. TMG could be useful in establishing fatigue status of skeletal muscle without exacerbating the functional decrements of the muscle, whilst also providing useful screening information for detecting asymmetry which may not be apparent during functional actions.

A dose response relationship between carbohydrate (CHO) ingestion and exercise performance has not been consistently reported. Additionally the underlying metabolic and neuromuscular explanations for an improvement in performance with increasing doses of CHO have not been fully explained. In Chapter 2 of this thesis 20 male cyclists completed 2 h of submaximal exercise followed by a time trial task (531 ± 48KJ). Three CHO electrolyte beverages, plus a control (water), were administered during a 2 h ride providing 0, 20, 39 or 64 g CHO·h-1 at a fluid intake rate of 1 L·h-1. Performance was assessed by time to complete the time trial task, mean power output sustained, and pacing strategy used. Mean task completion time (min:sec ± SD) for 39 g·h-1 (34:19.5 ± 03:07.1, p=0.006) and 64 g·h-1 (34:11.3 ± 03:08.5 p=0.004) of CHO were significantly faster than control (37:01.9 ± 05:35.0). The mean percentage improvement from control was -6.1% (95% CI: -11.3 to -1.0) and -6.5% (95% CI: -11.7 to -1.4) in the 39 and 64 g·h-1 trials respectively. The 20 g·h-1 (35:17.6 ± 04:16.3) treatment did not reach statistical significance compared to control (p = 0.126) despite a mean improvement of -3.7% (95% CI -8.8 to 1.5%). These data demonstrate that consuming CHO at a rate between 39 to 64 g·h-1 is likely to be optimal for most individuals looking to utilise a single source CHO as an ergogenic aid during endurance performances lasting less than 3 hrs. Attempts have been made to try and understand the acute metabolic regulation that occurs when ingesting increasing amounts of CHO. However, no one study has fully investigated the metabolic mechanisms underlying graded increments of CHO ingestion. In Chapter 3 we aimed to utilise stable isotopes and blood metabolite profiles to examine the integrated physiological responses to CHO ingestion when ingested at rates throughout the range where performance gains appear greatest. Twenty well-trained male cyclists completed 2 h constant load ride (95% lactate threshold, 185 ± 25W) where one of three CHO beverages, or a control (water), were administered every 15 min, providing participants with 0, 20, 39 or 64 g CHO·h-1 at a fixed fluid intake rate of 1L·h-1. Dual glucose tracer techniques (6,6,2H2 glucose and U13C labelled glucose) were used to determine glucose kinetics and exogenous carbohydrate oxidation (EXO) during exercise. Endogenous CHO contribution was suppressed in the second hour of exercise when consuming 39 and 64 g·h-1 in comparison to 0 g·h-1 (-7.3%, 95%CI: -13.1 to -1.6 and -11.2%, 95%CI: -16.9 to -5.5 respectively). Additionally, consuming 64 g·h-1 suppressed the endogenous CHO contribution by -7.2% (95%CI: -1.5 to -13.0) compared to the 20 g·h-1 treatment. Exogenous CHO oxidation rate increased by 0.13 g·min-1 (95%CI: 0.10 to 0.15) and 0.29 g·min-1 (95%CI: 0.27 to 0.31) when consuming 39 and 64 g·h-1 in comparison to 20 g·h-1 of CHO. Peak exogenous CHO oxidation rates were 0.34 (0.06), 0.54 (0.09) and 0.78 (0.19) g·min-1 for 20, 39 and 64 g·h-1 respectively. Plasma NEFA concentration was 0.10 (95%CI: 0.07 to 0.13), 0.12 (95%CI: 0.10 to 0.16) and 0.16 (95%CI: 0.13 to 0.19) mmol.L-1 higher when consuming 0 g·h-1 in comparison to 20, 39 and 64 g·h-1 respectively. Both 39 and 64 g·h-1 were effective at sparing endogenous CHO stores of which it is estimated that most of this is liver glycogen sparing, but the measured response was highly variable between individuals. Consuming 39 g·h-1 of CHO appears to be the minimum ingestion rate required to have a significant metabolic effect that results in an increase in performance. Recent research has indicated a key role of endogenous CHO sensing and oral glucose sensing in maintaining central drive and peripheral function during endurance exercise tasks. Consuming 39 and 64 g·h-1 of CHO elicits the greatest improvements in performance and also demonstrate a similar metabolic response. The improvement in subsequent time trial performance when consuming 39 and 64 g·h-1 coincided with significant alterations in whole body substrate usage that lead to endogenous CHO sparing at the same ingestion rates. In Chapter 4 we aimed to utilise gold standard neuromuscular function assessment techniques, alongside novel measures, to investigate the effect of consuming different rates of CHO on neuromuscular function during and following prolonged cycling exercise. In a double-blind, randomised cross-over design, well-trained male cyclists (n=20, mean±SD, age 34 ± 10 y, mass 75.8 ± 9 kg, peak power output 394 ± 36 W, V̇O2max 62 ± 9 ml·kg-1·min-1) completed 2 familiarisation trials then 4 experimental trials. Trials involved a 2 h submaximal ride followed by a high intensity time trial task lasting approx. 35 min with each of 0, 20, 39 and 64 g·h-1 CHO ingestion rates during submaximal exercise. Each trial involved pre and post exercise assessments (MVC, Mwave twitch potentiation and force, motor unit recruitment and firing rate assessment using high density EMG) and during exercise (gross EMG amplitude). MVC peak torque values were reduced post exercise by -20.4 nM (95%CI: -26.5 to -14.4) in comparison to pre value on all trials with no differences between trials. The firing rates of early recruited motor units significantly increased by 1.55 pps (95%CI: 0.51 to 2.59) following exercise in comparison to pre-exercise rates. Gross EMG during the 2 h cycling bout revealed a main effect of treatment (p<0.01) but post hoc comparisons provided no clarity and likely reflect methodological issues. Consuming CHO at ingestion rates between 20 and 64 g·h-1 had little to no impact on the neuromuscular function of well-trained cyclists when comparing pre and post fatiguing exercise values. Despite differences in time trial completion time between trials, following exercise to fatigue in an endurance task, no post exercise differences were detected.

In spite of an accumulating volume of information about injury to the musculoskeletal system in recent years, little scrutiny has been focused on the cause and prevention of injury. The large number of injuries to the knee joint and the anterior cruciate ligament ACL ligament in particular, is an alarming sign of the seriousnesso f this problem facing recreational and athletic people around the world. The large number of injuries appears to arise from an unfavourable interaction between `static' connective tissue-related and 'dynamic' muscle-related stabilisers of the joint system (Gleeson et al., 1998; Myers and Lephart, 2000). The functional stability is mediated ultimately by the neuromuscular system (Myers and Lephart, 2000) and it is important therefore to understand the function of the neuromuscular system as fully as possible in order to affect the aetiology and likelihood of injury favourably. The neuromuscular system includes biological 'machinery' offering capability for neuromuscular control (proprioception) and neuromuscular performance (motor actions). The neuromuscular control was quantified by newly-developed and laboratory-based assessmentsin volving the dynamic muscular reproduction of a `blind' target force and the error associated with such efforts may provide greater efficacy of measurement compared to those tests used in contemporary practice which may not indicate an individual's true functional capability to resist injury threats, in particular, to assessth e muscular dynamic intensity associatedw ith sporting endeavours which may functional capability to resist injury threats may be compromised. This thesis is presented as a series of three studies. The aim of this study was to examine between-day reproducibility and single measurement reliability of objective and self-perceived indices of force error in the knee flexors and extensors in men. Results showed that the reproducibility and single-measuremenrt eliability of objective (CE%, VE %) and self-perceived performance (SPCE% and SPVE %) during between-daya ssessmentso f neuromuscularc ontrol NCA1, NCA2 and NCA3 offered compromised precision and efficacy. These indices of performance should be deployed cautiously within both case-study and inter-individual comparisons and must rely on multiple-trial protocols to achieve acceptable levels of measurement precision in such circumstances. The aim of the second study was to examine the effects of serial bouts of acute fatiguing exercise on objective and self-perceived indices of neuromuscular control and performance of the knee flexors in men. In summary, results showed that despite substantial fatigue-related strength and muscle activation impairments, neuromuscular control as measured objectively by NCAI, NCA3 or RJA was not influenced significantly by the fatigue task intervention and that capability in this aspect of neuromuscular control was preserved in response to this type of exercise stress. Furthermore, constant error associated with self-perceived performance was similarly not influenced significantly by the fatigue task intervention. It is plausible that in ordert o provideo ptimump rotectiono f synovialj oints, neuromusculacro ntrol of the kneef lexorsm ay be preservedp referentiallyt o neuromusculapre rformance whenc hallengedb y fatigue-relatede xercises tresses. The third study assessedc oncomitant effects of an episodeo f muscle damage interspersed amongst serial bouts of fatigue on objective and self-perceived indices of neuromuscular control and performance of the knee flexors. This type of exercise perturbation reflects that associated with acute, transient and metabolically-focused effects (fatigue) and that during a more prolonged, mechanical type of disruption to the muscle (EIMD). It was likely to mimic some of the patterns of exercise inherent in sports and training practice and may serve to disrupt dynamic stabilization around the knee joint. Results showed that despite substantial EIMD and fatigue-related strength impairments (the former confirmed in this experiment by means of indirect physiological descriptive variables including a reduced range of movement and an increase in pain upon active movement of the affected limb), neuromuscular control as measured by objective and self-perceived indices of constant and variable error in assessment protocols NCA 2, NCA3 and DNCA was not influenced significantly by the EIMD and fatigue task intervention. It was notable that capability in this aspect of neuromuscular control was preserved in response to this type of exercise perturbation in the three different modes of objective assessments of neuromuscular control used in this study.

Study 1: The contribution of strength characteristics to change of direction and agility performance in female basketball athletes Research has often examined the relationship between one or two measures of strength and change of direction (COD) ability, reporting inconsistent relationships to performance. These inconsistences may be the result of the strength assessment utilized and the assumption that one measure of strength can represent all “types” of strength required during a COD task. Therefore the purpose of this study was to determine the relationship between several lower body strength and power measures, COD, and agility performance. Twelve (n=12) female basketball athletes completed a maximal dynamic back squat, isometric mid-thigh pull, eccentric and concentric only back squat, and a counter-movement jump, followed by two COD tests (505 and T-Test) and a reactive agility test. Pearson product moment correlation and stepwise regression analysis were performed on all variables. The percentage contribution of each strength measure to an athlete’s total strength score was also determined. Our results demonstrated that both COD tests were significantly correlated to maximal dynamic, isometric, concentric and eccentric strength (r = -0.79 to -0.89), with eccentric strength identified as the sole predictor of COD performance. Agility performance did not correlate with any measure of strength (r = -0.08 to -0.36), while lower body power demonstrated no correlation to either agility or COD performance (r = -0.19 to -0.46). These findings demonstrate the importance of multiple strength components for COD ability, highlighting eccentric strength as a deterministic factor of COD performance. Coaches should aim to develop a well-rounded strength base in athletes; ensuring eccentric strength is developed as effectively as the often-emphasized concentric or overall dynamic strength capacity. Study 2: Mechanical determinants of faster change of direction and agility performance in female basketball athletes Change of direction (COD) and agility require the integration of multiple components to produce a faster performance. However, the mechanisms contributing to a faster performance without the confounding factor of athlete expertise or gender is currently unknown. Therefore, the purpose of this study was to assess body composition, strength and kinetic profile required for a faster COD and agility performance across multiple directional changes. Six faster and six slower (n=12) elite female basketball athletes completed a maximal dynamic back squat; eccentric and concentric only back squat; isometric mid-thigh pull; whole body scan to determine lean, fat and total mass; 505 COD test; T-Test; and a multidirectional agility test over in-ground force plates to obtain relevant kinetic measures. Group (faster and slower) by test (2x3) MANOVA’s with follow up ANOVA’s were conducted to examine differences between faster and slower groups and each COD and agility test (p ≤ 0.05). Faster athletes during the 505 COD test produced significantly greater vertical force (p = 0.002) and eccentric and isometric strength capacity (p = 0.001). Faster agility and T-Test athletes demonstrated significantly shorter contact times (p = 0.001), greater propulsive impulse (p = 0.02), isometric strength, and relative lean mass compared to slower athletes. Differences between faster athletes across each test appear to be attributed to the mechanical demands of the directional change, increasing force and impulse application as the degree of directional change increased. These findings indicate that different mechanical properties are required to produce a faster COD and agility performances, and the importance of a greater strength capacity to enable greater mechanical adjustment via force production and body control, during different directional changes. Study 3: Neuromuscular strategies contributing to faster multidirectional agility performance The aim of this study was to first determine differences in neuromuscular strategy between a faster and slower agility performance, and second compare differences in muscle activation strategy employed when performing two closely executed agility movements. Participants recruited from an elite female basketball team completed an ultrasound to determine quadriceps muscle-cross sectional area; reactive isometric mid-thigh pull to determine the rate of muscle activation, rate of force development, pre-motor time and motor time; and multidirectional agility tests completing two directional changes in response to a visual stimulus. Peak and average relative muscle activation of the rectus femoris, vastus medialis, vastus lateralis, biceps femoris, semitendinosus and gastrocnemius were measured 100 ms prior to heel strike (pre-heel strike) and across stance phase for both directional changes. Faster agility performance was characterized by greater pre-heel strike muscle activity and greater anterior muscle activation during stance phase resulting in greater hip and knee extension increasing propulsive impulse. Differences between directional changes appear to result from processing speed, where a greater delay in refractory times during the second directional change resulted in greater anterior muscle activation, decelerating the body whilst movement direction was determined

