Dissertations / Theses on the topic 'Concentric and eccentric load'
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1
Duhig, Steven J. "Hamstring strain injury: Effects of high speed running, kicking and concentric versus eccentric strength training on injury risk and running recovery." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/110637/1/Steven_Duhig_Thesis.pdf.
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The hamstring strain injury is a common and problematic injury within sports that involve high-speed running and kicking. This program of research has provided novel insights regarding the relationship between high speed running volumes and hamstring injuries, the effects of kicking on risk factors for hamstring strain and the muscular adaptations induced by concentric and eccentric hamstring exercises.
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Lawrence, Michael A. "Effects of elastic resistance on concentric force, concentric power, and eccentric velocity during the bench press." CardinalScholar 1.0, 2010. http://liblink.bsu.edu/uhtbin/catkey/1567419.
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Elastic bands are becoming more popular in strength and power training. Although increases in strength and power have been anecdotally reported with high loads of elastic resistance, there is no research on large band tensions and their effects on force and power variables. The purpose of this study was to quantify peak concentric force, peak concentric power and peak eccentric velocity produced by the subject when using differing levels of elastic resistance (0%, 20%, 50% and 75% of the total load being elastic resistance) in the bench press. Seven experienced male powerlifters and body builders participated in this study. Prior to subject testing all elastic bands were calibrated for force output throughout the bench press range of motion. Each subject performed a single repetition maximum press to determine the total correct testing load (85% of maximum press). The subjects then performed four presses with various elastic band resistances, each having the total equivalent weight of 85% of the subject’s maximal press weight at lockout. Dependent variables were peak concentric force, peak concentric power, and peak eccentric velocity as produced by the subject. A one-way ANOVA was used to determine the differences among the four levels of elastic resistance (ER) used in the study (α =
0.05). Compared to the baseline condition (2123.6 ± 499.9N), significantly lower average peak concentric force was observed with ER of 75% (1451.2 ± 151.0N, 31.9% decrease) (p = .010) and with an ER of 50% (1781.1 ± 174.3N, 16.4% decrease) (p = .052). When compared with baseline peak concentric power (702.6 ± 274.6W), higher peak power was observed in all band trials: 20% (895.2 ± 187.7W, 27.4% increase), 50% (972.5 ± 189.8W, 38.4% increase) and 75% (979.6 ± 171.0W, 39.4% increase) (p = .009; p = .007; p = .033, respectively). There was no significant difference in peak concentric power in any ER trials. No significant differences (p = .080) were seen in peak eccentric velocity. Therefore ER loads of 20, 50 and 75% provide greater stimuli for producing peak concentric power than no ER, with only a 20% load of ER maintaining the same peak concentric force production as baseline. ER loads of 50 and 75% may not be as effective a stimuli as free weights when the training objective is to increase force production.School of Physical Education, Sport, and Exercise Science
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Gault, Mandy Lucinda. "Adaptations of older adults to concentric and eccentric endurance exercise." Thesis, University of Chichester, 2010. http://eprints.chi.ac.uk/813/.
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The first aim was to examine in older adults the acute physiological effects of eccentric exercise (i.e. downhill treadmill walking, DW: -10% gradient, 30-min) at a self-selected walking speed. The secondary aim was to examine in older adults the effects of a 12-week concentric (level treadmill walking, LW: 0% gradient) and eccentric (downhill treadmill walking, DW: -10% gradient) endurance exercise intervention (30-min, 3x week) at a self-selected walking speed (SSWS, re-evaluated every 4-weeks) on the functional and physiological adaptations. Participants were randomly assigned to an exercise group (LW: 0=13 or DW: n=IS). Eighteen participants (8 LWand 10 DW) completed the 12-week intervention. Wearing the Cosmed K4b2 portable metabolic system had no effect on performance and physiological responses during the I-mile Rockport Fitness Walking Test (Study I).
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Deighan, Martine Annette. "The development of concentric and eccentric leg and arm strength." Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393145.
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Kellis, Eleftherios. "Muscle activation and joint loading during isokinetic eccentric and concentric exercise." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321116.
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Kudiarasu, Christine. "Effects of eccentric versus concentric resistance training in adults with Type 2 Diabetes." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2020. https://ro.ecu.edu.au/theses/2297.
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The benefits of resistance training for people with Type 2 diabetes (T2D) are well documented; however, the effects of different muscle contraction types (e.g. eccentric, concentric) on physiological outcomes for this population are still unclear. This study investigated the effects of eccentric (ECC) versus concentric (CON) resistance training on blood markers, muscle strength, physical functional performance and body composition. Eighteen adults with T2D (Age: 64.8 ± 9.0 y; BMI: 30.3 ± 4.1 kg/m2) were randomly assigned to either an ECC (n = 9) or a CON (n = 9) group. Participants performed 2 or 3 sets of 10 eccentric (5-s) or concentric (2-s) contractions of eight upper and lower body resistance exercises, twice a week for 12 weeks. Training intensity gradually increased from 10 to 100% of 1-repetition maximum concentric strength (1-RM) for the ECC group and from 50 to 100% of 1-RM strength for the CON group, based on the 1-RM at baseline. Blood markers (glucose, insulin, HbA1c, HOMA2-IR, cholesterol, triglycerides, HDL and LDL), muscle strength (1- RM), body composition (dual-energy x-ray absorptiometry), and physical functional performance tests consisting of 6-min walk (6MWT), chair rise (CR), timed up-and-go (TUG), and balance were measured before and after the intervention, and the changes were compared between groups. Significant differences in the improvement between the ECC and CON group were found for 1-RM strength for bicep curl (ECC: 11%, CON: 27%), calf raise (ECC: 37%, CON: 68%) and abdominal crunch (ECC: 22%, CON: 42%) exercises, hip circumference (ECC: -1%, CON: -5%) and SF-36 pain measures (ECC: 6%, CON: -1%). Muscle strength significantly increased more for the CON group (27–68%) than the ECC group (12–37%) which was likely due to greater combined total load lifted in the CON (143,262 ± 57,972 kg) than the ECC group (111,678 ± 51,225 kg). Significant improvements (p < 0.05) were also found in the ECC group for the 6MWT (56.8 ± 2.2 m), TUG (-0.8 ± 0.3 s) and CR (-1.8 ± 1.4 s), while the CON group significantly improved the 6MWT (63.4 ± 12.0 m) and CR (-2.3 ± 1.6 s). Total equilibrium balance increased by 7.0% in the ECC group and 4.3% in the CON group. Body composition improved similarly for both groups including significant reductions in total fat mass (ECC: -2.0 ± 1.3 kg, CON: -2.2 ± 1.2 kg) and significant increase in total lean mass (ECC: 1.8 ± 0.7 kg, CON: 2.0 ± 0.2 kg). No significant changes were found in blood markers for both groups. These results showed that ECC training performed at lower intensities (RPE: 4.1 ± 2.1) was as effective as CON training for improving physical functional performance, strength and body composition. These findings suggest that focusing on eccentric contractions in resistance training is beneficial and well-tolerated in adults with T2D.
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Fischer, Stephen Michael. "METABOLIC DIFFERENCES BETWEEN A BOUT OF ECCENTRIC, CONCENTRIC, AND TRADITIONAL RESISTANCE EXERCISE." Kent State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=kent1479465117642973.
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Shaw, I., BS Shaw, JF Cilliers, and DT Goon. "Influence of visual feedback on knee extensor isokinetic concentric and eccentric peak torque." African Journal for Physical, Health Education, Recreation and Dance, 2009. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001651.
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Abstract
Isokinetic normative data can be invaluable in identifying an individual’s strengths and
weaknesses, and thus lead to a more effective use of the individual’s time to minimise or
overcome his weaknesses while maintaining or improving existing strength. However, visual
feedback (VF) may significantly affect the result of isokinetic testing, resulting in erroneous
conclusions if not accounted for. Additionally, the previous use of VF to obtain increased
strength values has resulted in inconsistent findings. The purpose of this study was to examine
the effect of VF on concentric and eccentric knee extensor peak torque. Twenty-two sedentary,
college-aged male and female volunteers were assigned to either Group 1 (n = 11) or Group 2 (n
= 11) to either perform knee extensor concentric-eccentric (con-ecc) isokinetic testing with VF or
without VF (no-VF) using a crossover method. After a one-week rest, the two groups underwent
knee extensor con-ecc isokinetic testing using the alternative testing condition. Each test
consisted of five maximal knee extensor con-ecc isokinetic testing contractions at 60° per second
on the Cybex Norm system. The data indicated significant (p < 0.05) differences in the
concentric peak torque of Group 1, Group 2 and Combined Group following VF when compared
to no-VF. The eccentric peak torque of Group 1, Group 2 and Combined Group was found not to
be significantly different following VF when compared to no-VF. Further, no significant
interaction effect as a result of the different groups was found. Visual feedback of torque output
can improve maximum voluntary concentric contraction in isokinetic dynamometry, but not
maximum voluntary eccentric contraction. It is thus recommended that VF should be consistently
provided during isokinetic testing, since it can also be used to help detect and correct errors in
performance as well as derive reinforcement from correct performances.
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Razmislevičius, Darius. "Ekscentrinio koncentrinio prieškrūvio poveikis nesportuojančių asmenų vegetacinių sistemų rodikliams didelio intensyvumo darbe." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2006. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2006~D_20060516_103637-32433.
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The hypothesis. We supposed the fatigue and its residual phenomena generated by eccentric concentric load to have a different effect on the changes in vegetative indices during exercise of high aerobic intensity in particular.
The aim of the research was to establish the effect of eccentric concentric pre-load on the changes in vegetative indices during exercise of high intensity.
The tasks set were as follows: 1. To estimate the residual effect of eccentric pre-load on the changes in vegetative indices during exercise of high intensity. 2. To estimate the residual effect of eccentric-concentric pre-load on the changes in vegetative indices during exercise of high intensity. 3. To compare the residual effect of eccentric and eccentric-concentric pre-load on the vegetative indices, biochemical indices of blood during exercise of high intensity.
The subjects were 9 unsportsman persons, who gave their informed consent to take part in the experiments within the present study. They were distributed to two eksperimental groups. The first group carried out eccentric pre-load and the second group carried out eccentric-concentric pre-load.
The methods used were as follows: changes in the values of VO2, VCO2, heart rate (HR) and Ve indices of the subjects were established applying the test of continuously increased load and the test of constant load when pedalling the veloergometer. After testing blood of the subjects to establish lactate and Creatin-Kinase (CK) concentration in... [to full text]
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Raue, Ulrika. "Effects of concentric vs eccentric resistance training on skeletal muscle adaptations in humans." Virtual Press, 2001. http://liblink.bsu.edu/uhtbin/catkey/1221284.