Increased relative risk of non-contact anterior cruciate ligament (ACL) injury has been attributed to numerous biomechanical, anatomical and neuromuscular factors. Females are at greater relative risk of non-contact ACL injury compared with males. Dynamic knee stability is an important component required to reduce relative risk of injury, especially to the knee joint. It is difficult to directly measure knee stability; however the eccentric ability of the hamstrings to co-contract to counter the torque produced by concentric quadriceps actions during knee extension is important in stabilising the knee (determined as the functional H/Q ratio [FH/Q]). One of the proposed reasons for a greater incidence of non-contact ACL injury in females is a reduced capacity for neuromuscular functioning to stabilise the knee joint effectively. Most injuries occur in the second half of an athletic event when fatigue is commonly present, therefore identifying fatigue as a potential risk factor for ACL injury and this may allow for the development of improved prevention strategies. The three experimental studies included within this thesis (chapter 4-6) have generated novel data on sex differences in the FH/Q ratio and neuromuscular performance prior to and following a downhill running fatigue task. One hundred and ten healthy males (n=55; mean ± SD 29 ± 5 yrs) and females (n=55; mean ± SD 27 ± 6 yrs) were recruited from the university population. Isokinetic torque of the hamstrings and quadriceps was determined at 60, 120 and 240˚·s–1with the hip flexed at 0°. Range of movement of the knee joint was 90° with 0° determined as full volitional extension. Concentric (CON) torque was determined first followed by eccentric (ECC) torque, with the slowest velocity tested first. Torque was gravity corrected and filtered to only include constant velocity periods. For functional relevance FH/Q ratio was determined at 15, 30, 45º (as these are the joint angles where injury is most likely to occur) and where peak torque (PT) was achieved (to compare with the extant literature) for each movement velocity. Surface electromyography was recorded from the semitendinosus (ST), semimembranosus (SM) and biceps femoris (BF) of the dominant limb using an 8-channel DelSys EMG telemetry system. The biodex square wave synchronization pulse was configured with the EMG software via a trigger system so that EMG and torque data were completely time aligned. Raw EMG data were collected at a sampling frequency of 1024 Hz and included a common mode rejection ratio of <80 dB and an amplifier gain of 1000. Raw EMG data was band pass filtered at 20 – 450 Hz. The electromechanical delay (EMD) was determined as the time delay between the onset of muscle activation (change in activation of +15 μV) and onset of torque production (9.6 N·m) according to the procedures described by Zhou et al (1995). The aim of the first study (chapter 4) was to explore sex differences in the FH/Q ratio whilst taking into account joint angle and movement velocity. A 2 (sex) x 3 (movement velocity) x 4 (joint angle) ANOVA was performed to determine interactions and main effects. FH/Q ratio ranged from 59 to 98% in females and 66 to 109% in males across joint angles and movement velocities. No significant differences between males and females in age but males were significantly taller and had greater body mass. Irrespective of sex the FH/Q ratio increased with joint angle and movement velocity to improve knee stability during high velocity movement and near full extension. However, the FH/Q ratio is significantly lower in females compared with males and importantly this sex difference increases as movement velocity increases. Females have a lower FH/Q ratio than males close to full knee extension and during high velocity movements, both of which are predisposing factors for increased injury risk. This reduced FH/Q ratio may impair dynamic knee stability in females during fast velocity movements and may predispose them to a greater relative risk of knee injury. The aim of the second study (chapter 5) was to examine sex differences in the EMD of the hamstring muscles during eccentric muscle actions at 60, 120 and 240˚·s–1. A 2 (sex) x 3 (muscle group) x 3 (movement velocity) ANOVA was performed to determine interactions and main effects. During eccentric hamstring muscle actions there were no differences in the EMD of the 3 muscles examined. Irrespective of sex, significant main effects for angular velocity was demonstrated, indicating an increase in the delay time with increasing angular velocity. This increased delay during fast velocity movements may account for the increased risk of injury during fast movements. No significant sex differences in EMD was found irrespective of movement velocity of muscle examined, suggesting that females do not have impaired neuromuscular performance of the hamstring compared with males during eccentric hamstring muscle actions in the rested state. The aim of the third study (chapter 6) was to examine the effects of a fatigue task on sex differences of the FH/Q ratio and EMD. The procedures used in study 1 and 2 were repeated pre and post a downhill running fatigue task to explore fatigue related effects on neuromuscular functioning. Each participant performed a 40 min intermittent downhill running protocol consisting of 5 × 8 min bouts on a -10% decline, with 2 min standing rest between each bout. Irrespective of sex, joint angle or angular velocity, the FH/Q ratio was lower and EMD of hamstrings muscle was longer post-fatigue compared to pre-fatigue. Significant interactions between sex and time (pre-post) for the FH/Q ratio and EMD of hamstring muscles were found. The interactions showed a significantly lower FH/Q ratio and significantly longer EMD post fatigue in females compared to males. These data suggest that functional stability of the knee is reduced when fatigue is present and the impact of fatigue is greater in females. The findings of this thesis indicate the importance of determining the FH/Q ratio using angle specific torque as well as taking into account movement velocity, rather than simply using PT values to monitor muscle function of the knee. The findings of the present thesis support the notion that fatigue compromises the stability of the knee by reducing the FH/Q ratio and lengthening EMD. These effects are greater in females compared to males and may predispose them to greater relative risk of injury. Therefore, movement velocity, joint angle and fatigue resistance all need to be considered when designing training programmes to reduce the relative risk of injury. The focus of such training should be aimed at eccentric conditioning of the hamstring muscles to improve both muscular and neuromuscular functioning to limit the fatigue related effects, especially in females.

The frequency of anterior cruciate ligament injuries (ACL) by non-contact aetiologies (Rees, 1994) and the potentially severe consequences for the team games player (Kujala et al., 1995) has underscored the need for understanding of the importance of neuromuscular mechanisms in the effective maintenance of knee joint integrity (Gleeson et al., 1998a). In particular, the knee flexor muscle group offers greatest dynamic protection against injuries to this ligament (Johansson, 1991). Traditional (volitional) methods of assessment of neuromuscular performance can be confounded by inhibitory mechanisms (Gleeson, 200 1). Accordingly, the painless technique of magnetic stimulation of peripheral nerves has received increased attention for the assessment of aspects of 'true' neuromuscular capacity (King and Chippa, 1989). There is accumulating evidence that implies a linkage between fatigue and injury (Gleeson et al., 1998b; Hawkins et al., 2001). However, further investigation is required to explore how such exercise may affect 'true' performance capacity and the possible implications for knee joint stability. Estimates of indices of neuromuscular performance, such as electromechanical delay, rate of force development and time to half peak force, may offer important information concerning the temporal capabilities of the active joint stabilisers, to initiate and muster meaningful levels of muscle force. These estimates may also provide an insight into the likely knee injury avoidance capabilities (Gleeson et al., 1998b; Mercer et al., 1998). However, only limited information is available in the contemporary scientific literature regarding the reproducibility and reliability characteristics of these indices of performance for the knee flexors, particularly subsequent to magnetic stimulation.

Whole body vibration (WBV) is a mode of exercise by which an individual stands on a vibration platform that may be oscillating and therefore creating vertical displacement which affects gravitational forces acting upon the whole body. Manipulations of platform amplitude or frequency can affect the rate of change of the WBV (i.e. acceleration) acting upon an individual. The specific influences of frequency or amplitude, however, are unknown. The aim of the study, therefore, was two fold; (1) to identify chronic WBV effects of neuromuscular performance within a community dwelling older adult sample, and; (2) to identify WBV methods that would elicit chronic neuromuscular performance changes within such a sample. The study incorporated a randomised controlled experimental design to examine the aim. Seventy-three community dwelling older adults freely consented to the requirements of the study (mean age = 72.0 years). Neuromuscular performance was quantified with the 5-Chair Stands test, the Timed Up and Go (TUG) test and the Tinetti test. Health Related Quality of Life (HRQOL) was qualified with the SF-36 Health Survey. A six week WBV intervention significantly changed the quantifiers of neuromuscular performance in a community dwelling older adult sample. The WBV intervention significantly reduced time taken to complete the 5-Chair Stands test (p <.05) and the TUG test (p <.05). The six week WBV intervention significantly improved Tinetti test scores (p <.05). The six week WBV intervention significantly improved all components of HRQOL. For the 5-Chair Stands test, a three WBV sessions per week intervention elicited significantly larger (p <.05) neuromuscular performance gains than a two WBV sessions per week intervention in the target sample. For the TUG test, a three WBV sessions per week intervention elicited significantly larger (p <.05) neuromuscular performance gains than a zero and one WBV session per week intervention in the target sample. A significant difference (p <.05) was found between pre-test and post-test Tinetti test scores for all WBV intervention groups. There was an insignificant difference (p >.05) found within the control group of community dwelling older adults for the Tinetti test. Detraining effects were observed three weeks after the cessation of the six week WBV intervention for the three WBV sessions per week group. Neuromuscular performance reduced after the detraining period. Vibration platform dynamics (manipulated frequency and controlled amplitude) showed that gravitational forces created by the WBV were safe since no injuries were associated with the intervention and since participant compliance was 100% during the six week WBV intervention. The methods of this study showed a chronic WBV intervention to be a safe and easily administered exercise to improve neuromuscular performance and HRQOL of a community dwelling older adult sample. Specifically, WBV could be used as a safe and effective tool to improve aspects of normal daily function such as body balance and gait speed.

Abstract The purpose of this study was to examine thermal (body temperature, thermal sensation and comfort ratings), circulatory (blood pressure, heart rate variability) and neuromuscular performance responses to whole-body cryotherapy (WBC, -110 °C). Altogether 66 healthy subjects were exposed to WBC for two minutes. The acute and long-term changes were examined, when the subjects were exposed to WBC three times a week during three months. Skin temperatures decreased very rapidly during WBC, but remained such a high level that there was no risk for frostbites. The effects on rectal temperature were minimal. Repeated exposures to WBC were mostly well tolerated and comfortable and the subjects became habituated at an early stage of trials. WBC increased both systolic (24 mmHg) and diastolic (5 mmHg) blood pressures temporarily. Adaptation of blood pressure was not found during three months. The acute cooling-related increase in high-frequency power of RR-intervals indicated an increase in cardiac parasympathetic modulation, but after repeated WBC the increase was attenuated. The repeated WBC exposure-related increase in resting low frequency power of RR-intervals resembles the response observed related to exercise training. There are signs of neuromuscular adaptation, especially in dynamic performance. A single WBC decreased flight time in drop-jump exercise, but after repeated WBC these changes were almost vanished. This adaptation was confirmed by the change of the activity of the agonist muscle, which increased more and the change of the activity of antagonist muscle, which increased less/did not change after repeated WBC indicating reduced co-contraction and thus, neuromuscular adaptation.

Thesis (M.A.)--University of North Carolina at Chapel Hill, 2006.
Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of the requirements for the degree of in the Department of Exercise and Sport Science (Athletic Training)." Discipline: Exercise and Sports Science; Department/School: Exercise and Sport Science.

Aim The aim of this study was to investigate the effect of flywheel resistance training on functional neuromuscular performance in physically active youth.   Method Forty-four healthy and physically active youth between 12-14 years of age (n=19 boys & n=25 girls) volunteered to participate and were randomized into three different groups of flywheel resistance training (FRT) (n=15, body mass = 42,9 ± 8,6 kg, time to Peak Height Velocity (PHV) = - 0,8 ± 1,6), traditional strength training (TST) (n=15, body mass = 44,7 ± 10,3 kg, time to PHV = - 0,8 ± 1,5) and a control group (CON) (n=14, body mass = 43,8 ± 9,0 kg, time to PHV- 0,8 ± 1,5. Squat jump (SQ), Countermovement jump (CMJ), 10-m acceleration, 20-m speed and 30-sprint was assessed pre- and post-intervention. All training groups performed 12 resistance training sessions over a 6-week intervention. The FRT-group performed bilateral flywheel resistance squats with 4 sets of 6 repetitions with 0,025 to 0,05 kgm2 and the TST-group performed bilateral barbell squats with 4 sets of 6 repetitions at a predicted 80 %1RM, while the control group only performed their regular sports training.   Results Repeated measures two way-ANOVA, 3 x 2 (training group x time), showed no significant mean effects between groups after the intervention. A significant increase occurred in the control group for SQ; 2,4 ± 2,5 (cm) p ≤ 0,008 and CMJ; 2,2 ± 3,1 (cm) p ≤ 0,037. Both training groups increased significantly in body mass from pre- to post-tests by 2,0 ± 2,7 kg for the flywheel training group and 1,3 ± 0,9 kg in the traditional strength training group (p ≤ 0,05).   Conclusions This study indicates that flywheel training can be used as a resistance training method for youth athletes without inducing training related injuries. Flywheel resistance training resulted in a small but non-significant increase from pre to post test in squat jump and 10-m sprint. Future studies on flywheel resistance training for youth needs to investigate the implementation of longer training periods, additional training sessions, more experienced youth in resistance training and faster movement speed.

Whole body vibration (WBV) is a mode of exercise by which an individual stands on a vibration platform that may be oscillating and therefore creating vertical displacement which affects gravitational forces acting upon the whole body. Manipulations of platform amplitude or frequency can affect the rate of change of the WBV (i.e. acceleration) acting upon an individual. The specific influences of frequency or amplitude, however, are unknown. The aim of the study, therefore, was two fold; (1) to identify chronic WBV effects of neuromuscular performance within a community dwelling older adult sample, and; (2) to identify WBV methods that would elicit chronic neuromuscular performance changes within such a sample. The study incorporated a randomised controlled experimental design to examine the aim. Seventy-three community dwelling older adults freely consented to the requirements of the study (mean age = 72.0 years). Neuromuscular performance was quantified with the 5-Chair Stands test, the Timed Up and Go (TUG) test and the Tinetti test. Health Related Quality of Life (HRQOL) was qualified with the SF-36 Health Survey. A six week WBV intervention significantly changed the quantifiers of neuromuscular performance in a community dwelling older adult sample. The WBV intervention significantly reduced time taken to complete the 5-Chair Stands test (p .05) found within the control group of community dwelling older adults for the Tinetti test. Detraining effects were observed three weeks after the cessation of the six week WBV intervention for the three WBV sessions per week group. Neuromuscular performance reduced after the detraining period. Vibration platform dynamics (manipulated frequency and controlled amplitude) showed that gravitational forces created by the WBV were safe since no injuries were associated with the intervention and since participant compliance was 100% during the six week WBV intervention. The methods of this study showed a chronic WBV intervention to be a safe and easily administered exercise to improve neuromuscular performance and HRQOL of a community dwelling older adult sample. Specifically, WBV could be used as a safe and effective tool to improve aspects of normal daily function such as body balance and gait speed.

The primary objective of this study was to analyze the relationship between testosterone levels and vertical jumping performance in elite men and women athletes. The secondary objective was to verify whether testosterone levels and vertical jumping performance were different in men and women athletes and if those measurements were different between different athletic groups. Seventy (22 women and 48 men) elite athletes in track and field (sprinters), handball, volleyball, and soccer competing at national and international levels participated in the study. After 10 hours of fasting and 1 day of rest, blood samples were drawn from the antecubital vein for determining testosterone levels. Vertical jumping tests consisted of counter-movement jumps conducted on a resistive platform connected to a digital timer. Resting testosterone levels in women were 9.5% of those of the men (respectively 0.62 ± 0.06 ng·ml−1 and 6.49 ± 0.37 ng·ml−1; p < 0.001). Countermovement jump performance was significantly different between women and men athletes, with women's jumping ability 86.3% of that of men (p < 0.001). A significant positive relationship was identified between testosterone levels and vertical jump performance when all data where considered (r = 0.61, p < 0.001, n = 70). The primary objective of this study was to analyze the relationship between testosterone levels and vertical jumping performance in elite men and women athletes. The secondary objective was to verify whether testosterone levels and vertical jumping performance were different in men and women athletes and if those measurements were different between different athletic groups. Seventy (22 women and 48 men) elite athletes in track and field (sprinters), handball, volleyball, and soccer competing at national and international levels participated in the study. After 10 hours of fasting and 1 day of rest, blood samples were drawn from the antecubital vein for determining testosterone levels. Vertical jumping tests consisted of counter-movement jumps conducted on a resistive platform connected to a digital timer. Resting testosterone levels in women were 9.5% of those of the men (respectively 0.62 ± 0.06 ng·ml−1 and 6.49 ± 0.37 ng·ml−1; p < 0.001). Countermovement jump performance was significantly different between women and men athletes, with women's jumping ability 86.3% of that of men (p < 0.001). A significant positive relationship was identified between testosterone levels and vertical jump performance when all data where considered (r = 0.61, p < 0.001, n = 70).

The rapid growth of an older demographic is an increasing concern around the world. Older people have been reported to suffer from physiological and neuromuscular declines in several systems including skeletal muscles, central nervous system, cardiovascular processes and respiratory function. These age-related changes are often reflected through impairments in functional performance of occupational tasks as well as activities of daily living. This may make an older population more prone to musculoskeletal disorders and injuries. In addition, health problems and injury risks are likely amplified by factors such as obesity. Obesity has emerged as a serious health concern in the United States in recent decades. However, obesity-related changes in performance and motor control as well as how they will be modified by gender, specifically among older adults, are still largely unexplored. As motor variability has recently been reported to be associated with fatigue development and may have the potential to reveal underlying mechanisms of neuromuscular control, the main goals of this study were to investigate the influence of gender and obesity on motor performance, neuromuscular control and endurance in the elderly, by examining differences in motor variability during intermittent submaximal isometric exertions of the knee and hand. Fifty-two older participants with age over 65 were recruited into four groups: obese male (9), obese female (13), non-obese male (15) and non-obese female (15). The obese groups consisted of those whose BMI was greater than 30 kg/m2. Participants were asked to perform intermittent (15s on and 15s off) isometric handgrip and knee extensions at 30% MVC until exhaustion. Force and muscle activations of the Vastus Lateralis, Rectus Femoris, Extensor Carpi Radialis and Flexor Carpi Radialis muscles were collected through the endurance task. Motor variability was quantified using the coefficient of variation (CV) and sample entropy (SaEn) of the surface electromyography (EMG) and force signals. Motor variability during exercise differed both between males and females, and between obese and non-obese people, reflecting different motor strategies employed in order to prolong endurance. Overall, across all individuals, we observed a significant positive correlation between cycle-to-cycle variability of knee extensor muscle activation during the baseline period of the task and endurance time. As for gender differences, males exhibited longer endurance times than females, and seemed to achieve that through utilizing a motor strategy involving a more variable (higher CV) and less complex (lower SaEn) agonistic muscle activity. Since this was accompanied by a lower fluctuation in the force signal (lower CV) and a higher complexity of force (SaEn), we interpreted this to be a motor strategy involving more variable recruitment of synergistic and antagonistic motor units during the knee extension task to prolong endurance time, among males compared to females. As for obesity differences, there were no obesity-related changes in endurance time. However, obese individuals exhibited a greater cycle-to-cycle variability that was positively correlated with endurance time during the knee extension task, indicating a larger alteration in the recruitment of motor units across successive contractions, which contributed to comparable endurance time and performance with their non-obese counterparts. During the hand-grip tasks, variabilities in force and muscle activity followed similar trends as the knee extension task. However, there were no significant gender or obesity differences in endurance time, and there also weren't any significant correlations between any of the dependent variables with endurance time. Thus, this study was a basic investigation into changes in motor variability and how it was associated with the development of fatigue among older adults; and the potential influences of gender and obesity on the relationships. Two tasks of high relevance to both occupational life and activities of daily living, i.e. knee extension and hand-grip were considered. Our findings enhance the theoretical understanding of the underlying neuromuscular control patterns and their relationship with fatigue for different individuals. Given that both aging and obesity rates are rising continuously and becoming a substantial health and safety problem especially in the occupational environment, the results from this study are both timely and critical for practical design applications, especially by recognizing the importance of having a variable motor pattern in task performance, even among older adults.
MS

The first purpose of this research was to establish the reliability of numerous measures obtained from a single and short duration repeated countermovement jump (CMJ) utilising a portable forceplate (Experimental Studies 1 and 2). Secondly, the response of reliable CMJ variables and T, C and T:C to a single elite level ARF match was assessed to identify the pattern of response and highlight those measures with the greatest potential for usefulness as monitoring tools across longer periods (Experimental Study 3). Finally, those variables identified as most valuable in Experimental Study 3 in addition to T, C and T:C; were measured throughout a season of elite ARF competition in order to examine the manner of their response and assess the magnitude of change in these variables in relation to performance and training and competition loads (Experimental Study 4).

Neuromuscular fatigue is an inevitable process at play during prolonged exercise, and may be caused by multiple alterations within the central nervous system and peripheral musculature. As fatigue develops, the neuromuscular system must adapt to these changes by making compensatory movement pattern adjustments so as to use motor pathways that are less fatigued in an effort to maintain task performance; motor variability is thus increased. The primary purpose of the four studies contained within this doctoral thesis was to detail the progression of exercise-induced neuromuscular fatigue, and to improve our understanding of the muscle activation and joint kinematic alterations that occur as fatigue accumulates. Within this context, cycling was used as the exercise model, and the relationship between physiological and biomechanical aspects of high-intensity, moderate duration (<10 >min) cycling were specifically examined. The first two studies of this thesis were aimed at understanding the progression of neuromuscular fatigue as well as the associated motor control and biomechanical (i.e. muscle activation and kinematic) changes that occur during exhaustive cycling. Specifically, the time course and relative contributions of central and peripheral fatigue mechanisms, and the associated changes in muscle activation and both lower (i.e. hip, knee and ankle joint) and upper (i.e. trunk) limb kinematics were examined during a high-intensity cycling time to exhaustion (TTE) test. This was performed at 90% maximal aerobic power (Pmax) with nine well-trained cyclists. Temporal relationships between joint kinematics and changes in markers of central and peripheral fatigue were also examined. Peripheral fatigue (i.e. impaired contractile function: reduced peak twitch torque, −39.9%; twitch contraction time, −10.7%; and the average rates of twitch torque development −34.7% and relaxation −36.7% at task failure i.e., T100) developed early in the exercise bout from 60% of the time to task failure (p < 0.05). However, a central facilitation, measured as an increase in peak vastus medialis (38.9%) and gluteus maximus electromyogram (87.2%) amplitudes at T100, rather than central fatigue, occurred towards the end of the exercise task (p < 0.05). Thus, neuromuscular fatigue development was associated with an increase in the magnitude of lower limb muscle activity, which may have represented an attempt to increase muscle force to maintain the required power output of the cycling task. Increases in trunk flexion were observed from 60% of the time to task failure (p < 0.05), and were therefore notable at or after the point of significant peripheral fatigue. Conversely, increases in trunk medio-lateral sway (lateral flexion), hip abduction/adduction and knee valgus/varus were observed only from 80% of the time to task failure (p < 0.05), which paralleled the increase in central motor drive. The results of this study therefore indicate that significant trunk kinematic changes in the sagittal plane occurred at or after the point of significant peripheral fatigue development, whereas, significant changes at the trunk, hip and knee joints in the coronal plane occurred later in the exercise task and paralleled the facilitation of central motor drive during the cycling task. In the third study, the effects of real-time, kinematic feedback provision for trunk flexion (TTETflex), trunk medio-lateral sway (TTETsway) and hip abduction/adduction (TTEHabd/add) during a high-intensity TTE cycling test (90% Pmax) in nine well-trained cyclists were examined. The times taken to reach task failure were compared to a TTE test completed with no feedback. The times taken to reach task failure were not significantly different when provided with trunk flexion (TTETflex) and hip abduction/adduction (TTEHabd/add) feedback compared to the non-feedback condition (p > 0.05). There was, however, a significant decrease in the time to task failure during the TTETsway test (p < 0.05). Not all participants could maintain trunk and/or hip movement within a set movement pattern criteria; and three participants were therefore excluded from the kinematic analyses for both the TTETflex and TTETsway tests (n = 6) as were two participants from the TTEHabd/add test (n = 7). For participants who correctly used the kinematic feedback, no differences in the times taken to reach failure were observed in between the feedback (TTETflex, TTETsway and TTEHabd/add) and nonfeedback test conditions (p > 0.05). Despite being given feedback, changes in joint kinematics were similar across all test conditions; significant alterations were observed at the trunk and knee joints in the sagittal plane and at the hip and knee joints in the coronal plane (p < 0.05). Given trunk flexion feedback (TTETflex), significant increases in left hip flexion and trunk medio-lateral sway ROM were observed (p < 0.05), whereas given trunk medio-lateral sway feedback (TTETsway), increases in right hip flexion ROM also occurred (p < 0.05). These results indicate that, regardless of whether or not well-trained cyclists are able to control the level of kinematic variability when fatigued, acute exposure to real-time kinematic feedback to limit trunk or hip movement during high-intensity cycling may influence cycling kinematics (i.e. technique) and, in some cases (e.g. trunk medio-lateral sway), may reduce performance. The final study examined the relationship between joint kinematics, measured in non-fatigued and fatigued high-intensity cycling, and the cyclists’ physiological profiles (i.e., physiological attributes indicative of successful cycling ability, including both maximal oxygen consumption and peak power output relative to body mass, maximal heart rate, both power output and heart rate at the first and second ventilatory thresholds and cycling economy at 100 W) and the time taken to reach task failure. Submaximal physiological attributes were correlated with hip (abduction/adduction angle and ROM), knee (flexion angle) and ankle (flexion ROM) kinematics measured in a non-fatigued state at the start of the trial (r > 0.40; p < 0.05). However, both physiological attributes associated with maximal exercise capacity and cycling economy were correlated with trunk (flexion angle) and ankle (flexion angle and ROM) kinematics measured in a fatigued state at the end of the test (r > 0.40; p < 0.05). Trunk flexion and medio-lateral sway ROM in a non-fatigued state, and trunk flexion angle in a fatigued state, were associated with the time to task failure (r > 0.50; p < 0.05). Thus, the degree of trunk flexion and medio-lateral sway may be important kinematic variables that are indicative of cycling performance. These findings reveal an interdependence between cycling kinematics and both the physiological attributes indicative of successful cycling performance and the time taken to reach task failure during high-intensity, constant-load cycling. In conclusion, the findings presented in this thesis indicate that the temporal patterns of central and peripheral neuromuscular fatigue differ (Study 1; Chapter 3). Task failure during high intensity cycling appears to be associated with the development of peripheral fatigue despite the presence of an increase in central motor drive. Subsequent to the development of neuromuscular fatigue, muscle activation and joint kinematic alterations can be observed, which may represent compensatory mechanisms employed by the neuromuscular system to continue task performance (Studies 1 and 2; Chapters 3 and 4). Joint kinematic alterations in the sagittal plane were associated with the development of peripheral fatigue whereas coronal plane adjustments occurred in parallel with central facilitation, and/or when a more substantial level of peripheral fatigue accumulated. Such compensatory kinematic strategies are also associated with an athlete’s physiological attributes and their cycling performance (i.e., time to task failure) (Study 4; Chapter 6). Importantly, imposing specific joint kinematic restrictions (trunk flexion, trunk medio-lateral sway and hip abduction/adduction) during exhaustive cycling, influenced cycling kinematics (i.e. technique) and, in some cases (e.g. trunk medio-lateral sway), reduced the time taken to reach task failure for well-trained cyclists (Study 3; Chapter 5). Such findings enhance our understanding of how the neuromuscular system copes with fatigue development, and should assist coaches and/or occupational health practitioners to better understand the fatigue process and neuromuscular strategies utilised during exercise tasks with similar characteristics to that used in the current studies.