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The Beothuk Indians were an extinct group of Amerinds who were among the earliest founders of Newfoundland. In literature, the Beothuk were described as perhaps being phenotypically more similar to Europeans than Asians (Gatschet 1890, Lloyd 1875, 1876a, Marshall 1996). In this research, mitochondrial DNA (mtDNA) analysis was performed on a Beothuk individual in order to determine his haplotype and, perhaps, shed light on the origins of the Beothuk.For this analysis, a tooth of Nonosabasut, a Beothuk chief who died in 1819 was loaned from the Royal Museum of Scotland. Ancient DNA was extracted from 172 mg of dentin from the tooth. The DNA was cut with two blunt-end restriction enzymes, RsaI and HaeIII. Double-stranded DNA adapters were ligated to the blunt ends. A single adapter was used to amplify the resulting fragments using PCR. In this manner, two libraries of the DNA were created that could be readily reamplified using a small amount of the PCR product. mtDNA type was determined by amplifying specific regions and performing Restriction Fragment Length Polymorphism analysis and sequencing. It was determined that the Beothuk individual had a 9-bp deletion at nucleotide position (np) 8272, an Alul restriction site at np 5176, and heteroplasmy for a HincII restriction site at np 13,259, indicating that the Beothuk individual falls into the Native American Haplogroup B. Haplogroup B is not present in modern Siberian populations, whereas the remaining Native American mtDNA haplogroups are. It has been hypothesized that Haplogroup B arrived in the Americas at a different time than haplogroups A, C, D, and X, about 16,000-13,000 YBP (Years Before Present) (Starikovskaya et al. 1998). Haplogroup B can be found in some modern Taiwanese, Japanese, Korean, Evenk, and other Asian populations.Sequencing of the D-Loop region revealed a G to A transition at np 16303. To our knowledge, this transition was never previously reported in a Native American. This transition has been reported in Tibetans, Koreans, Hans, and Japanese, all considered to be southeast Asian Causacoids (Torroni et al. 1993b, 1994b). This transition, also frequently described in the Caucasian Haplogroup H, is especially prevalent in Spain and among the Basque. It is described as a root haplotype of Haplogroup H whose expansion was estimated to be between 12,300-13,200 YBP (Torroni et al. 1998). This time estimate coincides with the expansion of Haplogroup B. One possible explanation for this transition may be some admixture of the Beothuk with a Caucasian population.School of Physical Education
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Chaudhry, Saira. "A biomechanical characterisation of eccentric and concentric loading of the triceps surae complex." Thesis, Queen Mary, University of London, 2013. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8401.
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This thesis presents a biomechanical characterisation of eccentric (EL) and concentric loading (CL) of the triceps surae. EL is commonly adopted as an effective treatment for Achilles tendinopathy, with notably better treatment success compared with CL. However, there is a lack of consensus about the most appropriate protocols for completing triceps surae exercises. Exercise parameters such as speed and load are important and may affect the stimuli sensed by the muscle-tendon unit and thus influence repair. This thesis aims to biomechanically characterise and compare EL and CL as a basis for trying to understand treatment effects. A measuring system comprising motion tracking, 2D ultrasound, force plates and EMG was adopted and a semi-automatic tracking algorithm developed to track the muscle-tendon junction throughout the loading cycle (Chapter 3). Having validated the accuracy of measurements (Chapter 4), the effect of variables such as speed of exercise (chapter 5) and addition of load (Chapter 6) were assessed on Achilles tendon force, stiffness, stress, strain and force perturbations as well as muscle activation and contraction frequency (Chapter 7), in healthy subjects. It was found that EL and CL do not differ in terms of tendon force, stiffness or strain. However, EL is characterised by lower muscle activation and by 10 Hz perturbations present within the tendon. These perturbations were found to be significantly dependent on movement speed and load applied during EL movements only. However, no effect of speed was found on tendon force, stiffness and strain during either exercise movement. Finally, temporo-spatial analysis of the calf revealed region specific variations in muscle activation during both EL and CL, with 10 Hz perturbations coming predominantly from medial soleus and medial gastrocnemius muscle activity. These studies provide new information about the biomechanics of EL or CL, which should enhance understanding, and development, of conservative Achilles tendinopathy management.
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Choueiri, George H. "An experimental study of natural convection in vertical open-ended concentric and eccentric annuli." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28436.
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The effects of eccentricity on the natural convection heat transfer from a vertical open-ended cylindrical annulus with diameter ratio of 1.63 and aspect ratio of 18:1 have been investigated experimentally. Measurements of transient and steady state wall temperature distributions for different eccentricities were collected to help understand the heat transfer processes and also to serve as benchmarks for the validation of future CFD studies. Particle image velocimetry was used to validate the calculated mass flow rate in the annulus. It was found that, whereas at very low eccentricities there was insensitivity to eccentricity on the overall heat transfer, a diminishing of the heat transfer occurred for higher eccentricities. Plots of the local azimuthal variation of the Nusselt number showed that at low eccentricities heat transfer improved on one side of the annulus but decreased on the other side. The Nusselt number was found to decrease with eccentricity, while the Rayleigh and Grashof numbers had an increasing trend. It was also found that the mass flow rate did not appear to be strongly influenced by varying eccentricity within the experimental range. The Reynolds number was calculated and the flow within the annulus was found to be transitional nearing laminar with increased distance from the inlet.
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Franchi, Martino V. "Mechanisms of human skeletal muscle remodeling in response to concentric and eccentric loading paradigms." Thesis, Manchester Metropolitan University, 2014. http://e-space.mmu.ac.uk/326244/.
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It is common knowledge that resistance exercise promotes muscle growth (hypertrophy) and increased strength and function: thus, regular exercise can help minimize the loss of muscle mass and function in healthy ageing. Skeletal muscle can contract by either shortening or lengthening (concentrically or eccentrically, respectively). A substantial number of studies focused on the effect of concentric versus eccentric training protocols on muscle morphological and functional changes: eccentric contractions are generally thought to result in more increased muscle hypertrophy and strength, because of the higher force produced by the muscle and the more severe exercise induced muscle damage, which may lead to a stronger adaptations in muscle remodeling and repair processes. Study 1 shows that ECC and CON exercise protocols lead instead to similar gains in muscle size, but through different architectural remodeling mechanisms: moreover, acute contraction-specific molecular responses have been characterised. Study 2 and Study 3 were then performed in order to gain novel insights into the relationship between these morphological adaptations and the metabolic responses (MPS, muscle protein synthesis) of human skeletal muscle in response to chronic ECC vs. CON loading paradigms. Study 2 was first carried out in order to validate the use of deuterium oxide isotope tracing technique for measuring changes in MPS in free-living subjects over longerterm periods (compared to normal AA infusion studies) of resistance exercise. After assessing the feasibility of deuterium oxide tracing technique in measuring MPS response during resitance-training protocols, study 3 investigated the chronic responses in MPS to ECC vs. CON loading in two 3 different sites of the human vastus lateralis, presenting novel insights into MPS and skeletal muscle homogeneity, attempting to link MPS changes to the different mechanisms of muscle morphological remodelling occurring after ECC vs. CON training.
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Gallagher, James Williams. "Stability of axial flow between concentric and eccentric circular cylinders disturbed asymmetrically and nonlinearly." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/12022.
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Butz, Travis M. "Tests on pultruded square tubes under eccentric axial load." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/21800.
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Yeo, Chow Chea. "Quantification of eccentric load using accelerometer imbedded in GPS." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2014. https://ro.ecu.edu.au/theses/1560.
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Global positioning system (GPS) with a triaxial accelerometer is widely used to monitor movements of athletes in games and training, and “body load” (BL) representing the accumulation of the rate of changes in three planes of movements is obtained to determine the training load of a session. Deceleration, change of directions and stopping require eccentric contractions of leg muscles, potentially causing muscle damage and affecting athletic performance. Thus, it is important to monitor eccentric loading in games and training. A variable known as “eccentric index” (EI) purports to be a better representation of eccentric loading than BL. However, it is not known whether BL or EI accurately represents eccentric loading. The present study compared BL and EI during a drill consisting of several movements requiring eccentric contractions of leg muscles (Study 1), and monitored BL and EI over four training sessions of football (soccer) together with changes in maximal voluntary contraction (MVC) strength of the knee extensors and muscle soreness of the thigh muscles before and after each training session (Study 2).
In Study 1, 11 university students performed a drill consisting of 3 segments separated by 2 vertical jumps (segment 1: 70 m, segment 2: 50 m, segment 3: 60 m) with several movements including half turns (approximately 45°), 90° and 180° turns and a stop for a total distance of 180 m. All subjects performed the drill at 30%, 60% and 100% of their perceived maximal velocity, 2 trials for each velocity with a 5-min rest between trials. The same trials were repeated on two different days separated by at least 2 days. The time to complete the drill was measured by timing gates, and the time to complete each segment and entire distance, BL (GPSports, Australia) and EI (Athletic Data Innovations, Australia) of each segment were calculated from the GPS/accelerometer data using a specific software. One-way ANOVA compared the three velocities and three segments for the time, BL and EI, and a Pearson product-moment correlation was used to examine the relationships between them. The time to complete the drill was 102.9 ± 15.2 s for 30%, 56.3 ± 5.6 s for 60%, and 42.6 ± 3.1 s for maximum (100%) velocity, with each significantly different from the others (p
In Study 2, 6 state league level outfield football (soccer) players were monitored for 4 training sessions, each lasting for 90-120 minutes. BL and EI were calculated as per Study 1 and MVC strength and muscle soreness were assessed before and 1 day after each training session. BL and EI were similar across the 4 sessions; however a large variability in the EI was evident among the players. It was found that a high EI player had a high total mechanical work (total accumulation of changes of directions, accelerations and decelerations). No significant correlation was found between BL and EI, indicating that BL and EI showed different aspects of the movements. No significant changes in MVC strength and muscle soreness were observed after any training session, suggesting that muscle damage was not induced, because of the protective effect conferred by regular training.
From the two studies, it was concluded that EI was a better marker to quantify eccentric load than BL, however it is still unclear how accurately EI represents actual muscle damage of leg muscles, which warrants further studies
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MacMillan, Norah. "Comparison of skeletal muscle adaptations to eccentric versus concentric training in chronic obstructive pulmonary disease." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119513.