Exercise-induced fatigue is a complex, multifactorial process, the physiological bases of which are still widely debated. Recent research has implicated pain sensation in the aetiology of exercise-induced neuromuscular fatigue. Indeed, acute consumption of acetaminophen (ACT, or paracetamol), a non-specific inhibitor of the cyclooxygenase (COX) enzymes which synthesise prostaglandins and sensitise group III/IV muscle afferents, has been shown to improve exercise performance concomitant with a lower pain and effort sensation. However, the neurophysiological bases for the potential ergogenic effect of acute ACT ingestion, and how this influences the power/torque-duration relationship, have yet to be determined. Therefore, the purpose of this thesis was to assess the effect of acute consumption of the recommended therapeutic dose (1 g of ACT and 400 mg of IBP) of common pain-relieving, COX-inhibiting medicines on performance and the mechanisms of neuromuscular fatigue development in a variety of different exercise tests. Study 1: Mean torque (61 ± 11 vs. 58 ± 14% pre-exercise MVC) and end-test torque, reflective of critical torque, (44 ± 13 vs. 40 ± 15% pre-exercise MVC) were greater in the ACT trial compared to placebo (PL) when completing 60 maximum voluntary contractions (MVCs) of the knee extensors (both P < 0.05). Voluntary activation (VA; a marker of central fatigue) and potentiated twitch (pTw; a marker of peripheral fatigue) declined at a similar rate in both conditions (both P > 0.05). However, the decline in electromyography (EMG) amplitude, a marker of muscle activation, was attenuated in the ACT trial with EMG being greater compared to PL from 210 s onwards (P < 0.05). Study 2: Compared to PL, ACT ingestion increased end-test power, reflective of critical power (ACT: 297 ± 32 vs. PL: 288 ± 31 W, P < 0.001), and total work done (ACT: 66.4 ± 6.5 vs. PL: 65.4 ± 6.4 kJ, P < 0.05) without impacting Wˈ (ACT: 13.1 ± 2.9 vs. PL: 13.6 ± 2.4 kJ, P > 0.05) or the M-wave amplitude (P > 0.05) during a 3-min all-out cycling test. EMG declined throughout the 3-min protocol in both the PL and ACT conditions; however, the decline in EMG was attenuated in the ACT condition, with the EMG amplitude being greater compared to PL over the last 60 s of the test (P < 0.05). Study 3: Time-to-exhaustion (Tlim) during severe-intensity knee extensor exercise in the right leg was 19% shorter after completing prior severe-intensity knee extensor exercise to exhaustion in the left leg following placebo ingestion (Leg2PL) compared to no prior fatigue in the left leg (Leg2CON) (Leg2CON: 385 ± 104 vs. Leg2PL: 311 ± 92 s; P < 0.05). ACT ingestion did not improve Tlim in the left leg without prior contralateral fatigue (Leg1ACT) compared to the placebo condition (Leg1PL) (Leg1CON: 396 ± 105 vs. Leg1PL: 390 ± 106 vs. Leg1ACT: 402 ± 101 s; P < 0.05). Moreover, ACT ingestion did not improve Tlim in the right leg following prior contralateral fatigue in the left leg (Leg2ACT) compared to the placebo condition (Leg2PL) (Leg2ACT: 324 ± 85 vs. Leg2PL: 311 ± 92 s; P > 0.05). There were no changes in intramuscular phosphorous substrates and metabolites, ratings of perceived exertion or EMG amplitude after ACT ingestion compared to PL ingestion in the severe-intensity single-leg knee extensor exercise tests completed with or without prior contralateral fatigue. Study 4: Mean torque (IBP: 60 ± 12 vs. PL: 58 ± 14% of pre-exercise MVC) and end-test torque (IBP: 41 ± 16 vs. PL: 40 ± 15% of pre-exercise MVC) were not different between the IBP and PL conditions when completing 60 MVCs of the knee extensors (P > 0.05). Similarly, end-test power output (IBP: 292 ± 28 W vs. PL: 288 ± 31 W) and work done (IBP: 65.9 ± 5.9 kJ vs. PL: 65.4 ± 6.4 kJ) during the 3-min all-out cycling tests were not different between the IBP and PL conditions (all P > 0.05). Neuromuscular fatigue markers developed at a similar rate in both exercise tests in the PL and IBP conditions (all P > 0.05). In conclusion, acute consumption of ACT, but not IBP, increased muscle activation and critical torque (and power), and attenuated fatigue development during maximal-intensity knee extensor and cycle ergometry exercise. However, acute ACT ingestion did not influence Tlim during continuous severe-intensity knee-extension exercise completed with or without prior fatigue of the contralateral limb. The original findings from this work suggest that acute ACT ingestion, but not IBP ingestion, might have implications for improving performance during maximal-intensity, but possibly not severe-intensity constant work rate exercise with these ergogenic effects linked to an increase in muscle activation. These findings offer insights into the potential for non-specific COX inhibitors to influence performance and neuromuscular fatigue development during different forms of exercise.

Muscle fatigue is characterised by a transient (reversible with sufficient rest) decline in force generating capacity of the active musculature. This deterioration in force production capacity is associated with impaired neuromuscular function integrity, which includes both central and peripheral factors. An oxygen-deprived environment (hypoxia) accelerates and/or exacerbates development of muscle fatigue and ultimately hampers exercise tolerance. However, it is unclear how hypoxia of different severity during an initial exercise bout may influence recovery and performance of a subsequent exercise bout. The overarching aim of this thesis was to assess the impact of graded hypoxia during an initial intermittent exercise bout, on subsequent performance and neuromuscular and perceptual responses during closed-loop (i.e., pre-determined number of repeated cycling sprints; Study 1) and open-loop (i.e., exhaustive intermittent cycling bouts; Study 2) tasks. Results from Study 1 (Chapter 3) showed that single sprint performance was restored during the subsequent set of repeated sprints despite substantial impairments in muscle contractility (~45% decrease in quadriceps potentiated peak twitch from baseline). The restoration of sprint performance during the subsequent sprint set coincided with the recovery in exercise-related sensations and quadriceps muscle activation, which suggests that the central nervous system plays an important role in the recovery of sprint performance. However, the relatively brief repeated sprint (with a known endpoint) may have consciously or subconsciously influenced participants’ pacing strategy to “overcome” the impaired neuromuscular function for short duration, and increase power output. Therefore, Study 2 (Chapter 4) investigated the effects of graded hypoxia during an exhaustive intermittent cycling bout on subsequent performance and associated neuromuscular fatigue characteristics. It was observed that the number of efforts performed during the second bout was substantially lower compared to the first bout at sea-level, despite 30 min of passive recovery. This suggests that the residual effect of fatigue may only become apparent when 2 exercise is performed until exhaustion during an “open-loop” exercise task. Increasing hypoxia severity reduced the number of efforts completed during the initial cycling bout, but did not influence performance or neuromuscular fatigue characteristics during the second bout. The effects of prior high intensity intermittent exercise at graded hypoxia on subsequent performance and neuromuscular fatigue characteristics were essentially minimal. The residual effect of fatigue was task dependent. Specifically, when the subsequent exercise is brief, compensatory process associated with central factors (e.g. perceptual recovery) may aid in sustaining exercise performance. However, where exercise is prolonged, for instance till exhaustion, performance decrements associated with residual fatigue becomes evident. An important and consistent finding across studies was that using the fraction of inspired oxygen as a marker of “hypoxic dose” elicited large inter-individual differences in response to hypoxia, and consequently performance. As such, Chapter 5 proposed an individualised approach to implementing hypoxia, using SpO2 to FiO2 ratio as a marker of dose. Collectively, our findings showed that neuromuscular fatigue during high intensity intermittent exercise in hypoxia and normoxia were largely peripheral in nature. However, prior high intensity exercise in graded hypoxia does not influence performance and associated neuromuscular functions during subsequent exercise.

Trabalho apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Licenciado em Fisioterapia
Objectivo: O objectivo deste projecto foi o de reunir artigos que estudassem os efeitos agudos do alongamento na performance e força máxima, permitindo assim, uma revisão bibliográfica. Metodologia: Foi feita uma pesquisa em bases de dados com a MEDLINE/Pubmed research, b-on, e PEDro, para artigos do ano de 2000 até à actualidade, na língua inglesa. Os artigos tinham que ser todos experimentais, e tinham que respeitar os termos usados na pesquisa. Foram excluídos os artigos que fugissem minimamente ao tema. Também o uso dos nomes de autores foi usado, como forma de pesquisa, para poder ter mais estudos sobre este tema. Resultados: Todos os artigos selecionados tiveram resultados idênticos, com provas de que um alongamento estático e por técnica de facilitação neuromuscular proprioceptiva (PNF) diminuíam a performance muscular e também a força máxima. Já um alongamento dinâmico tinha como efeito um aumento da força e da performance muscular. Conclusões: Idealmente, deverão ser usados como forma de aquecimento para actividade fisica, os alongamentos dinâmicos, e evitar usar alongamentos estáticos(protocolos prolongados) ou por PNF. Objective: The objective of this study was to gather articles that would study the effects of stretching in muscle performance and in maximal voluntary force. Methods: A search in databases like MEDLINE/Pubmed research, b-on, and PEDro were made, for articles from the year 2000 to the present day, in the English language. The articles had to be experimental and all had to respect the terms used in the research. All who did not respect the study’s topic were excluded. Further on the research, names of authers were used, in order to bet access to more articles of the same subject. Results: All articles had identical results, proving that static ou PNF stretching could diminish performance and maximal voluntary force. As for dynamic stretch, improvements in performance and force are achieved. Conclution: Idealy, dynamic stretchs should be used as a warm up for physical activities, avoiding the use of static or PNF stretching.

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Introdução: O treinamento de salto é realizado habitualmente por atletas de voleibol. A fototerapia e a estimulação elétrica neuromuscular (EENM) são recursos eficazes na melhora da performance muscular. Porém, há pouca evidência que compare a utilização desses recursos no treinamento de salto em atletas de voleibol. Objetivo: Avaliar a adição da fototerapia e da estimulação elétrica ao treinamento de força muscular e salto em atletas de voleibol. Métodos: Trinta e seis atletas foram distribuídos aleatoriamente em 3 grupos (controle, fototerapia e EENM). Os atletas realizaram treinamento de força muscular e salto associado ou não a fototerapia e a EENM. Os desfechos avaliados foram: força muscular, habilidade de salto, efeito global percebido e frequência de salto na linha de base, e nos acompanhamentos de seis e oito semanas. Resultados: Houve diferença estatisticamente significante na força muscular do membro dominante com oito semanas de acompanhamento a favor do grupo fototerapia e EENM (diferença entre as médias = 1,7; IC 95% 1,1 a 2,4 e diferença entre as médias = 2,5; IC 95% 1,8 a 3,2 respectivamente) e diferença significante na força muscular do membro não dominante a favor do grupo fototerapia e EENM nos acompanhamentos de seis semanas (diferença entre as médias = 1,8; IC 95% 1,1 a 2,6 e diferença entre as médias = 2,6; IC 95% 1,7 a 3,6 respectivamente) e oito semanas (diferença entre as médias de 2,4; IC95% 1,7 a 3,1 e diferença entre as médias de 3,7; IC 95% 3 a 4,5 respectivamente). Os mesmos efeitos não foram observados nos demais desfechos. Conclusão: A fototerapia e a EENM promovem efeito benéfico no ganho de força muscular, porém estes efeitos não foram vistos nos desfechos de performance do salto.
Introduction: The jump training is usually done by volleyball players. Phototherapy and neuromuscular electrical stimulation (NMES) are effective resources in improving muscle performance. However, there is little evidence that compares the use of these resources in jump training in volleyball athletes. Objective: To evaluate the addition of phototherapy and electrical stimulation to the training of muscle strength and jump in volleyball athletes. Methods: Thirty-six athletes were randomly divided into 3 groups (control, phototherapy and EENM). The athletes performed strength training and associated jump or not phototherapy and EENM. The outcomes assessed were: muscular strength, jumping ability, overall effect and jump frequency at baseline and 6 and 8 weeks in follow-ups. Results: There were significant differences in muscle strength of the dominant limb with 8 weeks of follow-up in favor of phototherapy group and EENM (difference between means = 1.7, 95% CI 1.1 to 2.4 and difference between means = 2.5; 95% CI 1.8 to 3.2 respectively) and significant difference in muscle strength of the non-dominant limb in favor of phototherapy and EENM group in the 6- week follow-ups (difference between means = 1.8, 95 1.1 to 2.6% and difference between means = 2.6, 95% CI 1.7 to 3.6 respectively) and 8 weeks (difference between the average of 2.4, 95% CI 1.7 to 3 , and one difference between the average of 3.7, 95% CI 3 to 4.5, respectively). The same effects were not observed in other outcomes. Conclusion: Phototherapy and EENM promote beneficial effect on muscular strength gain, but these effects were not seen in the jump performance outcomes.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O objetivo do presente estudo foi investigar os efeitos da potenciação pós ativação (PAP) induzida por drop jumps no tempo até a exaustão a 115% da intensidade associada ao consumo máximo de oxigênio (("iV" ) ̇"O" _"2max" ) em ciclo ergômetro, em aspectos neuromusculares da fadiga (central e periférica) e sobre as vias metabólicas não oxidativas (capacidade anaeróbia, via glicolítica e dos fosfagênios). Para isso, o projeto foi dividido em dois estudos independentes. No Estudo A, 14 ciclistas recreacionais do sexo masculino (34 ± 4 anos) foram submetidos a 5 sessões de avaliações. Na primeira sessão realizaram teste incremental até exaustão (TInc), na segunda e terceira avaliações realizaram familiarização ao esforço supramáximo a 115% da ("iV" ) ̇"O" _"2max" , enquanto que na quarta e quinta sessões os participantes realizaram de maneira randomizada o esforço supramáximo a 115% da ("iV" ) ̇"O" _"2max" com e sem PAP (controle). Como esforço indutor da PAP, foram realizados 5 drop jumps (15s de intervalo entre eles) antes do esforço supramáximo. Nas sessões 4 e 5, a fadiga neuromuscular foi avaliada por meio de contrações voluntárias máximas (CVM) de extensão do joelho e estimulação elétrica periférica (PNS) realizadas antes e após o esforço supramáximo. Além disso, a eletromiografia de superfície foi realizada durante o esforço supramáximo para mensuração da roots mean square (EMGRMS) e a frequência mediana (EMGFM) e analisadas de forma estratificada a cada 25% de tempo total de esforço (0-25%, 25-50%, 50-75% e 75-100%). No Estudo B, 16 ciclistas recreacionais do sexo masculino (33 ± 6 anos) realizaram desenho experimental semelhante ao estudo A, entretanto na quarta e quinta sessões, as contribuições dos sistemas metabólicos foram mensuradas pelo componente rápido do excesso de consumo de oxigênio pós exercício (EPOC) (via dos fosfagênios) e pelo delta de lactato (via glicolítica), assumindo a soma das contribuições dessas vias como capacidade anaeróbia (AC[La-]+EPOCrápido), além disso a capacidade anaeróbia também foi mensurada pelo déficit máximo de oxigênio acumulado. Como resultados, no estudo A foi verificado uma melhora do significativa desempenho no esforço supramáximo após a realização da PAP (p=0,02; Δ%=+9,85%). Ambas condições (controle e PAP) apresentaram quedas significativas na força pico medidas durante a CVM e na força evocada pelo estímulo elétrico duplo na musculatura em repouso (p<0,01 e p<0,01, respectivamente) quando comparado o momento pré e pós esforço, indicando uma fadiga periférica causada pelo esforço. Entretanto não houve interação entre as condições (F=4,19; p=0,06 e F=3,03; p=0,09, respectivamente). A EMGRMS e a EMGFM do último quarto de esforço (75-100%) foi significativamente maior que os momentos 0-25%, 25-50%, 50-75%, para ambas as condições (p<0,02), entretanto não houve interação entre grupos (p<0,05). No Estudo B o desempenho no esforço supramáximo foi significativamente maior na condição PAP (p=0,05; Δ%=+7,44%). A contribuição glicolítica e a capacidade anaeróbia mensurada pelo AC[La-]+EPOCrápido foram maiores após a PAP (p=0,002; Δ%= +9,09% e p=0,04; Δ%= +7,75%, respectivamente), entretanto, a contribuição dos fosfagênios não apresentou diferenças significativas entre condições (p=0,35). Portanto, a PAP foi efetiva em melhorar o desempenho em um esforço supramáximo em ciclo ergômetro, tendo sua melhora acompanhada por um aumento da participação glicolítica e da capacidade anaeróbia, além de causar uma “preservação” do aparato neuromuscular durante o esforço para o vasto lateral e o glúteo máximo.
The aim of the present study was investigating the effects of post activation potentiation (PAP) induced by drop jumps in performance during a supramaximal effort at 115% of the intensity associated with maximal oxygen uptake (iV̇ O2max) on a cycle ergometer, also investigating the influence of PAP on neuromuscular fatigue (central and peripheral) and, on the non-oxidative metabolic pathways (anaerobic capacity, glycolytic pathway and phosphagen). Therefore, the project was divided in two independent studies. In Study A, 14 recreational male cyclists (34 ± 4 years) underwent 5 sessions of evaluations, in the first session they performed a graded exercise test (GXT), in the second and third evaluations they performed familiarization to the supramaximal effort to 115% of the iV̇ O2max. In the fourth and fifth sessions, the participants randomly performed the supramaximal effort at 115% of the iV̇ O2max with PAP and without PAP (control). To induce PAP, the volunteers performed 5 drop jumps (15s interval between them) 2 minutes before the supramaximal effort. In sessions 4 and 5, neuromuscular fatigue was assessed by maximal voluntary contractions (CVM) of knee extension with peripheral electrical stimulation (SNP) performed before and after the supramaximal effort. In addition, surface electromyography was performed during the supramaximal effort to measure roots mean square (EMGRMS) and the median frequency (EMGFM) for every 25% of total effort time (0-25%, 25-50%, 50-75% and 75-100% %). In Study B, 14 male recreational cyclists (33 ± 6 years) performed experimental design similar to study A, however in the fourth and fifth session, the contributions of the non-oxydative metabolic systems were measured by the fast component of the excess post-exercise oxygen consumption (EPOC) and the lactate delta (glycolytic pathway), assuming the sum of the contributions of these pathways as anaerobic capacity (AC[La -] + EPOCfast). In addition, the anaerobic capacity was also measured by the maximum accumulated oxygen deficit (MAOD). In study A, an improvement in the supramaximal effort was observed after PAP (p=0.02, Δ%=+9.85%). Both conditions (control and PAP) showed significant decrease in the peak force measured during the CVM and in the force evoked by the double electric stimulus in the resting muscles (p<0.01 and p <0.01, respectively) when compared to the pre and post moments, indicating peripheral fatigue caused by the supramaximal effort. However, ere was no interaction between the conditions (F=4.19, p=0.06 and F=3.03, p=0.09, respectively). The EMGRMS and EMGFM of the last quarter of effort (75- 100%) was significantly higher than the 0-25%, 25-50%, 50-75%, moments for both conditions (p <0.02), however there was no interaction between groups (p<0.05). In Study B, performance on supramaximal effort was significantly higher in the PAP condition (p=0.05, Δ%=+7.44%). The glycolytic contribution and the anaerobic capacity measured by AC[La -] + EPOCfast was higher after PAP (p=0,002; Δ%= +9,09% e p=0,04; Δ%= +7,75%, respectively), however, the contribution of the phosphagen pathway did not show significant differences between conditions (p = 0.35). Therefore, the PAP was effective in improving the performance in a supramáximo effort in cycle ergometer, having its improvement accompanied by an increase in the glycolytic participation and in anaerobic capacity, in addition to causing a "preservation" of the neuromuscular apparatus during the effort for the vastus lateralis and gluteus maximus
FAPESP: 2016/17836-2

Supporters of a nutritional supplement, β-Hydroxy-β-Methylbutyrate (HMB) supplementation, claim that it will increase the muscular strength gains and lean muscle mass gains seen during a resistance training program. It has been suggested that HMB supplementation does this by preventing muscle damage or by regenerating damaged muscle cell membranes. However, no research has evaluated the effect of HMB supplementation on low frequency fatigue. Therefore, the purpose of this study was to determine if three weeks of HMB supplementation could attenuate the effects of low frequency fatigue caused by eccentric muscle contractions of the tibialis anterior muscle. A total of 33 healthy recreationally active subjects (18 males, 15 females; 23.2 ± 4.3 yr) were recruited for this study. All subjects preformed 4 sets of 25 eccentric contractions of the tibialis anterior muscle through a range of motion of 30 degrees. Recovery measures were taken for 20 minutes after the fatigue protocol and at 48 and 96 hours of recovery. The recovery measures included: Maximum voluntary contraction peak torque, 10 Hz peak torque, 50 Hz peak torque, 10/50 Hz peak torque ratio, and EMG measurements. Each subject served as their own control and limbs were randomly assigned to pre-supplement or post-supplement limbs. Following the pre-supplement fatigue protocol and recovery measures each subject completed three weeks of 3g/day HMB supplementation. After the supplementation period the post-supplement fatigue protocol was completed and recovery measures were taken. The 10 Hz peak torque and the 10/50 Hz torque ratio in the pre-supplement limb was still significantly reduced at the 96-hour recovery measurement time, indicating that it was still showing low frequency muscle fatigue at this time. Furthermore, the post-supplement limb, recovered from the fatigue protocol faster, and did not show any signs of low frequency muscle fatigue at the 48-hour recovery measurement time. In addition the pre-supplement limb had significant maximum voluntary contraction torque deficit at the 48-hour recovery measurement time and the post-supplement limb showed no significant deficits. The main findings of this study were that three weeks of HMB supplementation attenuated low frequency fatigue and maximum voluntary contraction torque reduction after an eccentric fatigue protocol.

La pratique d’exercices intenses répétés, entrecoupés de faibles temps de récupération, est susceptible d’engendrer une altération de l’homéostasie et une diminution de la performance chez les sportifs soumis à ce type de contraintes. Dans ce contexte, l’optimisation des processus de récupération est une possibilité forte d’amélioration de la performance et de sa reproduction. Une des principales limites au maintien de la performance de type haute intensité, répété à court terme, est attribuée à la fatigue périphérique, inhérente à l’ensemble des mécanismes de l’excitabilité et de la contraction du muscle squelettique. Cette fatigue périphérique engendre une inadéquation entre les apports et les besoins cellulaires, en oxygène et en nutriments, ainsi qu’une incapacité à éliminer et/ou recycler les produits métaboliques issus de la contraction musculaire. Afin de limiter ces effets, l’augmentation du flux sanguin lors de l’exercice et de la récupération apparaît indispensable au bon rétablissement de l’état d’équilibre de l’organisme et au maintien de la performance sportive. A ce titre, l’électrostimulation neuromusculaire semble être un mode de récupération théoriquement efficace pour augmenter le flux sanguin. Cette présente thèse, comprenant trois études, visait à connaître précisément les effets de l’électrostimulation neuromusculaire - par l’utilisation d’un nouvel appareil issu du domaine médicale - sur la cinétique de récupération de marqueurs de performance, de marqueurs physiologiques et de perception, dans le contexte d’exercices intenses, répétés à court terme. Nous avons émis l’hypothèse qu’une stimulation efficace, induisant une augmentation du flux sanguin, permettrait d’optimiser la récupération à court terme, entre deux exercices de haute intensité. Ces résultats devraient permettre d’optimiser, dans le futur, les stratégies de récupération mises en place après un exercice intense, répété dans de brefs délais
The practice of intense and repeated exercises, interrupted with short recovery times, may induce alterations in homeostasis and a decrease of the performance for athletes who are subject to this type of constraints. In this context, the optimization of the recovery processes is a strong possibility to improve performance and the maintain of it all along the competitive period. One of the main limits in the preservation of performance in type high-intensity, repeated at small interval of time, is attributed to the peripheral fatigue, inherent to all the mechanisms implied in the skeletal muscle excitability and contraction. This peripheral fatigue induces an inadequacy between the contributions and the cellular needs of oxygen and nutrients, and also a disability for disposal or recycling the metabolic by-products stemming from the muscular contraction. In order to limit these effects, the increase in blood flow during exercise and recovery seems essential for the good restoring of the state of physiological balance for the body and the preservation of sport performance. Therefore, the neuromuscular electrical stimulation seems to be, in theory, an effective recovery mode to improve the blood flow. This present thesis, comprising three studies, aimed to know precisely the effects of the neuromuscular electrical stimulation - by the use of a new device stemming from the medical field - on the kinetics of recovery of performance, physiological and perceptual markers, in the context of intense exercises repeated in the short terms. We hypothesized that an effective stimulation, increasing the blood flow would allow to optimize short-term recovery between two high-intensity exercises. These results should contribute to optimize, in the future, the strategies of recovery organized after an intense exercise

The purpose of this dissertation is to better understand the role of repeated-sprint ability (RSA) and resulting fatigue in cyclists; how it relates to measures of aerobic power and strength and power performance indices- due to the nature of cycling competitions and the necessity of RSA for success. The first part of this dissertation attempted to elucidate the relationship between RSA and aerobic power and strength/ power measures in competitive cyclists. The purpose was to potentially illustrate the importance of the inclusion of strength and power training in the training regimen of cyclists. The findings showed several statistically significant relationships between variables of RSA and aerobic power or the isometric squat test. The second part of the dissertation examined the effects of fatigue induced from the acute bout of repeat sprint exercise on strength and power measures in three different recovery periods. It is commonplace for cyclists to have several heats in one day of racing. Examining the effects of fatigue on strength measures such as peak force and rate of force development could begin to delineate how an individual experiences fatigue based on their own characteristics, enabling them to design a training program to address these strengths/ weaknesses to optimize performance and decrease fatigue. The results from a repeated measures analysis of variance found no statistically significant effect on PF or RFD. Additional comparisons showed moderate effects of fatigue on RFD throughout the three post-RSE trials. There was also a moderate correlation between the RSE fatigue % decrement score and the isometric RFD fatigue % decrement score. What we may conclude from this dissertation is that fatigue has various causes and can vary with an individuals’ unique physiology and how they respond to performance variables on any specific day can vary. Development of increased strength and subsequent power, or “explosive strength”, may have advantages in competitive cycling. Coupling proper strength and power training with an aerobic training regimen, may greatly benefit the athlete by increasing their peak power output, economy of movement, delaying fatigue, improving anaerobic capacity, and overall enhancing their maximal speed.