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Currently, effective treatment strategies for patients with severe chronic obstructive pulmonary disease (COPD) are limited. A widely used treatment method is exercise rehabilitation, which has a multitude of benefits on quality of life, improving exercise tolerance and decreasing hospitalizations. However, patients with more severe cases of COPD are unable to train at exercise intensities high enough to significantly improve disease-related skeletal muscle abnormalities such as losses in muscle mass and strength. Our group has recently shown the feasibility and safety of an eccentric (ECC) cycle training intervention in COPD as an alternative modality that can load the muscle four times as much as typical concentric (CON) cycle training at the same metabolic cost (Rocha Vieira, Baril et al. 2011). However, the skeletal muscle adaptations to ECC cycling compared to CON cycling in COPD have not been examined in the literature. In our study, patients were randomized to either an ECC (n=8) or CON (n=7) cycle training group to train for 10 weeks, three times per week for 30 minutes and matched for metabolic cost at 60-80% CON V̇O2peak. Pre and post-training assessments were taken of the patient's body composition, peak muscle strength and muscle fiber type and size by immunolabeling cross-sections of vastus lateralis muscle needle biopsies. Compared to CON training, we found that ECC training resulted in significant increases in lean body mass with an accompanying decrease in body fat mass. Along with this we found that, ECC training resulted in significant increases in muscle strength, whereas CON training did not. At the single fiber level, we found that CON resulted in increases in average fiber size that was principally drive by an increase in type 1 fiber size, however no changes were seen in patients performing ECC training. In both groups no significant changes in fiber type proportions occurred with training. ECC cycling had a moderately greater augmenting effect on lean muscle mass and strength than CON cycling, making it a useful alternative for severe COPD patients due to its high force production at an equivalent metabolic cost, which may prove important in preventing disease related muscle atrophy.Actuellement, on constate un manque de stratégies de traitements efficaces pour les patientes atteints de maladie pulmonaire obstructive chronique (MPOC) sévère. Une méthode de traitement des plus répandues est l'exercice de réadaptation qui possède de nombreux bienfaits tels que l'amélioration de la qualité de vie, l'augmentation de la tolérance à l'effort et une diminution du nombre d'hospitalisations. Cependant, dans les cas les plus sévères plusieurs patients ne sont pas en mesure de faire de l'exercice à une intensité assez forte pour améliorer les anomalies des muscles squelettiques, une caractéristique importante de la MPOC, comme la perte de la masse musculaire, la force musculaire et un changement des proportions des fibres. Récemment, notre groupe de recherche a démontré la faisabilité et la sécurité d'une intervention en entraînement en cycle de musculation excentrique (EXC) dans les cas de MPOC. En effet, l'exercice excentrique permet d'ajouter 4 fois plus de résistance musculaire que l'entraînement en cycle concentrique (CONC) typique, et ce, au même cout métabolique. Par contre, les adaptations des muscles squelettiques au cycle EXC en comparaison à celles au cycle CONC dans les cas de MPOC n'ont pas été documentées dans les publications. Dans cette étude, les patients ont été randomisés en deux groupes, EXC (n=8) ou CONC (n=7) pour dix semaines d'entraînement, 3x par semaine pour 30 minutes pour un même coût métabolique CONC de 60-80% V̇O2max. Les mesures ont été prises avant et après l'entraînement : la composition corporelle, la force musculaire maximale, une biopsie à l'aiguille du vaste latéral pour l'analyse de l'expression protéinique MHC et pour la grandeur de la fibre musculaire. Les résultats ont démontré qu'en comparaison avec l'entraînement CONC, l'entraînement EXC permet une augmentation significative de la masse corporelle maigre accompagnée d'une diminution de la masse corporelle grasse. De plus, nous avons remarqué que l'entraînement EXC a résulté en une augmentation significative de la force musculaire, mais l'entraînement CONC n'a pas résulté en une augmentation significative de la force musculaire. Néanmoins, l'entraînement CONC a résulté en une augmentation plus grand de la grandeur des fibres en moyen et spécifique à fibres qui expresse le protéine MHC type 1. En les deux groupes, il n'y a pas un changement significatif des proportions des fibres après l'entraînement. L'entraînement EXC a résulté en une augmentation plus grande de la composition corporelle et la force musculaire que l'entraînement CONC. L'entraînement EXC est une alternative utile pour éviter la perte de la masse musculaire dans les patients plus sévère a cause de la diminution de la coûte métabolique et l'augmentation de la force musculaire pendant l'entraînement.
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Grigg, Nicole Lorraine. "The acute adaptations of normal and pathological human Achilles tendons to eccentric and concentric exercise." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/47048/1/Nicole_Grigg_Thesis.pdf.
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Eccentric exercise is the conservative treatment of choice for mid-portion Achilles tendinopathy. While there is a growing body of evidence supporting the medium to long term efficacy of eccentric exercise in Achilles tendinopathy treatment, very few studies have investigated the short term response of the tendon to eccentric exercise. Moreover, the mechanisms through which tendinopathy symptom resolution occurs remain to be established. The primary purpose of this thesis was to investigate the acute adaptations of the Achilles tendon to, and the biomechanical characteristics of, the eccentric exercise protocol used for Achilles tendinopathy rehabilitation and a concentric equivalent. The research was conducted with an orientation towards exploring potential mechanisms through which eccentric exercise may bring about a resolution of tendinopathy symptoms. Specifically, the morphology of tendinopathic and normal Achilles tendons was monitored using high resolution sonography prior to and following eccentric and concentric exercise, to facilitate comparison between the treatment of choice and a similar alternative. To date, the only proposed mechanism through which eccentric exercise is thought to result in symptom resolution is the increased variability in motor output force observed during eccentric exercise. This thesis expanded upon prior work by investigating the variability in motor output force recorded during eccentric and concentric exercises, when performed at two different knee joint angles, by limbs with and without symptomatic tendinopathy. The methodological phase of the research focused on establishing the reliability of measures of tendon thickness, tendon echogenicity, electromyography (EMG) of the Triceps Surae and the standard deviation (SD) and power spectral density (PSD) of the vertical ground reaction force (VGRF). These analyses facilitated comparison between the error in the measurements and experimental differences identified as statistically significant, so that the importance and meaning of the experimental differences could be established. One potential limitation of monitoring the morphological response of the Achilles tendon to exercise loading is that the Achilles tendon is continually exposed to additional loading as participants complete the walking required to carry out their necessary daily tasks. The specific purpose of the last experiment in the methodological phase was to evaluate the effect of incidental walking activity on Achilles tendon morphology. The results of this study indicated that walking activity could decrease Achilles tendon thickness (negative diametral strain) and that the decrease in thickness was dependent on both the amount of walking completed and the proximity of walking activity to the sonographic examination. Thus, incidental walking activity was identified as a potentially confounding factor for future experiments which endeavoured to monitor changes in tendon thickness with exercise loading. In the experimental phase of this thesis the thickness of Achilles tendons was monitored prior to and following isolated eccentric and concentric exercise. The initial pilot study demonstrated that eccentric exercise resulted in a greater acute decrease in Achilles tendon thickness (greater diametral strain) compared to an equivalent concentric exercise, in participants with no history of Achilles tendon pain. This experiment was then expanded to incorporate participants with unilateral Achilles tendinopathy. The major finding of this experiment was that the acute decrease in Achilles tendon thickness observed following eccentric exercise was modified by the presence of tendinopathy, with a smaller decrease (less diametral strain) noted for tendinopathic compared to healthy control tendon. Based on in vitro evidence a decrease in tendon thickness is believed to reflect extrusion of fluid from the tendon with loading. This process would appear to be limited by the presence of pathology and is hypothesised to be a result of the changes in tendon structure associated with tendinopathy. Load induced fluid movement may be important to the maintenance of tendon homeostasis and structure as it has the potential to enhance molecular movement and stimulate tendon remodelling. On this basis eccentric exercise may be more beneficial to the tendon than concentric exercise. Finally, EMG and motor output force variability (SD and PSD of VGRF) were investigated while participants with and without tendinopathy performed the eccentric and concentric exercises. Although between condition differences were identified as statistically significant for a number of force variability parameters, the differences were not greater than the limits of agreement for repeated measures. Consequently the meaning and importance of these findings were questioned. Interestingly, the EMG amplitude of all three Triceps Surae muscles did not vary with knee joint angle during the performance of eccentric exercise. This raises questions pertaining to the functional importance of performing the eccentric exercise protocol at each of the two knee joint angles as it is currently prescribed. EMG amplitude was significantly greater during concentric compared to eccentric muscle actions. Differences in the muscle activation patterns may result in different stress distributions within the tendon and be related to the different diametral strain responses observed for eccentric and concentric muscle actions.
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Hedlund, Mattias. "Biomechanical and neural aspects of eccentric and concentric muscle performance in stroke subjects : Implications for resistance training." Doctoral thesis, Umeå universitet, Sjukgymnastik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-55466.
Full textAbstract:
Muscle weakness is one of the major causes of post-stroke disability. Stroke rehabilitation programs now often incorporate the same type of resistance training that is used for healthy subjects; however, the training effects induced from these training strategies are often limited for stroke patients. An important resistance training principle is that an optimal level of stress is exerted on the neuromuscular system, both during concentric (shortening) and eccentric (lengthening) contractions. One potential problem for post-stroke patients might be difficulties achieving sufficient levels of stress on the neuromuscular system. This problem may be associated with altered muscular function after stroke. In healthy subjects, maximum strength during eccentric contractions is higher than during concentric contractions. In individuals with stroke, this difference in strength is often increased. Moreover, it has also been shown that individuals with stroke exhibit alteration with respect to how the strength varies throughout the range of motion. For example, healthy subjects exhibit a joint specific torque-angle relationship that normally is the same irrespective of contraction mode and contraction velocity. In contrast, individuals with stroke exhibit an overall change of the torque-angle relationship. This change, as described in the literature, consists of a more pronounced strength loss at short muscle length. In individuals with stroke, torque-angle relationships are only partially investigated and so far these relationships have not been analysed using testing protocols that include eccentric, isometric, and concentric modes of contraction. This thesis investigates the torque-angle relationship of elbow flexors in subjects with stroke during all three modes of contractions – isometric, concentric, and eccentric – and the relative loading throughout the range of movement during a resistance exercise. In addition, this thesis studies possible central nervous system mechanisms involved in the control of muscle activation during eccentric and concentric contractions. The torque-angle relationship during maximum voluntary elbow flexion was examined in stroke subjects (n=11), age-matched healthy subjects (n=11), and young subjects (n=11) during different contraction modes and velocities. In stroke subjects, maximum torque as well as the torque angle relationship was better preserved during eccentric contractions compared to concentric contractions. Furthermore, the relative loading during a resistance exercise at an intensity of 10RM (repetition maximum) was examined. Relative loading throughout the concentric phase of the resistance exercise, expressed as percentage of concentric torque, was found to be similar in all groups. However, relative loading during the eccentric contraction phase, expressed as the percentage of eccentric isokinetic torque, was significantly lower for the stroke group. In addition, when related to isometric maximum voluntary contraction, the loading for the stroke group was significantly lower than for the control groups during both the concentric and eccentric contraction phases. Functional magnetic resonance imaging was used to examine differences between recruited brain regions during the concentric and the eccentric phase of imagined maximum resistance exercise of the elbow flexors (motor imagery) in young healthy subjects (n=18) and in a selected sample of individuals with stroke (n=4). The motor and premotor cortex was less activated during imagined maximum eccentric contractions compared to imagined maximum concentric contraction of elbow flexors. Moreover, BA44 in the ventrolateral prefrontal cortex, a brain area that has been shown to be involved in inhibitory control of motor activity, was additionally recruited during eccentric compared to concentric conditions. This pattern was evident only on the contralesional (the intact hemisphere) in some of the stroke subjects. On the ipsilesional hemisphere, the recruitment in ventrolateral prefrontal cortex was similar for both modes of contractions. Compared to healthy subjects, the stroke subjects exhibited altered muscular function comprising a specific reduction of torque producing capacity and deviant torque-angle relationship during concentric contractions. Therefore, the relative training load during the resistance exercise at a training intensity of 10RM was lower for subjects with stroke. Furthermore, neuroimaging data indicates that the ventrolateral prefrontal cortex may be involved in a mechanism that modulates cortical motor drive differently depending on mode of the contractions. This might partly be responsible for why it is impossible to fully activate a muscle during eccentric