El control neuromuscular ha estat descrit com un important factor per a l'èxit en el rendiment esportiu. De la mateixa manera, també s'ha identificat com a clau en la prevenció i readaptació de les lesions esportives. El principal objectiu d'aquesta tesi doctoral és avaluar l'eficàcia de diferents tipus d'entrenament neuromuscular en esportistes.
S'ha utilitzat una mostra de 81 esportistes sans entre els diferents estudis que s'hi presenten. Les diferents avaluacions realitzades han registrat els següents ítems: dolor (escala visual analògica), incidència de lesions esportives, estabilitat postural estàtica i dinàmica (estabilometria i salt unipodal) i força explosiva de l'extremitat inferior (salt amb contramoviment). Els dos mètodes d'entrenament neuromuscular utilitzats són l'anomenat TRAL (Teràpia Reequilibradora de l'Aparell Locomotor) i les VCS (vibracions de cos sencer).
La primera part d'aquesta tesi (Estudis I i II) va tenir l'objectiu de valorar l'eficàcia del mètode TRAL. Aquest va produir una reducció significant del dolor de turmell independentment del gènere registrat, mentre que en el cas del dolor de genoll només hi van haver diferències en les noies estudiades. Un dels altres efectes registrats importants a destacar va ser la reducció significant de l'àrea de desviació del centre de pressions en el cas de les noies, el que representa una millora de l'estabilitat postural. Aquesta dada també va ser positiva en una de les proves registrades en el grup de nois.
La segona part d'aquest treball (Estudi III) es va centrar en donar fiabilitat a una bateria de tests d'equilibri mesurats amb un estabilòmetre, tenint com a objectiu valorar l'estabilitat estàtica i dinàmica de l'extremitat inferior. Es va obtenir una correlació de bona a excel·lent en totes les variables de la millor amplitud promig en el test unipodal d'ulls oberts i tancats. Aquests resultats suggereixen una bona fiabilitat per a la distinció entre grups de subjectes. En el cas del test més dinàmic i proper a la realitat de l'esportista, el salt unipodal, la correlació va ser baixa.
Com a continuació d'aquesta segona part, l'estudi IV va comparar de forma transversal les diferències de l'estabilitat postural estàtica i dinàmica segons sexe i cama dominant. El test d'equilibri unipodal d'ulls oberts no va mostrar diferències significatives en la desviació del centre de pressions entre homes i dones. D'altra banda, el sexe femení va mostrar un major equilibri en els tests més dinàmics (UT i S) en comparació amb el sexe masculí. En relació a les diferències entre cama dominant - no dominant, només es van trobar diferències significatives en les dones en la recepció del salt unipodal, mostrant-se un millor control quan la recepció s'efectuava amb la cama dominant.
La següent línia de treball es va iniciar amb l'estudi V, que va consistir en una revisió sistemàtica sobre els efectes de l'entrenament vibratori sobre el rendiment esportiu en persones físicament actives. Els resultats van mostrar una gran heterogeneïtat clínica i una baixa qualitat metodològica dels treballs analitzats fins la data cercada. Malgrat no poder extreure conclusions clares, existeix una tendència a la millora de la força explosiva. També podem establir un rang segur dels paràmetres d'aplicació de vibracions mecàniques sobre la població d'estudi. Aquest es troba entre 1,7-11mm d'amplitud i entre 20-44 Hz de freqüència, aplicant-se tant en exercicis estàtics com dinàmics i fins a un màxim de 18 minuts de durada per sessió.
Per últim, es va realitzar un assaig clínic controlat aleatori (Estudi VI) amb l'objectiu de valorar l'eficàcia de l'entrenament mitjançant vibracions de cos sencer sobre la força explosiva i el control postural en joves jugadores de bàsquet. Els resultats van mostrar un increment significatiu del salt amb contramoviment, del salt unipodal i de l'equilibri amb ulls tancats a les 8 i 15 setmanes d'entrenament en el grup experimental. És destacable el fet que no es trobessin diferències significatives entre els tests realitzats a les 8 i les 15 setmanes d'entrenament en cap de les variables. D'altra banda, el grup control no va experimentar canvis respecte les valoracions preintervenció. Amb aquests resultats podem afirmar que l'entrenament vibratori possibilita la millora dels paràmetres analitzats, repercutint favorablement en el rendiment esportiu i, també, de forma indirecta, en la prevenció de lesions en esportistes d'alt risc.
A forma de síntesi, els estudis d'aquesta tesi emfatitzen la importància del control neuromuscular sobre el rendiment i prevenció de lesions esportives. És necessari destacar la importància de continuar investigant sobre noves eines que mesurin els paràmetres associats al control neuromuscular, així com seguir estudiant l'eficàcia dels diferents mètodes d'entrenament neuromuscular per a la seva optimització.
El control neuromuscular ha sido descrito como un importante factor para el éxito en el rendimiento deportivo. Del mismo modo, también se ha identificado como clave en la prevención y readaptación de las lesiones deportivas. El principal objetivo de esta tesis doctoral ha sido evaluar la eficacia de diferentes tipos de entrenamiento neuromuscular en deportistas.
Se ha utilizado una muestra de 81 deportistas sanos entre los diferentes estudios que se presentan. Las diferentes evaluaciones realizadas han registrado los siguientes ítems: dolor (escala visual analógica), incidencia de lesiones deportivas, estabilidad postural estática y dinámica (estabilometría y salto unipodal) y fuerza explosiva de la extremidad inferior (salto con contramovimiento). Los métodos de entrenamiento neuromuscular utilizados fueron el llamado TRAL (Terapia reequilibradora del Aparato Locomotor) y las VCE (vibraciones de cuerpo entero).
La primera parte de esta tesis (Estudios I y II) tuvo el objetivo de valorar la eficacia del método TRAL. Este produjo una reducción significativa del dolor de tobillo independientemente del género registrado, mientras que en el caso del dolor de rodilla sólo hubo diferencias en las chicas estudiadas. Otro de los efectos registrados importantes a destacar fue la reducción significativa del área de desviación del centro de presiones en el caso de las chicas, lo que representa una mejora de la estabilidad postural. Este dato también fue positivo en una de las pruebas de equilibrio registradas en el grupo de chicos.
La segunda parte de este trabajo (Estudio III) se centró en dar fiabilidad a una batería de tests de equilibrio medidos con un estabilómetro, teniendo como objetivo valorar la estabilidad estática y dinámica de la extremidad inferior. Se obtuvo una correlación de buena a excelente en todas las variables de la mejor amplitud media en el test unipodal de ojos abiertos y cerrados. Estos resultados sugieren una buena fiabilidad para la distinción entre grupos de sujetos. En el caso del test más dinámico y cercano a la realidad del deportista, el salto unipodal, la correlación fue baja.
Como continuación de esta segunda parte, el estudio IV comparó de forma transversal las diferencias de la estabilidad postural estática y dinámica según sexo y pierna dominante. El test de equilibrio unipodal de ojos abiertos no mostró diferencias significativas en la desviación del centro de presiones entre hombres y mujeres. Por otro lado, el sexo femenino mostró un mayor equilibrio en los tests más dinámicos (UT y S) en comparación con el sexo masculino. En relación a las diferencias entre pierna dominante - no dominante, sólo se encontraron diferencias significativas en las mujeres en la recepción del salto unipodal, mostrándose un mejor control cuando la recepción se efectuaba con la pierna dominante.
La siguiente línea de trabajo se inició con el estudio V, que consistió en una revisión sistemática sobre los efectos del entrenamiento vibratorio sobre el rendimiento deportivo en personas físicamente activas. Los resultados mostraron una gran heterogeneidad clínica y una baja calidad metodológica de los trabajos analizados hasta la fecha buscada. A pesar de no poder extraer conclusiones claras, existe una tendencia a la mejora de la fuerza explosiva. También podemos establecer un rango seguro de los parámetros de aplicación de vibraciones mecánicas sobre la población de estudio. Este se encuentra entre 1,7-11mm de amplitud y entre 20-44 Hz de frecuencia, aplicándose tanto en ejercicios estáticos como dinámicos y hasta un máximo de 18 minutos de duración.
Por último, se realizó un ensayo clínico controlado aleatorio (Estudio VI) con el objetivo de valorar la eficacia del entrenamiento mediante vibraciones de cuerpo entero sobre la fuerza explosiva y el control postural en jóvenes jugadoras de baloncesto. Los resultados mostraron un incremento significativo del salto con contramovimiento, del salto unipodal y del equilibrio con ojos cerrados a las 8 y 15 semanas de entrenamiento en el grupo experimental. Es destacable el hecho de que no se encontraran diferencias significativas entre los tests realizados a las 8 y las 15 semanas de entrenamiento en ninguna de las variables. Por otra parte, el grupo control no experimentó cambios respecto a las valoraciones preintervención. Con estos resultados podemos afirmar que el entrenamiento vibratorio posibilita la mejora de los parámetros analizados, repercutiendo favorablemente en el rendimiento deportivo y, también, de forma indirecta, en la prevención de lesiones en deportistas de alto riesgo.
En forma de síntesis, los estudios de esta tesis enfatizan la importancia del control neuromuscular sobre el rendimiento y prevención de lesiones deportivas. Es necesario destacar la importancia de continuar investigando sobre nuevas herramientas que midan los parámetros asociados al control neuromuscular, así como seguir estudiando la eficacia de los diferentes métodos de entrenamiento neuromuscular para su optimización.
Neuromuscular control is believed to be an important factor for success in athletic performance. Similarly, it has also been identified as a key to prevention and rehabilitation of sports injuries. The main objective of this thesis is to evaluate the effectiveness of different types of neuromuscular training in athletes.
A total of 81 healthy athletes were used for the purpose of the study. The evaluations performed have resulted in the following items: pain (visual analogue scale), incidence of sports injuries, static and dynamic postural stability (stabilometry and one-leg hop test) and explosive strength of the lower extremity (countermovement jump). Neuromuscular training methods used were TRAL (Locomotive rebalancing therapy) and WBV (whole body vibration).
The first part of this thesis (Studies I and II) aims to assess the efficacy of TRAL. The training period showed a significant reduction of ankle pain recorded regardless of gender, whereas in the case of knee pain only differences in the girls studied were found. Another important effect to highlight that contributes to an improvement of stability in body position in women is the significant reduction of movements of the centre of pressure, while there was only a significant reduction in one of the men tests.
The aim in the second part (Study III) is to assess the static and dynamic stability of the lower extremities focusing on battery of tests reliability measured with a stabilometer. Correlation obtained in single leg stance test of open and closed eyes was found in the range between good to excellent, in all variables of t he best average amplitude. These results suggest a good reliability for the distinction between subject groups. Regarding a more dynamic and closer to athlete's reality test, the one-leg hop test, poor correlation was obtained.
Continuing in the second part, study IV compares differences between static and dynamic position stability, by sex and leg dominance. The one leg stance with open eyes test showed no significant difference in the deviation of center of pressure between men and women. Moreover, females showed more balance in higher dynamics tests (UT and S) compared with males. The differences regarding dominant - non dominant leg, were found only in girls in receiving one leg jump, showing a better control where the reception took place with the dominant leg.
The next topic begins with study V, which consists of a systematic review on the effects of vibration training in physically active people. The results demonstrate a high clinical --heterogeneity and low methodological quality of previous studies performed prior to the date of our study. Even if we cannot provide a specific result, there is a tendency to improve explosive strength. Also, we can certainly establish a safe range of parameters for vibration training to be applied on a physically active population. This range goes from 1.7-11mm amplitude, 20-44 Hz frequency, both in static and dynamic exercises, and up to 18 minutes working with vibration.
In the last topic, we conduct a randomized controlled trial (Study VI) aimed to assess the effectiveness of whole body vibration training on explosive strength and postural control in young basketball players. The results showed a significant increase in countermovement jump, one-leg hop test and balance with closed eyes at 8 and 15 weeks of training with the experimental group. It is noteworthy that no significant differences were found between tests performed at 8 and 15 weeks of training in any of the variables. Moreover, the control group experienced no changes from pre-intervention assessments. Based on these results we can state that vibration training enables the improvement of the analyzed parameters, impacting positively on athletic performance, and indirectly prevents injuries in high-risk athletes.
In conclusion, this thesis emphasizes the importance of neuromuscular control on sports performance and prevention of injuries. It is necessary to stress the importance of continuing the research on new tools to measure parameters associated with neuromuscular control, and further studying the effectiveness of different methods of neuromuscular training for its optimization.

Experiment 1: To determine if the magnitude of improvements in athletic performance and the mechanisms driving these adaptations differ in relatively weak individuals exposed to either ballistic power training or heavy strength training. Experiment 2: To determine if the magnitude of performance improvements and the mechanisms driving adaptation to ballistic power training differ between strong and weak individuals. Experiment 3: To determine if ballistic power training and heavy strength training result in specific changes to power absorption (i.e. power generated during the eccentric phase) and production (i.e. power generated during the concentric phase) and if so, whether these changes are influenced by the individual‟s strength level. An additional purpose was to assess whether potential training induced changes in power absorption and production are influenced by alterations to factors commonly associated with SSC function (i.e. rate and magnitude of stretch, time of movement).

The main concern of this thesis was to evaluate the effects of strenuous eccentric exercise on specific indices of neuromuscular and sensorimotor performance. The effects and symptoms of exercise-induced muscle damage (EIMD) have been very well documented in adult populations. They include impairments in muscle function (isometric and dynamic strength, power and rate of force development and flexibility), an increase in the release of muscle proteins (e.g. creatine kinase), delayed onset muscle soreness and an increase in perceived exertion. However, very little research has focussed on the effects of EIMD on electromechanical delay and sensorimotor performance. Even less attention has focussed on the effects of strenuous eccentric exercise on children populations. To date, only four studies have investigated the effects of EIMD in children, although these studies did not assess the effects of EIMD on sensorimotor performance. This thesis comprises six chapters: • Chapter 1: Introduction • Chapter 2: Review of Literature • Chapter 3: Reproducibility and Single Measurement Reliability of Indices of Neuromuscular and Sensorimotor Performance of the Knee Flexors in Adults and Children. • Chapter 4: Evaluation of the Effects of two bouts of strenuous isokinetic eccentric exercise on Sensorimotor and Neuromuscular Performance of the knee flexors in Men and Women. • Chapter 5: Evaluation of the effects of a bout of strenuous eccentric exercise on sensorimotor and neuromuscular performance of the knee flexors in young athletes. • Chapter 6: Further thoughts, conclusions and limitations. Chapter 3 examined the single-measurement reliability and reproducibility of selected indices of neuromuscular and sensorimotor performance that were deployed in the subsequent chapters of this thesis in adults and children. The results demonstrated no statistically significant differences (P > 0.05) between groups (males, females, boys and girls), which suggested that considerations regarding the testing protocols could be made on the same basis for all the selected groups. Similarly, no significant differences were observed between legs (preferred, non-preferred) in any of the involved groups. Furthermore, the findings demonstrated that single-trial protocols are not powerful enough for the accurate discrimination of intra-session differences in performance capabilities especially during intra-individual assessments and moreover are insufficient for the correct interpretation of neuromuscular and sensorimotor performance between days. Chapter 4 assessed the effects of two bouts of exercise-induced muscle damage on neuromuscular and sensorimotor performance of the knee flexors of both legs in males and females. The eccentric exercise protocols were associated with impaired peak force, elevated soreness, decreased passive flexibility, prolonged electromechanical delay and preserved sensorimotor performance. However, no significant differences between men and women were observed. Interestingly, the prolonged electromechanical delay and the preserved sensorimotor performance were the novel and most important findings of this study and were contrary to previous observations. Finally chapter 5 assessed the effects of a strenuous eccentric exercise protocol on neuromuscular and sensorimotor performance of the knee flexors of both legs in boys and girls (aged 11-14 years) who were members of the Exeter Tennis Centre. The eccentric exercise protocol was associated with impaired peak force, elevated soreness, decreased passive flexibility, and preserved electromechanical delay and sensorimotor performance. Interestingly, all impaired indices of muscle function returned to baseline 72 hours after the damaging protocol. Moreover, there were no significant sex differences. Further analysis revealed that boys and girls experienced milder symptoms of muscle damage than men and women, with the adult participants demonstrating higher levels of peak force decrease and of delayed onset muscle soreness.

Introduction: Hypermobility syndrome (HMS) is a common cause of morbidity in children, with the knee most frequently affected by its symptoms. Impaired joint proprioception has been reported in adults with HMS. Muscle weakness, problems with school activities and abnormal gait patterns have been observed in children with this condition. It has also been suggested that activities of daily living and physical and sporting activities may be limited in children with HMS due to pain. To date, the factors associated with HMS in children have not been well reported. The relationships between impairments, function and quality of life (QoL) have not been investigated in children with this condition. The purpose of this study was to identify the range of neuromuscular performance, functional range of motion (ROM) and QoL indices, and investigate the relationships between these features in children with HMS. A purpose-built motorised device was developed and validated for the assessment of knee joint proprioception as an integral part of the research programme. The test-retest repeatability of various outcome measures used for the present study was also investigated in healthy children and those with HMS. Methods: A cross-sectional study was conducted. Twenty nine children with HMS and 37 healthy children (aged 8 – 15 years) were investigated for neuromuscular indices, functional ROM and QoL. Knee joint kinaesthesia (JK) and position sense (JPS) were examined using a motorised device, muscle torque was tested with a digital myometer, passive ROM was measured with a universal goniometer and functional ROM was assessed using the VICON camera system. Pain intensity and QoL were measured using the Coloured Analogue Scale and the Paediatric Quality of life Inventory respectively. Mann-Whitney U tests and independent t-tests were performed to determine the differences between the two groups. The relationships between pain and each of the following: neuromuscular impairments, functional ROM and QoL were examined in children with HMS. The correlation between Beighton scores and each outcome was also evaluated in children with HMS. Results: Knee JK and JPS were significantly poorer (both p < 0.001) in children with HMS compared with the controls. Significantly reduced (p < 0.001) knee muscle torque was also observed in children with HMS. Pain intensity and passive knee ROM were significantly higher (both p < 0.001) in children with HMS. They also demonstrated significantly increased knee extension, reduced knee flexion in loading response and during maximal knee flexion of walking (all p <0.001). Moreover, the overall QoL perception and all the domains were significantly poorer (p range < 0.001 to 0.008) in children with HMS than the controls. No relationship (r range = -0.065 to 0.271; p range = 0.106 to 0.985) was found between pain, neuromuscular impairments and functional ROM in children with HMS. However, a significantly strong negative relationship (r = -0.65; p = <0.001) was established between pain and QoL in children with HMS. In addition, no relationship (r range = -0.014 to 0.315; p range = 0.112 to 0.895) was observed between Beighton scores and neuromuscular impairments, functional ROM and QoL in children with HMS. Conclusions: Children with HMS, compared with their healthy counterparts had knee joint proprioception and knee muscle torque deficits, increased passive knee ROM and pain intensity. Abnormal walking patterns (increased knee extension, reduced knee flexion in both mid stance and maximum knee flexion in swing phase during walking) were also found in children with HMS. They also presented with poorer QoL in comparison with the controls. Clinicians are to be aware of these identified features and should develop appropriate treatment intervention programmes for children with this condition.