contractions. Moreover, among individuals with stroke, a disturbance of this system could also lie behind the lack of contraction mode-specific modulation of muscle activation that has been found in this population. The altered neuromuscular function evident after a stroke means that stroke victims may find it difficult to supply a sufficient level of stress during traditional resistance exercises to promote adaptation by the neuromuscular system. This insufficiency may partially explain why the increase in strength, in response to conventional resistance training, often has been found to be low among subjects with stroke.Muskelsvaghet är en av orsakerna till funktionshinder efter stroke. I rehabiliteringsprogram för personer som drabbats av stroke förekommer det numera att styrketräning används i syfte att öka muskelstyrkan. Effekten av styrketräning har dock ofta visat sig vara begränsad. En viktig styrketräningsprincip är att muskulaturen belastas tillräckligt nära maximal styrka under både koncentriska kontraktioner (när man lyfter en vikt) och excentriska kontraktioner (när man kontrollerat sänker en vikt). Ett potentiellt problem skulle kunna vara att personer med stroke inte belastas optimalt under träning på grund av förändrad muskelfunktion. Efter stroke är muskelfunktionen ofta förändrad såtillvida att styrkenedsättningen är mer uttalad under koncentriska kontraktioner. Därutöver har man funnit att styrkenedsättningen är mest uttalad när muskeln är i sitt mest förkortade läge. Detta fenomen har dock inte studerats för alla tre kontraktionstyper, det vill säga excentriska, koncentriska och isometriska kontraktioner, hos personer med stroke. Denna avhandling undersöker sambandet mellan styrka och ledvinkel över armbågsleden hos personer med stroke under alla tre kontraktionstyper – excentrisk, koncentrisk och isometrisk, samt relativ belastning genom rörelsebanan under en styrketräningsövning. Därutöver undersöker denna avhandling också hjärnans aktiveringsmönster under excentriska och koncentriska kontraktioner. Sambandet mellan styrka och ledvinkel undersöktes hos personer med stroke (n = 11), åldersmatchade (n = 11) och unga försökspersoner (n = 11). Jämfört med kontrollgrupperna var maximal styrka för personer med stroke mest nedsatt, samt även den oproportionerligt stora styrkenedsättningen vid kort muskelängd som mest uttalad, under koncentriska kontraktioner. Denna avvikelse var minst uttalad vid excentriska kontraktioner. Vidare studerades hur hög belastningen på muskulaturen var i jämförelse med muskelns maximala styrka under en styrketräningsliknande övning för armbågsflexorer vid en träningsintensitet på 10RM. Den uppmätta belastningen under den koncentriska fasen av styrketräningsövningen, uttryckt som procent av den genomsnittliga koncentriska styrkan, var densamma för alla grupperna. Under den excentriska fasen av övningen var dock belastningen, uttryckt som procent av den maximala excentriska styrkan, signifikant lägre för personer med stroke. Träningsbelastningen utgjorde också en lägre andel av den maximala isometriska styrkan för personer med stroke, både under den koncentriska och under den excentriska fasen. Funktionell magnetresonanstomografi (fMRI) användes för att undersöka hjärnans aktiveringsmönster hos unga försökspersoner (n = 18) och hos individer med stroke (n = 4) när de föreställde sig att de utförde maximal styrketräning för armbågsflexorer (motor imagery). Resultatet visade att primära motorbarken och premotoriska barken var mindre aktiverade när unga friska försökspersonerna föreställde sig utföra maximala excentriska, jämfört med maximala koncentriska kontraktioner. Dessutom var en region i ventrolaterala prefrontala barken, som i tidigare studier visat sig vara inblandat i reglering och hämning av muskelaktivering, mer aktiverade under föreställda excentriska kontraktioner. Detta aktiveringsmönster i den prefrontala barken återfanns dock endast i den icke skadade hjärnhalvan hos personer med stroke. Jämfört med kontrollgrupperna uppvisade försökspersonerna med stroke en förändrad muskelfunktion som bestod av en specifik nedsättning av styrkan under koncentriska kontraktioner samt också ett mer avvikande samband mellan styrka och ledvinkel under koncentriska kontraktioner. Den relativa belastningen under utförandet av en styrketräningsövning med en intensitet på 10RM var på grund av dessa avvikelser lägre för försökspersoner med stroke. Hjärnavbildnings-studierna indikerade att ventrolaterala prefrontala barken verkar vara involverat i ett kortikalt moduleringssystem som reglerar muskel-aktivering olika beroende på kontraktionstyp under maximala kontraktioner. Detta skulle kunna vara en underliggande mekanism bakom den hittills obesvarade frågan varför det är omöjligt att aktivera muskulaturen maximalt under excentriska kontraktioner. En störning av detta moduleringssystem hos personer med stroke verkar också kunna ligga bakom den förändrade regleringen av muskelaktivering som visat sig förekomma hos personer med stroke. Neuromuskulär funktion efter stroke är förändrad i flera avseenden vilket verkar medföra att muskulaturen inte belastas optimalt under konventionell styrketräning. Detta kan vara en delförklaring till varför styrkeökningen som svar på träning ofta är liten hos personer med stroke.
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Mayhew, Thomas Philip. "THE EFFECTS OF CONCENTRIC AND ECCENTRIC CONTRACTIONS PERFORMED AT EQUAL POWER LEVELS ON SKELETAL MUSCLE FIBER HYPERTROPHY." VCU Scholars Compass, 1991. https://scholarscompass.vcu.edu/etd/5228.
Full textAbstract:
There are no data available as to whether training with eccentric contractions are more effective than concentric contractions for producing skeletal muscle fiber hypertrophy. To better understand the effects of training with different contraction types two related studies were performed.
In the first study a device which is frequently used by clinicians for concentric and eccentric exercise, the Kin-ComR, was tested for accuracy and reliability. The measurements obtained from the force, angle, and speed transducers of this device were found to be accurate and reliable between days.
The purpose of the second study was to determine if there was a difference in the percent change of fiber area in the vastus lateralis muscle as a result of concentric and eccentric exercise at equal power levels. Twenty normal subjects were randomly assigned to two groups. Both groups exercised three times per week for four weeks on the Kin-Com dynamometer. One group performed concentric contractions of their right quadriceps femoris muscle at an intensity of 90% of their maximal concentric power through a range of 75° of knee extension. The other group performed eccentric contractions at the same relative power level. Needle muscle biopsies were obtained from the vastus lateralis muscle before and after the exercise program. Muscle fiber type differentiation was performed using a myosin adenosine triphosphatase stain at an alkaline preincubation. The percent change in fiber area was determined for each fiber type for each subject and a one-way ANOVA was used to analyze the data. Our results showed that the type II fibers of the concentric group exhibited a greater percent increase in area as compared to the eccentric group. The percent change in isometric torque was determined for each subject and a one-way ANOVA was performed on the data. The results showed that the concentric group increased maximal isometric torque production more than the eccentric group. Our results indicate that when exercising at the same relative power level a subject performing concentric contractions will 1) show greater muscle hypertrophy and, 2) improve in isometric torque production more than a subject training with eccentric contractions.
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Balshaw, Thomas G. "Acute neuromuscular, kinetic, and kinematic responses to accentuated eccentric load resistance exercise." Thesis, University of Stirling, 2013. http://hdl.handle.net/1893/17174.
Full textAbstract:
Neurological and morphological adaptations are responsible for the increases in strength that occur following the completion of resistance exercise training interventions. There are a number of benefits that can occur as a result of completing resistance exercise training interventions, these include: (i) reduced risk of developing metabolic health issues; (ii) decreased risk and incidence of falling; (iii) improved cardiovascular health; (iv) elevated mobility; (v) enhanced athletic performance; and (vi) injury prevention. Traditional resistance exercise (constant load resistance exercise (CL)) involves equally loaded eccentric and concentric phases, performed in an alternating manner. However, eccentric muscle actions have unique physiological characteristics, namely greater force production capacity and lower energy requirements, compared to concentric actions. These characteristics have led to the exploration of eccentric-focused resistance exercise for the purposes of injury prevention, rehabilitation, and enhancement of functional capacity. Accentuated eccentric load resistance exercise (AEL) is one form of eccentric-focused resistance exercise. This type of resistance exercise involves a heavier absolute external eccentric phase load than during the subsequent concentric portion of a repetition. Existing training study interventions comparing AEL to CL have demonstrated enhancements in concentric, eccentric, and isometric strength with AEL. However, no differences in strength adaptations have been reported in other AEL vs. CL training studies. Only 7 d intensified AEL training interventions have measured neuromuscular variables, providing evidence that enhanced neuromuscular adaptations may occur when AEL is compared to CL. Therefore, a lack of information is currently available regarding how AEL may differentially affect neuromuscular control when compared to CL. Furthermore, the equivocal findings regarding the efficacy of AEL make it difficult for exercise professionals to decide if they should employ AEL with their athletes or patients and during which training phase this type of resistance exercise could be implemented. Therefore, the aims of this thesis were: (i) to examine differences in acute neuromuscular, kinetic, and kinematic responses between AEL and CL during both lower-body single-joint resistance exercise and multiple-joint free weight resistance exercise; (ii) to assess acute force production and contractile characteristics following AEL and CL conditions; (iii) to investigate the influence of eccentric phase velocity (and time under tension) on acute force production and contractile characteristics following AEL and CL conditions; and (iv) to compare common drive and motor unit firing rate responses after single- and multiple-joint AEL and CL. Before investigating neuromuscular, kinetic, and kinematic responses to AEL it was deemed necessary to evaluate normalisation methods for a multiple-joint free weight resistance exercise that would permit the implementation of AEL. Therefore, the aim of the first study of the thesis was to evaluate voluntary maximal (dynamometer- and isometric squat-based) isometric and submaximal dynamic (60%, 70%, and 80% of three repetition maximum) electromyography (EMG) normalisation methods for the back squat resistance exercise. The absolute reliability (limits of agreement and coefficient of variation), relative reliability (intraclass correlation coefficient), and sensitivity of each method was assessed. Strength-trained males completed four testing sessions on separate days, the final three test days were used to evaluate the different normalisation methods. Overall, dynamic normalisation methods demonstrated better absolute reliability and sensitivity for reporting vastus lateralis and biceps femoris EMG compared to maximal isometric methods. Following the methodological study conducted in Chapter 2, the next study began to address the main aims of the thesis. The purpose of the third chapter of the thesis was to compare acute neuromuscular, kinetic, and kinematic responses between single-joint AEL and CL knee extension efforts that included two different eccentric phase velocities. Ten males who were completing recreational resistance exercise attended four experimental test day sessions where knee extension repetitions (AEL or CL) were performed at two different eccentric phase velocities (2 or 4 s). Elevated vastus lateralis eccentric neuromuscular activation was observed in both AEL conditions (p= 0.004, f= 5.73). No differences between conditions were detected for concentric neuromuscular or concentric kinematic variables during knee extension efforts. Similarly, no differences in after-intervention rate of torque development or contractile charactersitics were observed between conditions. To extend the findings of the third chapter of the thesis and provide mechanistic information regarding how AEL may differentially effect acute neuromuscular variables that have been reported to be undergo chronic adaptations, additional measures that were taken before and after the intervention described in the previous chapter were analysed. Therefore, the purpose of the fourth chapter of the thesis was to compare motor unit firing rate and common drive responses following single-joint AEL and CL knee extension efforts during a submaximal isometric knee extension trapezoid force trace effort. In addition, motor unit firing rate reliability during the before-intervention trapezoid force trace efforts was assessed. No differences in the maximum number of detected motor units were observed between conditions. A condition-time-point interaction effect (p= 0.025, f= 3.65) for firing rate in later-recruited motor units occurred, with a decrease in firing rate observed in after-intervention measures in the AEL condition that was completed with a shorter duration eccentric phase. However, no differences in common drive were detected from before- to after-intervention measures in any of the conditions. The time period toward the end of the plateau phase of before-intervention trapezoid force trace efforts displayed the greatest absolute and relative reliability and was therefore used for motor unit firing rate and common drive analysis. The purpose of the fifth chapter was to compare acute neuromuscular and kinetic responses between multiple-joint AEL and CL back squats. Strength-trained males completed two experimental test day sessions where back squat repetitions (AEL or CL) were performed. Neuromuscular and kinetic responses were measured during each condition. No differences in concentric neuromuscular or concentric kinetic variables during back squat repetitions were detected between conditions. Elevated eccentric phase neuromuscular activation was observed during the AEL compared to the CL condition in two to three of the four sets performed for the following lower-body muscles: (i) vastus lateralis (p< 0.001, f= 15.58); (ii) vastus medialis (p< 0.001, f= 10.77); (iii) biceps femoris (p= 0.003, f= 6.10); and (iv) gluteus maximus (p= 0.001, f= 7.98). There were no clear differences in terms of the neuromuscular activation contributions between muscles within AEL or CL conditions during eccentric or concentric muscle actions. Following the investigation of acute motor unit firing rate and common drive responses to lower limb single-joint AEL and CL in the fourth chapter of the thesis, the question arose as to whether or not similar responses would occur in a more complex model, such as a multiple-joint resistance exercise. Multiple-joint resistance exercise poses different neuromuscular activation, coordination, and stabilisation demands. Therefore, the purpose of the sixth chapter of the thesis was to compare acute motor unit firing rate and common drive responses following multiple-joint lower-body free weight AEL and CL.
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Yang, Li. "Behaviour of masonry columns of geometric section subjected to eccentric axial load." Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705160.
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Niesen-Vertommen, Sherri. "The effect of an eccentric-type exercise versus a concentric-type exercise in the management of chronic Achilles tendonitis." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/28144.
Full textAbstract:
The main purpose of this study was to determine which method of tendon rehabilitation - the "eccentric ankle drop" exercise or the universal gym "concentric plantarflexion/dorsiflexion" exercise - produced a more effective result in terms of recovery in the treatment of chronic Achilles tendonitis.
Seventeen subjects with chronic Achilles tendonitis were studied. They were selected on the basis that they had a history of athletic participation, and have had the symptoms of Achilles tendonitis greater than three weeks.
Subjects were assigned to either of two groups: training using the "eccentric ankle drop" exercise or training using the "concentric plantarflexion/ dorsiflexion" exercise. Subjects were clinically examined by a physician and referred to the study, then placed on a twelve week exercise program. They were examined and tested at 0, 4, 8 and 12 weeks. Testing included the following variables: average and peak torque measured on the KIN/COM Isokinetic Dynamometer at 3 0 and 50 degrees per second, and for plantarflexor concentric and eccentric muscle contractions, a subjective evaluation of pain and return to activity rated on a scale from 1 to 10.
The results showed the "eccentric ankle drop" exercise did not significantly increase in average or peak torque values at either velocity of 3 0 or 50 degrees per second more so than the "concentric plantarflexion/dorsiflexion" exercise. However, the eccentric group did demonstrate larger gains in both torque value compared to the concentric group. The plantarflexor torque values on the whole increased in a linear fashion at both velocities for both groups similarly, as indicated by the highly significant trend analysis (p<.001). There was a significant difference seen in pain ratings between the groups averaged over the four testing sessions (p<.01) with the eccentric group decreasing in pain more than the concentric group. Also, the eccentric exercise group produced three times as many "pain free" subjects at the end of the program than the concentric group. There was not a significant difference observed between the eccentric exercise group and the concentric exercise group with the return to activity effect. However the eccentric group over the twelve week period demonstrated a quicker return to preinjury activity than did the concentric group. The eccentric group also produced four times as many full return to preinjury activity level subjects by the end of the program than did the concentric group. Also the return to activity effect increased in a linear fashion for both groups similarly, as indicated by the highly significant trend analysis (P<.001).
Although no statistical significance was found between the two exercise groups (except for pain levels), the subjective measures favor the use of the eccentric exercise. Thus from a clinical standpoint, the eccentric exercise can be recommended as a more positive approach toward the conservative management of chronic Achilles tendonitis.Education, Faculty of
Curriculum and Pedagogy (EDCP), Department of
Graduate
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ARAUJO, JOSÉ HENRIQUE CARNEIRO DE. "NUMERICAL SIMULATIONS VIA FINITE ELEMENT OF VISCOUS FLOW BETWEEN CONCENTRIC AND ECCENTRIC CYLINDERS WITH ROTATING INNER AND VARIABLE VISCOSITY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1987. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19059@1.
Full textAbstract:
COMISSÃO NACIONAL DE ENERGIA NUCLEAREfetuou-se um estudo numérico do escoamento entre cilindros concêntricos e excêntricos girantes com efeitos de dissipação viscosa presente. Assumiu-se que o cilindro interno estava girando com uma velocidade angular constante e que o externo estava fixo. Assumimos a condição de contorno de não deslizamento para velocidade em ambas as paredes. A temperatura do fluido nas paredes dos cilindros foi assumida constante e seu campo assumimos ser governado por efeitos de convecção e condução, com uma fonte de energia proveniente da dissipação viscosa do escoamento. A viscosidade do fluido foi assumida variável com a temperatura. A discretização espacial foi feita por elementos finitos através de funções de base lineares, mais uma função estabilizadora para velocidade no caso dos cilindros excêntricos. O método das características foi usado no problema excêntrico. Resultados computacionais ilustram a eficiência da técnica adotada.
A computational study of viscous flow between concentric and eccentrically rotating cylinders in presented in which the effect of viscous dissipation is taken into account. The inner cylinder is assumed to be rotating at constant speed with respect to the outer one. We assume a no-alip boundary condition for the velocity on both walls. The temperature of the fluid is assumed to be constant on the cylinders and its distribution is assumed to be governed by both conduction and convection, with a supplementary soure of energy du to the effects of viscous dissipation. The viscosity is assumed to be varies with temperature. The space discretization is based on piecewise linear finite elements, with velocity stabilization in case of the eccentrically cylinders. The method of characteristics is used for time integration in the eccentrically problem. Numerical results illustrate the efficienty of the adopted approach.
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Vejarano, Maria Eugenia. "Effect of a non-steroidal, anti-inflammatory drug (Indocin) on selected parameters of muscular function following concentric and eccentric work." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45648.
Full textAbstract:
Evidence from various studies indicates that eccentric contractions produce more post-exercise changes in muscular function than do concentric contractions. Delayed muscular soreness, the pain and tenderness present 1 or 2 days after exercise, is negatively correlated with muscular performance and occurs particularly after eccentric work. The action of an analgesic, anti-inflammatory drug (Indocin) on muscular soreness indicates it may be effective in accelerating recovery of muscle function after eccentric work.
In the study reported herein the effects of Indocin on muscular performance, as evaluated on the Cybex II isokinetic dynamometer, following prolonged concentric and eccentric work, were evaluated in 48 subjects who were randomly assigned to one of four drug groups. Subjects performed a 30 minute step test during which one limb led the stepping movement throughout (concentric contractions) and the contralateral limb trailed throughout (eccentric contractions). The muscular performance parameters of peak torque (PT), torque acceleration energy (TAE) and average power (AVP), evaluated at slow and high velocities, andthe range of motion (ROM) at the knee joint were assessed prior to the step test and at five intervals thereafter. A nonâ significant decrease in PT and TAE at the contraction speed of 60 deg/sec were present in the eccentric limbs, greater reductions evidenced in the placebo group. Non-significant changes occured in the concentric limbs, Non-significant changes in ROM and in muscular function parameters evaluated at 250 deg/sec were observed.
Master of Science
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Quinlan, Jonathan. "Structural and mechanical responses to concentric and eccentric functional overloading of the 'Muscle-Tendon Unit' in young and older individuals." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49092/.
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Bernat, Masó Ernest. "Analysis of unreinforced and TRM-strengthened brick masonry walls subjected to eccentric axial load." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/145389.
Full textAbstract:
A significant number of buildings are supported by load-bearing masonry walls. The preservation of these worldwide used structures is a sustainable alternative. However, there is little research about the structural response of these particular elements if compared with others like concrete or steels framed structures. Hence, a further study of the load-bearing masonry walls is necessary as a starting point for the preservation activities.
The load-bearing masonry walls are usually subjected to a vertical eccentric loading condition, which is related with their complex structural response. This response is characterised by the second-order bending effects due to the eccentricity of the load, the non-linear compressive response of the masonry and its almost negligible tensile strength. Thus, strengthening these walls, in order to increase their load-bearing capacity, is an interesting upgrading alternative to enhance their life-cycle.
In this thesis, an experimental campaign has been carried out. It consisted of hundreds of characterisation tests to obtain the mechanical properties of the component materials which have been used to build twenty-nine full-scale walls. Twenty of these walls were unreinforced and the other nine were TRM (Textile Reinforced Mortar) strengthened. All of them have been tested under eccentric compressive loading conditions. The analysis of the strengthened walls has allowed studying the influence of the strengthening mortar type on the load-bearing capacity. The effects using anchors or embedding different types of fibre grids have been also analysed.
A bidimensional (2D) simplified micro-model has been implemented to analyse these structural cases. This numerical tool has been validated using the data from the experimental campaign. Finally, analytical methodologies have been proposed to calculate the load-bearing capacity of unreinforced and TRM-strengthened brick masonry walls. Similarly, two current standards, Eurocode-6 and ACI-530 have been applied to the analysed cases and their results have been compared with the experimental ones.