Rehabilitation following Anterior Cruciate Ligament (ACL) Reconstruction (ACLR) benefits most patients electing ACLR surgery. Contemporary practice offers limited adaptation of the service to the needs of individual patients. This thesis focuses on a Randomised Control Trial (RCT) that evaluated the effects of a novel formulation of patient-centred musculoskeletal rehabilitation involving the Performance Profiling Technique (Butler and Hardy, 1992). Performance Profile Management (PPM), a programme of rehabilitation, was adapted to incorporate patient-physiotherapist negotiation and agreement on decisions for subsequent rehabilitation and treatment strategies. Therefore, the primary aim of the research was primarily to assess the efficacy of individually-tailored, self-managed rehabilitative care (PPM) in comparison to contemporary (CON) clinical practice. The latter would facilitate an understanding of patient needs and verify the circumstances in which rehabilitation might be enhanced by allowing individuals to play a key role in designing their treatment and recovery. A secondary clinical aim was to evaluate the strength of relationships amongst Patient-Based Outcome Measures (P-BOMs) and Clinician-Based Outcome Measures (C-BOMs). Currently, it is unknown which combination of outcome measures (P-BOMs or C-BOMs) delivers an optimum global assessment of functional and physical performance capabilities during patients’ post-surgical rehabilitation. A clinically-relevant and significant association amongst P-BOMs and C-BOMs might indicate correct scaling of patients’ own capability perceptions with those measured using objective assessment methods (C-BOMs) and endorse the utility for the clinical use of P-BOMs.

Whole-body vibration (WBV) may positively influence performance acutely through the potentiation of the muscle’s series elastic components and neuromuscular mechanisms. The purpose of this investigation was to examine the acute effects of WBV on sprint performance in NCAA Division I collegiate male sprinters and jumpers. Twenty-one athletes (n=21) completed a control or WBV protocol (30 seconds, 50 Hz, low amplitude ~3mm) one minute before a 30 m flying sprint. Each athlete participated in three separate trials using randomized treatment sessions (1 treatment per session) over 12 weeks of preparation training prior to the indoor season. The control condition consisted of no vibration, while treatment 1 (T1) and treatment 1 repeated (T1-R) incorporated vibration. The vibration-sprint protocol was repeated after a five minute rest period following the first sprint (test-re-test ICC≥0.81). The sprint consisted of a 15 m run-in from a standing start and a 30 m flying sprint with a total distance of 45 m. A two-way factorial ANOVA with repeated measures (p ≤ 0.05) was used to compare treatments. Statistics showed no differences between the treatments at all distances (average sprint time of control vs. T1, control vs. T1-R, and T1 vs. T1-R). The results of this study indicate that WBV at 50 Hz and low amplitude has no potentiation effect on sprint times (15, 30, 45, or 30 m fly). Further research is needed to determine if different WBV protocols may elicit enhanced results in 30 m flying sprint performance. The present WBV protocol does not appear to have practical acute value for sprinting.

Introduction: It has been proposed that inadequate rest intervals may contribute to decreased performance of activities. However, previous research has not investigated the effect of rest interval on performance of the Star Excursion Balance Test (SEBT) in individuals with and without chronic ankle instability. Objective: To determine whether rest interval affects performance of the SEBT associated with chronic ankle instability (CAI) and whether neuromuscular function, postural control or biomechanics can be associated factors which may help discriminate between healthy individuals and those with CAI during the SEBT. Design: 2-group counterbalanced study. Participants: Participants included 24 individuals with a history of at least one ankle sprain in the past year and at least 2 episodes of giving way in the past 6 month prior to study enrollment, and 24 individuals with no history of ankle sprain or instability in their lifetime. Methods: Subjects completed 3 trials in each of the 3 reach directions (anteromedial, medial, posteromedial) in random order. A total of three visits were required in order to complete the 3 rest intervals (10, 20, 40 seconds). Normalized maximum reach distance, electromyographic (EMG) activation of tibialis anterior, peroneus longus, and medial gastrocnemius muscles, multiplanar motion of the lower extremity, coupling angles (CA) of lower extremity segments and maximum lateral center of pressure velocity were calculated and compared between groups in each direction for each rest interval. Results: Rest interval did not influence differences of reach distance, EMG ankle muscle activation, kinematics and center of pressure velocity between healthy individuals and those with CAI during the SEBT. However, the rest interval of 20 seconds demonstrated differences in CAs of tibial internal rotation/dorsiflexion (TIR/DF) and tibial internal rotation/eversion (TIR/EV) between healthy individuals and those with CAI during the SEBT. Overall, reach distance, mean amplitude of EMG ankle muscles, kinematics and joint CAs were different between healthy individuals and those with CAI during the SEBT regardless of rest interval. Discussion: Based on these results, differences exist in neuromuscular functions and biomechanics between healthy individuals and those with CAI when performing the SEBT. A rest interval time of 20 seconds between trials during the SEBT is an appropriate time to discriminate joint CAs of TIR/DF and TIR/EV between healthy individuals and those with CAI during the SEBT. These findings have implications for treatment and possible prevention of CAI.

Study 1: Neuromuscular training improves movement competency and physical performance measures in 11-13 year old female netball athletes The purpose of this study was to examine the effects of a neuromuscular training program on movement competency and measures of physical performance in youth female netball players. It was hypothesized that significant improvements would be found in movement competency and physical performance measures following the intervention. Twenty-three junior female netball players (age, 12.17 ± 0.94 yrs; height, 1.63 ± 0.08 m; weight, 51.81 ± 8.45 kg) completed a test battery before and after a six-week training intervention. 13 of these athletes underwent six weeks of neuromuscular training, which incorporated plyometrics and resistance training. Trained athletes showed significant improvements in 20 m sprint time, 505 agility time, countermovement jump height and peak power (p ≤ 0.05, g > 0.8). Additionally, trained athletes significantly improved their score in the Netball Movement Screening Tool (NMST) (p < 0.05, g > -1.30); while the athletes also demonstrated increased reach in the anterior and posteromedial directions for the right and left leg, and in the posterolateral direction for the left leg only in the Star Excursion Balance Test (SEBT) (p < 0.05, g > -0.03). Control subjects did not exhibit any significant changes during the 6-week period. Significant negative correlations were found between improved score on the NMST and decreased 5 m, 10 m and 20 m sprint time, and 505 change of direction time (r > 0.4, p ≤ 0.05). Results of the study affirm the hypothesis that a six-week neuromuscular training intervention can improve performance and movement competency in youth netball players Study 2: Neuromuscular training improves lower extremity biomechanics associated with knee injury during landing in 11-13 year old female netball athletes. The purpose of this study was to examine the effects of a neuromuscular training program on lower extremity biomechanics in youth female netball athletes. The hypothesis was that significant improvements would be found in landing biomechanics of the lower extremities, commonly associated with anterior cruciate ligament (ACL) injury. Twenty-three athletes (age = 12.2 ± 0.9 yrs; height = 1.63 ± 0.08 m; weight = 51.8 ± 8.5 kg) completed two testing sessions separated by six weeks. Thirteen athletes underwent six weeks of neuromuscular training, while the remaining 13 served as controls. Three dimensional lower extremity kinematics and kinetics were measured during two landing tasks. Neuromuscular training significantly improved hip abduction angle and bilateral knee valgus motion in the bilateral landing task at maximum knee-flexion range of motion and knee internal rotation angle during the unilateral landing at maximum knee flexion-extension range of motion (p ≤ 0.05, g > 1.00). Additionally, the experimental group showed large, significant decreases in vertical ground reaction force in both landing tasks (p ≤ 0.05, g > -1.30). Control participants did not make any significant changes during the six-week study period. Results of the study affirm the hypothesis that a six week neuromuscular training program can enhance movement biomechanics associated with ACL injury.

Ce travail de thèse visait à déterminer l’influence de la durée et du niveau d’entraînement en endurance sur les mécanismes de régulation de la fatigue neuromusculaire et d’une stratégie de modulation de ces mécanismes sur la performance motrice. Ce travail de thèse consistait également à élaborer une nouvelle méthode d’entraînement permettant d’optimiser les stimuli responsables des adaptations résultantes d’un programme de conditionnement physique. Les résultats principaux issus de ces travaux sont présentés dans un résumé plus détaillé en fin de manuscrit
The present work aimed to determine the influence of exercise duration and endurance training level on the mechanisms underlying neuromuscular fatigue regulation and the effect of a deceptive strategy on exercise performance. This thesis also aimed to elaborate a new training method that would optimize exercise-induced training stimuli that are known to trigger complementary physical abilities adaptations. The main outcomes of these works are detailed in an expanded abstract at the end of the manuscript

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Muscle fatigue is a phenomenon that promotes physiological and biomechanical disorders and their changes in healthy subjects have been widely studied and have significant importance for care in preventing injuries, but we do not have many information about its effects in patients after ACL reconstruction. Thus, this study is to analyze the effects of fatigue on neuromuscular behavior of quadriceps after ACL reconstruction. To reach this objective, participants were forty men, twenty healthy (26,90 ? 6,29 years) and twenty after ACL reconstruction (29,75 ? 7,01 years) with a graft of semitendinosus and gracilis tendons, between four to six months after surgery. At first, there was an assessment of joint position sense (JPS) at the isokinetic dynamometer at a speed of 5?/s and target angle of 45? to analyze the absolute error of JPS. Next, we applied the a muscle fatigue protocol, running 100 repetitions of isokinetic knee flexion-extension at 90?/s. Concurrently with this protocol, there was the assessment of muscle performance, as the peak torque (PT) and fatigue index, and electromyographic activity (RMS and median frequency). Finally, we repeated the assessment of JPS. The statistical analysis showed that patients after ACL reconstruction have, even under normal conditions, the amended JPS compared with healthy subjects and that after fatigue, both have disturbances in the JPS, but this alteration is significantly exacerbated in patients after ACL reconstruction. About muscle performance, we could notice that these patients have a lower PT, although there are no differences between the dynamometric and EMG fatigue index. These findings show the necessity about the cares of pacients with ACL reconstruction in respect of the risks of articulate instability and overload in ligamentar graft
A fadiga muscular ? um fen?meno que envolve dist?rbios fisiol?gicos e biomec?nicos. A an?lise de suas altera??es, em indiv?duos sadios, possui grande import?ncia na preven??o de les?es, mas pouco se sabe sobre suas repercuss?es em pacientes ap?s reconstru??o do LCA. Dessa forma, o objetivo deste estudo foi avaliar os efeitos da fadiga no comportamento neuromuscular do quadr?ceps femoral de indiv?duos ap?s reconstru??o do LCA. Para tanto, participaram deste estudo quarenta homens, sendo vinte saud?veis (26,90 ? 6,29 anos) e vinte ap?s reconstru??o de LCA (29,75 ? 7,01 anos) com enxerto dos tend?es semitendinoso e gr?cil, entre 4 a 6 meses de p?s-operat?rio. Em princ?pio, realizou-se uma avalia??o do senso de posi??o articular (SPA) ativo, no dinam?metro isocin?tico, a uma velocidade de 5?/s e ?ngulo-alvo de 45?, sendo a vari?vel analisada o seu erro absoluto. Em seguida, aplicou-se uma avalia??o isom?trica m?xima em extens?o do joelho, a 60? de flex?o, por 10 segundos e um protocolo de fadiga muscular, sendo executadas 100 repeti??es isocin?ticas conc?ntricas de flexo-extens?o do joelho a 90?/s. Concomitantemente a esse protocolo, realizou-se a avalia??o do desempenho muscular, observando o pico de torque (PT), o ?ndice de fadiga (IFD) e a atividade eletromiogr?fica (Root Mean Square - RMS e freq??ncia mediana - Fm). Por fim, repetiu-se a avalia??o da SPA. As avalia??es detectaram que pacientes ap?s reconstru??o do LCA apresentaram, ainda em condi??es pr?-fadiga, o SPA alterado quando comparado com indiv?duos sadios e que quando fatigados, ambos possu?ram dist?rbios no SPA, sendo que essa altera??o foi significativamente mais exacerbada em pacientes ap?s reconstru??o de LCA. Quanto ao desempenho muscular, constatou-se que esses pacientes apresentam um menor PT, RMS e Fm quando comparado ao grupo controle, mas n?o possuem diferen?as quanto ao ?ndice de fadiga, dado pela Fm e pela dinamometria. Ademais, constatou-se que as vari?veis isocin?ticas e eletromiogr?ficas, em sua grande maioria, apresentam correla??es positivas. Os achados refor?am a necessidade dos cuidados aos pacientes ap?s reconstru??o do LCA, quando submetidos ? fadiga, no que diz respeito aos riscos de instabilidade articular e sobrecarga do enxerto ligamentar

Thesis Title: Enhancing rehabilitation following anterior cruciate ligament reconstruction. Context: Physical training with a neuromuscular focus has been shown to reduce anterior cruciate ligament (ACL) injury. However, ACL injury remains prevalent and often leads to joint instability, which requires surgical reconstruction. Following reconstructive surgery, a minimum of 6 months supervised rehabilitation is recommended with associated with financial cost implications to the National Health Service (NHS), the patient and society. Traditionally rehabilitation is offered in a concurrent format, whereby strength and cardio-vascular endurance exercises are performed in the same session. However, accumulating evidence from healthy populations, suggests that the development of strength might be attenuated by cardio-vascular endurance conditioning performed in close temporal proximity. This thesis comprises an entirely novel investigation of potential attenuation of strength gains in rehabilitating clinical populations that is associated with temporal incompatibility of physiological conditioning stimuli. No study has previously investigated this phenomenon, whether it might compromise the efficacy of treatment or recovery, or its potential influence on objectively-measured and patients’ perception of functional, musculoskeletal and neuromuscular performance capabilities. Objectives: The purpose of this thesis was to assess the effects of reconstruction surgery and 24 weeks of non-concurrent strength and endurance rehabilitation (with 48 week post-operative follow-up) on (a) subjective (IKDC; KOOS; PP [Chapter 4]) and objective measures of function (HOP [Chapter 5]) (primary outcome measures for this thesis), and (b) objective measures of musculoskeletal (ATFD) and neuromuscular performance (PF, EMD, RFD, SMP [Chapter 5]) (secondary outcome measures), in patients with anterior cruciate ligament deficiency. The secondary aim was to evaluate the relationships amongst a subjective outcome of function (IKDC), an objective outcome of function (HOP), and the secondary objective outcomes of musculoskeletal (ATFD) and neuromuscular (PF, RFD, EMD, SMP) performance at pre-surgery and at 24 weeks post-surgery (Chapter 6). Setting: Orthopaedic Hospital NHS Foundation Trust. Design: Prospective random-allocation to group trial involving iso-volume rehabilitative intervention versus contemporary practice, using contralateral limb assessment and clinico-social approbation controls. The design compared the effects of experimental post-surgical rehabilitation comprising non-concurrent strength and endurance conditioning with two conditions of control reflecting contemporary clinical practice (matched versus minimal assessment interaction). Participants: Eighty two patients (69♂, 13♀, age: 35.4 ± 8.6 yr; time from injury to surgery 9.4 ± 6.9 months [mean ± SD]) electing to undergo unilateral ACL reconstructive surgery (semitendinosus and gracilis graft [n = 57]; central third, bone-patella tendon-bone graft [n = 25]); were allocated to groups (2:2:1 purposive sampling ratio, respectively). Nineteen patients were lost to follow-up. Intervention: A standardised traditional concurrent (CON) ACL rehabilitation programme acted as the control versus an experimental non-concurrent (NCON) ACL rehabilitation programme that involved separation of strength and cardio-vascular endurance conditioning. An additional control group (Limited testing CON) matched the CON group rehabilitation applied within contemporary clinical practice. Outcome Measures: Chapter 4: The self-perceived primary outcome measures of function IKDC, KOOS and PP were assessed on five separate occasions (pre-surgery, and at 6, 12, 24 and 48 weeks post-surgery). However, assessment occasions were purposefully reduced to pre-operative and 48 weeks post-operative for the Limited testing CON group. Chapter 5: The primary objective outcome of function was HOP; the secondary outcomes were ATFD, PF, RFD, EMD and SMP associated with the knee extensors and flexors of the injured and non-injured legs. These objective outcomes were assessed on five separate occasions (pre-surgery, and at 6, 12, 24 and 48 weeks post-surgery). However, assessment occasions were purposefully reduced to pre-operative and at 48 weeks post-operative only for the Limited testing CON group. Chapter 6 Self-perceived (IKDC) subjective knee evaluation and the objective outcome of function (HOP), and selected objective outcomes of musculoskeletal and neuromuscular performance including ATFD, PF, RFD, EMD and SMP of the knee extensors and flexors of the injured and non-injured legs where applicable; measured at pre-surgery and at 24 weeks post-surgery were analysed for association, using Pearson product-moment correlation coefficients. A priori alpha levels were set at p<0.05. Results: Chapter 4: Factorial analyses of variance (ANOVAs) with repeated-measures investigating the primary aim showed significant group (NCON; CON) by test occasion (pre-surgery, 6, 12. 24 and 48 weeks post-surgery) interactions for self-perceived outcomes of function IKDC, KOOS and PP confirmed increased clinical effectiveness of NCON conditioning (F(2.0, 82.9)GG = 4.0 p<0.05, F(2.2, 134.7)GG = 5.5 p<0.001, F(1.9, 121.4)GG = 14.6 p<0.001, respectively) and the group mean peak relative difference in improvement for NCON was ~5.9% - 12.7% superior to CON. The greatest interaction effect was found to occur between pre-surgery and the 12 weeks post-operative test occasion for IKDC and KOOS, and between pre-surgery and the 24 week test occasion for PP. Patterns of improvements in self-perceived fitness over time were represented by a relative effect size range of 0.71 to 1.92. Improvement patterns were not significantly different between control groups offering matched or minimised assessor-patient interaction (CON vs. Limited testing CON; pre-surgery vs. 48 weeks post-surgery) indicating that clinical approbation by patients had not contributed to the outcome. Chapter 5: Factorial analyses of variance (ANOVAs) with repeated-measures showed significant group (NCON; CON) by leg (injured/non-injured) by test occasion (pre-surgery, 6, 12, 24 and 48 weeks post-surgery) interactions of the objective measure of function (HOP) together with the secondary outcomes of ATFD, PF, RFD, EMD and SMP. Similar responses were noted for the knee extensors and flexors of the injured and non-injured legs (F(2.1, 248) GG = 4.5 to 6.6; p<0.01) and confirmed increased clinical effectiveness of NCON conditioning (range ~4.7% - 15.3% [10.8%]) better than CON between 12 and 48 weeks. Patterns of improvements in physical fitness capabilities over time were represented by a relative effect size range of 1.92 to 2.89. Improvement patterns were not significantly different between control groups offering matched or minimised assessor-patient interaction (CON vs. Limited testing CON; pre-surgery versus 48 weeks post-surgery) indicating that clinical approbation by patients had not contributed to the outcome. Chapter 6: Two-tailed probabilities were used due to the exploratory nature of this study. A limited number of weak to moderate statistically significant correlations were confirmed (ranging from r = 0.262 – 0.404; p<0.05; n=48 [amalgamated NCON and CON groups] ) between IKDC and most notably, the neuromuscular performance outcome of EMD. Conclusion: Overall, the patterning and extent of changes amongst self-perceived, functional, musculoskeletal and neuromuscular performance scores offer support for the efficacy of using non-concurrent strength and endurance conditioning to enhance post-surgery rehabilitation. The limited robustness of relationships amongst the validated and frequently-used self-perceived outcome of function [IKDC], and objectively-measured outcomes of function and musculoskeletal and neuromuscular performance suggested that each might properly reflect an important but separate aspect of clinical response and should be deployed to detect change.

O objetivo do presente estudo foi analisar os efeitos da execução prévia de exercício físico e cognitivo sobre os componentes central e periférico da fadiga neuromuscular durante um teste contrarrelógio de 4 km de ciclismo. Para tanto, oito ciclistas treinados (n = 8) participaram de três diferentes estudos. No estudo 1, os atletas realizaram o teste contrarrelógio após assistir documentário (CON) ou após tarefa cognitiva (TC). No estudo 2, o teste de 4 km de ciclismo foi realizado após 100 drop jumps (DJ), 48 horas após 100 drop jumps (48h-DJ) e sem a realização prévia de exercício (CON). No estudo 3, o teste contrarrelógio foi realizado após fadiga prévia de membros superiores (FB) e inferiores (FP) e sem fadiga prévia (CON). Em todos os estudos, parâmetros de fadiga central e periférica foram avaliados por meio da técnica de estimulação elétrica no nervo femoral em repouso, pré e pós 4km de ciclismo. Estudo 1: O desempenho foi similar (P> 0,05) entre CON (376 ± 26,9 s) e TC (376,3 ± 26 s). Do mesmo modo, não encontramos diferenças significativas (P> 0,05) para parâmetros de fadiga central e periférica entre CON e TC. Estudo 2. O desempenho foi significativamente (P< 0,05) prejudicado em DJ (-2,3%) e houve uma tendência em 48h-DJ (-1,8%). A redução no desempenho em 48h-DJ foi devido à menor potência na parte inicial da prova (P< 0,05). Em DJ a piora no desempenho foi em decorrência de menor potência (P< 0,05) na parte inicial e final da prova. Houve uma exacerbada (P< 0,05) fadiga periférica após o contrarrelógio em DJ (1Hzpot= -44,7%) comparado com CON (1Hzpot= -20,1%). Além disso, significante fadiga de baixa frequência foi observada em DJ comparado com CON. Por outro lado, parâmetros de fadiga central e periférica apresentaram valores similares entre CON e 48h-DJ (P> 0,05). No entanto, foi encontrado aumento significativo (P< 0,05) na dor muscular tardia em 48hDJ comparado com CON e DJ. Estudo 3: O desempenho foi reduzido em FP (-2,3%) e FB (-1,5%) quando comparado com CON. O menor desempenho nas condições FP e FB foi acompanhado por redução na potência (P< 0,05) na parte inicial (condição FP) e na parte final (condições FP e FB) a prova. Ao final dos 4 km de ciclismo, os participantes apresentaram menor (P< 0,05) fadiga periférica em FB (1Hzpot= -11,9%) comparado com CON (1Hzpot= -20,1%). Em FP, houve maior fadiga periférica em comparação a condição CON e FB. Em conclusão, os resultados destes estudos sugerem que apenas a execução prévia de exercício envolvendo a musculatura utilizada no ciclismo promove alterações nos componentes periféricos da fadiga neuromuscular após 4 km de ciclismo
The aim of this study was to analyze the effects of previous execution of physical exercise and cognitive on the central and peripheral components of the neuromuscular fatigue during a 4 km cycling time trial. Eight trained cyclists (n = 8) participated of three different studies. In study 1, the athletes performed the 4 km cycling time trial test after watching a documentary (CON) or after a cognitive task (CT). In study 2, the 4-km cycling test was performed after 100 drop jumps (DJ), 48 hours after 100 drop jumps (48h-DJ) and without previous exercise (CON). In study 3, the time trial was performed after pre-fatigue of the upper (FU) and lower (FL) body and without prefatigue (CON). In all studies, central and peripheral fatigue parameters were evaluated via electrical stimulation in femoral nerve at rest, before and after 4km cycling. Study 1: Performance was similar (P> 0.05) between CON (376 ± 26.9 s) and TC (376.3 ± 26 s). Likewise, we found no significant differences (P> 0.05) for parameters of central and peripheral fatigue between CON and CT. Study 2: Performance was significantly (P< 0.05) impaired in DJ (-2.3%) and there was a trend in 48h-DJ (-1.8%). This reduction in performance in 48h-DJ was due to a lower power at first part of the time trial (P< 0.05). In DJ condition, loss in performance was due to lower power (P< 0.05) at the start and end phases of the test. There was exacerbated (P <0.05) peripheral fatigue after the time trial in DJ (1Hzpot = -44.7%) compared to CON (1Hzpot = 20.1%). Furthermore, a significant low frequency fatigue was observed in DJ compared to CON. On the other hand, central and peripheral fatigue parameters showed similar values between CON and 48h-DJ (P> 0.05). However, a significant increase in delayed onset muscle soreness was found in 48h-DJ than CON and DJ. Study 3: Performance was reduced in FU (-2.3%) and FL (-1.5%) compared to CON. The lowest performance was accompanied by a reduction in power (P< 0.05) in the initial (FL) and final (FL and FU phases of the time trial. After 4 km cycling, participants had a lower (P< 0.05) peripheral fatigue in FU (1Hzpot = -11.9%) compared with CON (1Hzpot = -20.1%). In FL, there was a greater peripheral fatigue compared to CON and FB condition. In conclusion, the results of these studies suggest that only the previous execution of exercise involving the muscles used in cycling causes changes in the peripheral components of the neuromuscular fatigue after 4 km of cycling

The asymmetries detected in the different multi-directional sports vary in magnitude depending on the test selected. Furthermore, in the individual analysis of the different tests administered, it was observed that athlete’s lower limb preferences depended on the test. Greater asymmetries were detected in the vertical jump test, the CODD variable, and the change of direction with inertial resistance test in multidirectional sports. The change of direction with inertial resistance test also enabled us to detect asymmetries in actions that approximate the actual sport. Moreover, the results showed that asymmetries have a negative impact on performance of the jump and the change of direction, and on speed in the linear sprint and the capacity to repeat the change of direction. Last, we were able to observe that iso-inertial training results in greater adaptations in performance and larger reductions in asymmetries than conventional cable-resistance training. We can also affirm that positive adaptations in performance caused by resistance training are not necessarily associated with reduced asymmetries
Com a síntesis d’aquest procés d’investigació, les asimetries detectades en els diferents esports multidireccionals mostren variabilitat en les magnituds segons la prova seleccionada. A més, en l’anàlisis individuals les proves realitzades, s’ha pogut observar que els esportistes mostren preferències en l’habilitat de la cama en funció de la prova. El test de salt vertical, la variable del COD i canvi de direcció amb resistència iso-inercial mostra majors magnituds en la detecció d’asimetries en esports multidireccionals. El canvi de direcció amb resistència iso-inercial permet, detectar les asimetries en accions pròximes a l’esport. Per un altre costat, els nostres resultats també mostren que les asimetries influeixen negativament en el rendiment de salt, canvi de direcció, capacitat de repetir canvis de direcció i velocitat en esprint lineal. Per a finalitzar, hem pogut observar que l’entrenament iso-inercial provoca majors adaptacions en el rendiment i majors reduccions d’asimetries que l’entrenament de força convencional de cable gravitacional

Ce travail de thèse s'est intéressé à l'étude des facteurs permettant d'expliquer les performances fonctionnelles des membres inférieurs des personnes âgées. Dans une première étude, nous avons montré que la puissance maximale (Pmax) ainsi que sa composante appelée la vitesse optimale (Vopt) obtenues lors d'un test de force-vitesse des extenseurs du genou, sont des facteurs déterminants de la performance fonctionnelle des personnes âgées évaluées sur 3 tests : marche sur 6m, se relever et s'assoir 5 fois de suite à partir d'une chaise et monter 6 marches d'escalier. Ainsi, plus une personne possède une Pmax et une Vopt élevées, plus ses performances lors de tests fonctionnels seront élevées. De plus, la Vopt étant considérée comme une évaluation indirecte du pourcentage de fibres rapides, les sujets ayant les plus grandes valeurs de Vopt sont les plus performantes aux tests fonctionnels. La deuxième étude a mesuré et comparé l'activité électromyographique (EMG) du quadriceps lors des tests de contraction isométrique volontaire maximal (IMVC), de détermination de la puissance maximale et des tests fonctionnels cités cidessus. La mesure du signal EMG au cours de ces différents tests a permis de déterminer dans quelle mesure le type de tâche induit une activation maximale ou non. Les personnes âgées montrent une capacité à davantage activer leurs quadriceps lors des tests de de contraction concentrique plutôt qu'isométrique ou excentrique. Les tests utilisant l'IMVC comparé aux tests de détermination de la puissance et de monté de marche, et de lever de chaise ne seraient pas les tests les plus appropriés pour mesurer les capacités maximales d'activation neuromusculaires chez la personne âgée. Il ressort de ces résultats une amélioration du testing de la personne âgée et des orientations pour la réhabilitation
This work has focused on the study of factors that explain the functionals performances of the lower limbs of the elderly. In a first study we showed that the maximum power (Pmax) and its component called the optimal speed (Vopt) obtained during a test of force-velocity of the knee extensors, are important determinants of functional performance elderly evaluated on three tests: walking on 6m, sit to stand 5 times from a chair and climbing 5 stairs. The more a person has a high Pmax and Vopt, the more its performance during functional tests will be. In addition, Vopt is considered an indirect assessment of the percentage of fast fibers; subjects with the highest values of Vopt are best performers during functional tests. The second study measured and compared the electromyographic (EMG) activity of the quadriceps when tested for isometric maximum voluntary contraction (IMVC), determination of maximum power and functional tests mentioned above. Measurement of EMG signal during these tests was used to determine to what extent the type of task induced a maximum activation or not. Older people show a greater ability to activate their quadriceps muscles when tested for concentric contraction rather than isometric or eccentric contractions. Tests using the IMVC compared to tests for determining the power, sit-tostand and stairs climbing would not be the most appropriate tests to measure the maximum neuromuscular activation capacity in the elderly. From these results improved testing of the elderly and guidelines for rehabilitation are proposed