The results show that the TRM provides a load-bearing capacity increase over 100% and homogenises the structural response, which becomes stiffer. Regarding the simulations, the proposed numerical model provides accurate results, which are better for the cases with larger slenderness or larger eccentricity of the applied load. Finally, the proposed analytical methods provide acceptable results, which are more accurate than the ones obtained by applying the formulations included in the analysed standards.Un nombre significant d'edificis estan suportats per murs de càrrega d'obra de fàbrica. La preservació d’aquestes estructures que s’utilitzen arreu del món is una alternativa sostenible. No obstant això, hi ha molt poca recerca en relació a la resposta estructural d’aquests elements particulars si es compara amb altres com les estructures porticades d’acer o formigó. Per tant, és necessari un major estudi dels murs de càrrega d’obra de fàbrica com a punt de partida de les actuacions de preservació. Normalment, els murs de càrrega estan subjectes a patrons de càrrega vertical excèntrica, cosa que està relacionada amb la seva resposta estructural complexa. Aquesta resposta es caracteritza pels efectes de flexió de segon ordre degut a l’excentricitat de la càrrega, per la resposta no linear a compressió de l’obra de fàbrica i per la seva, pràcticament negligible, resistència a tracció. Per tant, el reforç d’aquests murs, per tal d’augmentar-ne la seva capacitat resistent is una alternativa de millora interessant per allargar la seva vida útil. En aquesta tesi s’ha dut a terme una campanya experimental. Aquesta ha consistit en centenars d’assaigs de caracterització de les propietats mecàniques dels materials components utilitzats per construir vint-i-nou murs. Nou d’aquests es van reforçar amb Textile Reinforced Mortar, TRM, i els altres vint van ser assajats sense reforç. Tots van ser sotmesos a compressió excèntrica. L’estudi dels murs reforçats ha permès analitzar la influència del tipus de morter de reforç, l’efecte de disposar ancoratges o la dependència de la capacitat resistent en el tipus de malla de fibra utilitzada. S’ha implementat un micromodel simplificat bidimensional (2D) per analitzar els casos estructurals proposats. Aquesta eina numèrica ha estat validada utilitzant les dades de la campanya experimental. Finalment, s’han proposat mètodes analítics per calcular la capacitat portant dels murs sense reforç i dels reforçats amb TRM. De forma semblant, s’han aplicat dos normes actuals, l’Eurocodi-6 i l’ACI-530, als casos d’estudi per tal de comparar-ne els resultats amb els experimentals. Els resultats mostren que el TRM aporta un augment de la capacitat resistent de més del 100% i homogeneïtza la resposta estructural que esdevé més rígida. En relació a les simulacions, el model numèric proposat obté resultats acurats, els quals són millors pels casos de major esveltesa o més excentricitat de la càrrega. Per acabar, els mètodes analítics que es proposen aporten resultats acceptables, els quals s’ajusten millor als experimentals que els obtinguts aplicant les formulacions de les normatives.
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Baranauskienė, Neringa. "The residual effect of eccentric concentric prior exercise on pulmonary gas exchange and muscle electrical activity during cycling of different intensity." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2013~D_20131014_105852-02810.
Full textAbstract:
It is well established that unaccustomed eccentric concentric exercise evokes delayed onset muscle soreness (DOMS) (MacIntyre et al., 2001; Dannecker et al., 2005, 2008; Fredsted et al., 2008; Lewis et al., 2012), muscle fibre disarrangement (Hortobagyi et., al., 1998; Stupka et al., 2001; Carlsson et al., 2007), inflammatory cell emission into blood (Stupka et al., 2001; Laaksonen et al., 2006), increase of the activity of blood plasma creatinkinasis (Stupka et al., 2000; Chen et al., 2010; Skurvydas et al., 2010), decrease of muscle force production (Chen et al., 2010; Semmler et al., 2007; Skurvydas et al., 2010) and decrease of aerobic work capacity (Black, Dobson, 2012). The aforementioned functional, sensory, biochemical and structural changes independently from each other are displayed immediately after eccentric exercise and stay for up to 7 days, dependence on the level of damage (Clarkson et al., 1992; Skurvydas et al., 2000; Stupka et al., 2000, 2001; MacIntyre, 2001; Totsuka et al., 2002; Nottle, Nosaka, 2007; Tofas et al., 2008; Lewis et al., 2012; Paulsen et al., 2012).
It is still not clear what acute and residual effect of eccentric exercise on the pulmonary gas exchange is had during different intensity work. It was determined that one hour after eccentric concentric exercise, there increases absolute VO2 during moderate (Zaičenkovienė, Stasiulis, 2010) and heavy intensity loads (Ratkevičius et al., 2006). 48 hours after eccentric exercise, when the... [to full text]Atlikta daug tyrimų, kuriais nustatyta, kad neįprasti ekscentriniai koncentriniai fiziniai pratimai sukelia vėluojantį raumenų skausmą (MacIntyre et al., 2001; Dannecker et al., 2005, 2008; Fredsted et al., 2008; Lewis et al., 2012), raumeninių skaidulų pažaidą (Hortobagyi et al., 1998; Stupka et al., 2001; Carlsson et al., 2007), uždegiminių ląstelių išskyrimą į kraują (Stupka et al., 2001; Laaksonen et al., 2006), kraujo plazmos kreatinkinazės aktyvumo padidėjimą (Stupka et al., 2000; Chen et al., 2010; Skurvydas et al., 2010), raumenų jėgos sumažėjimą (Chen et al., 2010; Semmler et al., 2007; Skurvydas et al., 2010) bei aerobinio darbo galingumo sumažėjimą (Black, Dobson, 2012). Minėti funkciniai, sensoriniai, biocheminiai ir struktūriniai pakitimai nepriklausomai vienas nuo kito pasireiškia iš karto po ekscentrinių krūvių ir išlieka iki 7 parų, priklausomai nuo pažaidos dydžio (Clarkson et al., 1992; Skurvydas et al., 2000; Stupka et al., 2000, 2001; MacIntyre, 2001; Totsuka et al., 2002; Nottle, Nosaka, 2007; Tofas et al., 2008; Lewis et al., 2012; Paulsen et al., 2012). Vis dar nėra aišku, koks yra ūminis ir liekamasis ekscentrinio krūvio poveikis kvėpavimo dujų apykaitos rodiklių kaitai įvairaus intensyvumo darbo metu. Nustatyta, kad, praėjus vienai valandai po ekscentrinio koncentrinio krūvio, padidėjo absoliučios VO2 reikšmės vidutinio (Zaičenkovienė, Stasiulis, 2010) ir didelio intensyvumo krūvių metu (Ratkevičius et al., 2006). Praėjus 48 val. po ekscentrinio... [toliau žr. visą tekstą]
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Silal, Sandhya Prakash. "A randomised control trial for the restoration of functional ability in patients post total knee arthroplasty: Eccentric versus concentric cycling ergometry." Master's thesis, Faculty of Health Sciences, 2018. http://hdl.handle.net/11427/30804.
Full textAbstract:
Introduction: While the total knee arthroplasty procedure improves joint-specific outcomes, including pain and range of movement, functional deficits post-surgery has been noted. Movement abnormalities and quadriceps weakness of the operated limb, as well as a decrease in strength on the non-operated have been widely reported. Recovery of strength and function to normal levels is also rare, thereby predisposing patients to future disability with increasing age. The purpose of this study was to determine the effects of an eight-week eccentric cycling ergometry exercise intervention versus a concentric cycling ergometry exercise intervention in total knee arthroplasty recipients three to nine months post-surgery. This study aimed to a) investigate the change in joint kinetics, kinematics and muscle activity during the phases of gait, between the eccentric and concentric groups over time and b) To determine if an eccentric cycling exercise intervention produces greater improvements in knee function when compared to concentric cycling exercise. Methods: Eighteen participants, three to nine months post total knee arthroplasty were recruited and randomly assigned to either an eccentric or concentric cycling exercise intervention group. Participants performed three exercise sessions weekly over a progressive eight-week period on the Grucox Isokinetic Ergometer. Walking gait analyses and functional outcomes, as measured by the six-minute walk test and validated knee scores (Knee Injury and Osteoarthritis Outcome Score, SF-36 Health Survey and Tegner Activity Scale) were recorded pre- and post-intervention. Results: The concentric group knee flexion range of movement increased significantly during the swing phase of gait (p=0.021) post-intervention together with a significant increase in the peak knee flexion angle during swing (p=0.038). The concentric group showed significant differences between pre and post-rehabilitation in knee flexion range of movement during the swing phase of gait (p=0.030). Significant correlations between knee joint stiffness and the quadriceps:hamstring co-activation ratio were observed in the concentric intervention group pre-intervention: during the pre-activation phase of gait between knee joint stiffness and vastus medialis / biceps femoris (r=-0.68; p=0.042) and during load acceptance phase of gait between knee joint stiffness and vastus lateralis / biceps femoris (r=0.07; p=0.036). The eccentric group recorded neuromuscular changes post-intervention with a significant decrease in the muscle activity of the biceps femoris during load acceptance phase of gait (p=0.021). The eccentric group had significantly better functional outcomes in the overall score of Knee injury and Osteoarthritis Outcome post-intervention (p=0.008) with a significant increase in function seen in the Sports and Recreation subgroup (p=0.008) and a significant increase in the level of activity as measure by the Tegner Activity Scale post-intervention (p=0.028), despite not showing any significant changes in the knee joint kinetics and kinematics. The concentric group only reported a significant increase in the overall score of the of the SF-36 Health Survey (p=0.011) with significant increases in three of the subgroups post-intervention: Bodily pains had improved (p=0.042), the role limitations due to physical heath had improved (p=0.028) and the role limitations due to emotional health had also improved (p=0.009). The concentric group also showed significant improvement in the emotional health over the intervention in comparison to the eccentric intervention group (p=0.020). Both intervention groups reported a similar significant increase in the distance covered during the six-minute walk test post-intervention (p=0.038). Conclusion: The results of this exploratory study did not find the eccentric cycling rehabilitation intervention exclusively more effective than the concentric cycling intervention in the restoration of functional ability in patients post-TKA. The eccentric intervention did however result in neuromuscular adaptations consistent with a move towards a more typical asymptomatic gait pattern and participants reported greater functional improvements on validated knee functional assessments and levels of activity scores. The concentric intervention yielded kinematic changes and participants reported improvements in their emotional and physical health post-intervention. Eccentric training and its role in early stage post-operative rehabilitation is limited. Based on the findings from this exploratory study, the benefit of eccentric training as an adjunct to rehabilitation and its role in contributing to greater improvements in the restoration of functional ability post-TKA needs to be further explored.
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Ameen, Syed Fakhrul. "Strip footing on a sand layer overlying a rigid stratum and subject to inclined eccentric loads." Thesis, University of Strathclyde, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293221.
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Bakkum, Amanda. "A randomised control trial for the restoration of functional ability in patients post total knee arthroplasty: a comparison of eccentric versus concentric cycling ergometry." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/16477.
Full textAbstract:
Includes bibliographical referencesPurpose: The predominant impairment to function following a total knee arthroplasty (TKA) is a distinctive reduction in quadriceps muscle strength. It has been suggested that eccentric rehabilitation may be more beneficial than traditional concentric only rehabilitation at improving muscle strength, physical functioning and quality of life in this population. The aim of this study was therefore to determine if an eccentric cycling ergometry rehabilitation intervention (a) was feasible in participant's early after TKA surgery (Study 1), (b) resulted in greater improvements in muscle strength and endurance, as well as muscle activity and muscle volume (Study 2) and, (c)resulted in greater knee functional ability, health related quality of life and physical activity levels (Study 3), when compared to an concentric cycling ergometry rehabilitation intervention. Finally, knee and hip kinematics, ground reaction force and muscle activity was described during the sit-to-stand transfer within this population (Study 4). Methods: Eighteen age- and sex-matched participants', three to nine month's post-TKA were recruited and randomly divided into either an eccentric or concentric cycling rehabilitation intervention. The participants were required to perform three exercise sessions a week, over a period of eight weeks. Isokinetic strength and muscle activity of the quadriceps and hamstring muscles, sit-to-stand motion capture analysis and knee functional ability and health related quality of life questionnaires (Knee Injury and Osteoarthritis Outcome Score, SF-36Health Survey and Tegner Activity Scale) were assessed pre and post- rehabilitation intervention. Data Analysis: Two-way repeated-measures analysis of variance were used to analyse the effects of time and the ECC and CON intervention groups and the group/time interaction for each of the dependent variables. Results: The eccentric rehabilitation intervention was well tolerated with regards to pain levels in participants' as early as three months post-TKA, the peak level of pain perceived per session, never exceeding a "mild" classification. The eccentric intervention resulted in greater power (P= 0.029) and work output (P ≤ 0.001) with a reduced overall heart rate (P= 0.014) ; moderate decreases in biceps femoris (BF) muscle activity (-3.2%) and increases in the lean thigh volume (+807.32) of the uninvolved limb; as well as improvements in the physical fun ctioning (+12.2%) and physical role functioning SF-36 scores (+22.2%) and the level of physical activity (+0.9) (Tegner activity scale). The concentric intervention resulted in decreases in vastus lateralis (VL) muscle activity (-8.17%) and work fatigue (-7.34%) and increases in the lean thigh volume (+677.49) and the hip abduction angle (+ 2.67°) (sit-to-stand) of the involved limb. Conclusion: The eccentric rehabilitation intervention is well tolerated with regards to pain and is characterised by significantly greater power output produced and work performed at significantly lower heart rates. Eccentric cycling ergometry matched in perceived exertion and duration, is associated with greater improvements in physical functioning outcome scores, physical activity level and knee flexion muscle efficiency during concentric contractions, when compared with concentric cycling ergometry. However, knee extensor muscle endurance and efficiency during concentric contractions, as well as muscle volume of the involved limb increased more significantly after concentric training in comparison to eccentric training, Further research is required to establish which training modality is the most feasible and effective in restoring knee function in participant's three months post-TKA.
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Lagemann, Frederico. "Estudo da representação numérica do comportamento mecânico de músculos esqueléticos sujeitos à combinação de diferentes tipos de contrações." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/131057.
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Esta dissertação apresenta um estudo da caracterização numérica do comportamento mecânico de um músculo esquelético estriado sujeito à combinação de diferentes contrações. A partir dos mecânismos fisiológicos da contração do tecido muscular esquelético, são apresentadas as principais características da produção de força do músculo em diferentes tipos de contrações (isométrica, concêntrica, excêntrica) e suas combinações. A representação numérica da resposta mecânica do músculo esquelético foi investigada por diferentes autores. Dos diversos modelos encontrados na literatura, alguns foram escolhidos para a continuidade deste estudo, segundo sua capacidade representativa e facilidade de implementação em métodos numéricos de solução para grandes deformações. Os modelos disponíveis na literatura foram implementados e avaliados para diferentes sequências de contrações, sendo também realizado um ajuste de parâmetros para dados experimentais de contrações isométricas e isométricas-excêntricas-isométricas. Nenhuma das propostas avaliadas apresentou resultados satisfatórios. A principal deficiência dos modelos foi a incapacidade de reproduzir a dependência do histórico de carregamentos, ou seja, da combinação de contrações. Desta maneira, uma nova proposta de modelo constitutivo foi desenvolvida e implementada para testes uniaxiais e em um código de elementos finitos para testes tridimensionais. A partir destas implementações, foram executados testes numéricos para diferentes sequências de contrações, avaliando a capacidade representativa do modelo proposto neste trabalho. O modelo proposto apresentou bons resultados para contrações isométricas e a combinação de contrações com diferentes níveis de alongamento, ou encurtamento, a uma mesma velocidade. A principal contribuição deste modelo é a capacidade de representar a resposta associada à fadiga muscular e o ganho, ou perda de força, observados experimentalmente.This work present a striated skeletal muscle numerical characterization subjected to different contractions. From the physiological contraction mechanism of the skeletal muscle tissue the force produced in different kinds of contraction (isometric, concentric and eccentric), and their combination, are presented. The numerical representation of these response was investigated by different authors. From the diverse models found in literature, some were selected to be studied according to their representation capability and the implementation ease in numerical methods for large strains. The models available in literature were implemented and evaluated for different contractions combinations and a parameter identification for experimental results of two isometric contraction and a isometric-eccentric-isometric contraction. None of the proposed models presented satisfactory results. The main deficiency of these models were the incapability of reproducing the loading history dependence, in other words, the contraction combination. In this way, a new material model was proposed and implemented to uniaxial and tridimensional finite element method tests. From these, different contractions sequences evaluated the proposed model representation capabilities. The proposed model present good results to isometric contraction, as well as contraction combination with different stretch, or shortening, level in the same speed. The main contribution of this model is the capability of represent the the response associated to the muscle fatigue and the force gain or loss, experimentally observed.
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Jonaitytė, Kristina. "Liekamasis ekscentrinio krūvio poveikis vegetacinių rodiklių kaitai didelio intensyvumo darbe." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050518_090359-23929.
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The hypothesis. We supposed the fatigue and its residual phenomena generated by eccentric load to have effect on the changes in vegetative indices, the slow component during exercise of high aerobic intensity in particular.
The aim of the research was to establish the residual effect of eccentric load on the changes in vegetative indices during exercise of high intensity.
The tasks set were as follows: 1. To estimate the residual effect of eccentric load on the fast component of changes in vegetative indices during exercise of high intensity. 2. To estimate the residual effect of eccentric load on the slow component of changes in vegetative indices during exercise of high intensity.
The subjects were 8 students of the Lithuanian University of Agriculture, members of the university basketball team, who gave their informed consent to take part in the experiments within the present study. The age of the subjects was 19,5 ± 0,53 years, height – 191,0 ± 5,8 cm and body mass – 86,5 ± 9,78 kg respectively.
The methods used were as follows: changes in the values of VO2, VCO2, heart rate (HR) and Ve indices of the subjects were established applying the test of continuously increased load and the test of constant load when pedalling the veloergometer. After testing blood of the subjects to establish lactate concentration in the blood was taken. To evaluate the level of intensity of the exercise performed by the subjects the evaluation scale of perceptible efforts (intensity of... [to full text]
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Worcester, Katherine Sara. "EFFECTS OF INERTIAL LOAD ON SAGITTAL PLANE KINEMATICS DURING FLYWHEEL-BASED RESISTANCE TRAINING SQUATS." UKnowledge, 2018. https://uknowledge.uky.edu/khp_etds/57.
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Background: Training to increase muscular power is essential for improving athletic performance in most sports. Weight training (WT) is a common means for training muscular power. Another modality, flywheel resistance training (FRT), may be superior for improving muscular power. However, few studies have examined if FRT is kinematically similar to WT, or if FRT kinematics change with increasing inertial load. The purposes of this study were to determine how sagittal plane joint kinematics are affected by increasing inertial load during FRT squats, and to determine how FRT squat joint kinematics compare to WT squat joint kinematics.
Methods: Subjects (n=9) completed three visits for this study. On the first visit subjects completed squat 1 repetition maximum (1RM) testing. The second visit served as a full FRT familiarization session in which subjects performed one set of 5 maximal effort FRT squats at each inertial load (0.050, 0.075, and 0.100 kgm2). On the third visit, subjects were videoed in the sagittal plane while performing the FRT squat protocol. Subjects then completed 5 maximal velocity repetitions of WT squats with the barbell loaded according to the Kansas Squat Test (KST) protocol. Kinematic differences between inertial loads were determined via 1-way repeated measures ANOVAS while differences between FRT and WT were determined with paired T-tests.
Results: There were no differences in peak sagittal plane knee, trunk-hip, trunk (absolute) or ankle angles between inertial loads. Peak and mean joint angular velocities decreased with increasing inertial loads at the knee and trunk-hip. Mean joint angular velocities decreased at the ankle with increasing inertial loads, while peak and mean trunk (absolute) angular velocities were unaffected. No statistical analyses were conducted for FRT and WT comparison as not enough subjects met the criteria (n=3).
Conclusions: Sagittal plane joint kinematics are largely maintained despite increasing inertial load during FRT squats. Lower extremity joint angular velocities decreased with increasing inertial load. If training for muscular power and knee extensor velocity is the goal, then the inertia of 0.050 kgm2 is most suitable.
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Divljak, Gordan. "Acute effect of continuous running or cycling exercise on subsequent strength performance : A Concurrent training study." Thesis, Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:gih:diva-4526.
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Aim Aerobic exercise may interfere with subsequent responses to strength training. The aim of this research was to examine the acute effects of cycling or running on subsequent leg strength performance. It was hypothesized that eccentric contractions induced by running would impair strength performance more than the cycling mode of exercise, which consist mainly of concentric muscle actions. Method In order to investigate if continuous running or cycling affected following strength performance, 6 healthy individuals (5 males, 1 female) were subjected to a randomized cross-over design. Subject characteristics were age (year) 25,5 ± 2,1, height (cm) 180,5 ± 6,4, and body weight (kg) 83 ± 3,4. The experimental sessions included three protocols: strength protocol (S) which included 3 repetitions measuring peak power followed by 3 sets to muscular failure at 80% of 1RM in the squat exercise; and continuous running (RS) and cycling (CS) conditions (40 minutes at 80% of maximal heart rate), followed by the S protocol. Peak power performance and total work volume was measured. Results Average peak power attained between the three protocols were CS = 1639± 444Watts (W), RS = 1633± 422 and S = 1565 ± 349. No significant differences were observed between the three conditions (P = 0,817). No differences across the three protocols was observed for highest peak power attained by each subject (P = 0,619). Total work volume performed (main effect P = 0,027) revealed a significant difference between CS = 2559 kg and S = 3715 kg (P=0,037), and CS and RS = 3345 kg (P=0,037) due to the lower loads lifted in CS. Conclusions There were no differences observed between the three training protocols regarding peak power performance. When cycling exercise was performed prior to the strength session, the total volume lifted was lower than when performing the strength test alone. Thus, it is concluded that cycling exercise, but not running, interferes with subsequent strength training performance.Syfte och frågeställningar Uthållighetsträning kan leda till försämrad styrkeprestation. Syftet med denna forskning var att undersöka de akuta effekterna från cykling eller löpning på efterföljande benstyrka. Hypotesen var att löpning, som omfattar excentriska muskelaktioner, skulle leda till en större försämring av efterföljande styrkeprestation jämfört med cyking, som främst omfattar koncentriska muskelaktioner. Metod För att undersöka om kontinuerlig cykling och löpning påverkade efterföljande benprestation, undersöktes 6 deltagare (5 män, 1 kvinna) i en randomiserad cross-over design. Försökspersonernas karakteristika var ålder (år) 25,5 ± 2,1, längd (cm) 180,5 ± 6,4, vikt (kg) 83 ± 3,4. Försökspersonerna utförde tre experimentella protokoll: styrka (S), vilket bestod av 3 repetitioner av maximal kraftutveckling efterföljt av 3 set till muskulär utmattning på 80% av 1RM i benböj; och löpning (RS) samt cykling (CS) protokoll (40-minuter på 80% av maximal hjärtfrekvens), efterföljt av S protokollet. Data för maximal kraftutveckling och total arbetsvolym samlades in. Resultat Den genomsnittliga maximala effekten som uppnåddes mellan de tre protokollen var: CS = 1639 ± 444 Watt (W), RS = 1633 ± 422W och S = 1565 ± 349W. Inga signifikanta skillnader observerades mellan de tre förhållandena (P=0,817). Högst uppnådda effekten för varje deltagare mellan de tre förhållandena visade ingen skillnad (P=0,619). Totala arbetsvolymen (tidseffekt: P=0,027) visade signifikanta skillnader mellan CS = 2559 kg och S = 3715 kg (P=0,037), och CS och RS = 3345 kg (P=0,037) på grund av lägre vikt lyft vid CS. Slutsats Ingen skillnad observerades mellan de tre förhållandena angående maximal styrkeprestation. Den totala vikt volymen som kunde lyftas var dock lägre när cykling utfördes innan styrketestet. Slutsatsen är därför att cykling, men inte löpning, hindrar maximal träningsprestation vid ett efterföljande styrkepass.
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Kosterina, Natalia. "Modelling of muscular force induced by non-isometric contraction." Doctoral thesis, KTH, Strukturmekanik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95418.
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The main objective of the study was to investigate and simulate skeletal muscleforce production during and after isometric contractions, active muscle lengtheningand active muscle shortening. The motivation behind this work was to improve thedominant model of muscle force generation based on the theories of Hill from 1938. Effects of residual force enhancement and force depression were observed after concentric and eccentric contractions, and also during stretch-shortening cycles. It wasshown that this force modification is not related to lengthening/shortening velocity, butinstead the steady-state force after non-isometric contractions can be well describedby an initial isometric force to which a modification is added. The modification isevaluated from the mechanical work performed by and on the muscle during lengthvariations. The time constants calculated for isometric force redevelopment appearedto be in certain relations with those for initial isometric force development, an observation which extended our basis for muscle modelling. A macroscopic muscular model consisting of a contractile element, and paralleland series elastic elements was supplemented with a history component and adoptedfor mouse soleus muscle experiments. The parameters from the experiment analysis, particularly the force modification after non-isometric contractions and the timeconstants, were reproduced by the simulations. In a step towards a general implementation, the history modification was introduced in the muscluloskeletal model ofOpenSim software, which was then used for simulations of full body movements.QC 20120525
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Mikšta, Audrius. "12–13 metų berniukų raumenų mažų dažnių nuovargis atliekant izometrinius ir ekscentrinius-koncentrinius fizinius pratimus." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2006. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2006~D_20060522_125049-48828.
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The aim of the study: to determine and compare the low frequency fatigue of the legs’ muscles of 12–13 years old boys during the isometric and eccentric-concentric physical exercises.
The objectives of the study:
1. To determine the exertion of low frequency fatigue during isometric exercises in boys.
2. To determine the exertion of low frequency fatigue during eccentric-concentric exercises in boys.
3. To compare the exertion of low frequency fatigue among isometric and eccentric-concentric exercises in boys.
Subjects. Healthy boys (n = 6) aged 12–13 (12,4 ± 0,6) who do not participate in sports regularly but attend the classes of physical education twice a week. The rest period between the studies was three weeks. The tension was set up at 50 % MVS level. After that the values of the contractions and relaxations of the muscles were registered as follows:
1. The strength of muscle contraction caused by a single electric stimulus (Pt);
2. The strength of muscle contraction (P) caused by the following regiments of electrostimulation: 7 Hz (P7), 10 Hz (P10), 15 Hz (P15), 20 Hz (P20), and 100 Hz (P100) (the duration of the stimulation – 1 s, and the rest intervals between stimulations – 5 s);
3. Maximal voluntary strength (MVS) of muscle contractions (three trials every 3 minutes);
4. The workout (10 minutes of slow pedaling on the ergometer: the heart rate contractions from 110 to 130 times per minute);
5. Isometric workload: 18 times, each lasts 15 s, 40 % MVS contraction... [to full text]
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Peterson, Magnus. "Chronic Tennis Elbow : Aspects on Pathogenesis and Treatment in a Soft Tissue Pain Condition." Doctoral thesis, Uppsala universitet, Allmänmedicin och klinisk epidemiologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160051.
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Objectives: To study the treatment practice of chronic tennis elbow (TE) among general practitioners (GPs) and physiotherapists (PTs), the effects of a simple, graded home exercise regime versus expectation, the effects of eccentric versus concentric exercise, and the involvement of the substance P – NK1 receptor system in the peripheral, painful tissue of chronic TE patients by positron emission tomography (PET). Materials and methods: A postal survey regarding therapeutic methods used in patients with chronic TE was sent to 129 GPs and 77 PTs, 81 subjects with chronic TE were randomly and blindly assigned to either an exercise group or a wait list group, 120 subjects were randomly assigned to either eccentric or concentric exercise and ten subjects were examined by PET and the NK1 specific radioligand [11C]GR205171. Results: High proportions of GPs and PTs used ergonomic counselling and stretching in the treatment of chronic TE. The majority of GPs prescribed passive anti-inflammatory measures such as sick leave and anti-inflammatory medication. Many PTs prescribed dynamic, particularly eccentric, exercise. Graded dynamic exercise according to a simple low-cost protocol, has better effect on pain than a wait-and-see attitude. Adjusted for outcome affecting variables, eccentric graded exercise has quicker effect than concentric graded exercise. During PET scan with the NK1 specific radioligand [11C]GR205171, voxel volume and signal intensity of this volume was significantly higher in the affected than the unaffected arm in subjects with unilateral chronic TE. Conclusions: GPs and PTs used many treatments to a similar extent but differed regarding the use of exercise. Chronic TE responds favourably to graded dynamic exercise aimed specifically at the painful tissue. The exercise should stress the eccentric work phase. The substance P – NK1 receptor system seems to play a part in the peripheral, painful tissue of a chronic, soft tissue pain condition such as chronic TE.Epi-X
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Mustafa, Mansoor. "Investigation into Offset Streams for Jet Noise Reduction." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437477139.
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Garnier, Yoann. "Influence des modalités de contraction musculaire sur les effets neuroplastiques de l'exercice." Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK034/document.
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Parallèlement aux adaptations cardiovasculaires et neuromusculaires, les exercices mono-articulaires ou locomoteurs peuvent induire des changements neuroplastiques de muscles impliqués ou non dans l’exercice. Si l’effet de paramètres de l’exercice, comme l’intensité ou la durée, sur les changements neuroplastiques ont déjà été étudiés, l’effet du mode de contraction musculaire reste, quant à lui, moins connu. L’objectif de cette thèse a été d’évaluer les effets du mode de contraction musculaire sur les changements neuroplastiques consécutifs à un exercice locomoteur ou mono-articulaire. La première étude a montré que l’augmentation de l’excitabilité corticospinale d’un muscle non-impliqué dans l’exercice (muscle de la main), observée suite à un exercice de marche/ course, n’était pas modulée par le mode de contraction des muscles extenseurs du genou. En revanche, une modulation spécifique des réseaux intracorticaux par le mode de contraction impliqué lors d’un exercice a été mise en évidence par l’application d’un protocole de stimulation associative jumelée. Des observations similaires ont été faites dans une seconde étude investiguant les changements corticospinaux observés au niveau des muscles extenseurs du genou impliqués dans des exercices mono-articulaires fatigants, effectués dans un mode de contraction concentrique ou excentrique. Une troisième étude a montré que pour un exercice de marche/ course réalisé à même fréquence cardiaque en montée, à plat ou en descente, la modalité en descente induisait une fatigue musculaire des extenseurs du genou plus importante, avec des altérations contractiles plus marquée. La quatrième étude a montré que seule la modalité en descente induisait une augmentation de l’excitabilité corticospinale, et une réduction de l’inhibition corticale des muscles extenseurs du genou. Les travaux de cette thèse proposent que le mode de contraction musculaire lors d’un exercice n’est, en lui-même, pas un facteur prépondérant des changements neuroplastiques observés pour des muscles impliqués dans l’exercice. Ces changements neuroplastiques seraient au contraire dépendant de la magnitude de la fatigue neuromusculaire induite, elle-même dépendante du mode de contraction musculaireAlong with cardiovascular and neuromuscular changes, mono-articular and locomotor exercises may induced neuroplastic changes from muscles involved, or non-involved, in the exercise. If the effect of exercise intensity or duration on neuroplastic changes has been previously investigated, the effect of the mode of muscle contraction remains unclear. The aim of this thesis was to investigate the effects of the mode of muscle contraction on neuroplastic changes induced a locomotor or a single-joint exercise. The first study showed that the increase in the corticospinal excitability of a non-exercised hand muscle, observed after a walking/ running exercise, was not modulated by the knee extensors mode of muscle contraction. However, a specific modulation of the intracortical networks by the mode of muscle contraction was evidenced using a paired-associative stimulation protocol. Similar findings were made in a second study that investigated corticospinal changes in the knee extensors following a fatiguing single-joint exercise, performed in either a concentric or an eccentric mode of muscle contraction. A third study showed that for a walking/ running exercise performed at the same heart rate in either a inline, a level or a decline condition, the latter condition induced a greater magnitude of neuromuscular fatigue of the knee extensors, with greater contractile impairments. The fourth study reported that only a decline exercise induced an increase in the corticospinal excitability, and a reduction of the cortical inhibition of the knee extensors. Altogether, findings from this thesis suggest that the mode of muscle contraction during an exercise is not, per se, a main factor responsible for neuroplastic changes observed in exercised muscles. Rather, these changes may depend upon the magnitude of neuromuscular fatigue induced, which could depend upon the mode of muscle contraction involved during exercise
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Mardock, Michelle Anne. "Muscular Strength Training Modifies Regulation of Bone Remodeling: Inferences From Serum Biomarkers in Young Women." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/34631.
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Biochemical markers of bone turnover allow inference of the events occurring at the bone tissue level and may detect changes in bone cell activity earlier than densitometric technologies. Serum concentrations of receptor activator for nuclear factor kappa-beta ligand (RANKL), osteoprotegerin (OPG), osteocalcin, and N-telopeptide (NTx) were measured in women aged 20 + 1.5 years (mean + SD) who underwent 32 weeks of unilateral isokinetic concentric or eccentric muscular strength training. Changes in serum biomarkers were compared with changes in arm and leg flexor and extensor muscle strength. Dual X-ray absorptiometry (DXA) measures of bone mineral density (BMD) and bone mineral content (BMC) of the total forearm, total tibia, and total body also were assessed. The mean serum OPG concentration increased from 4.6 + 1.9 pmol/L to 5.2 + 2.1 pmol/L (â 14.9 %, mean + SD; p = 0.05, n = 20) following long-term isokinetic exercise training that also increased elbow extensor and knee flexor muscular strength (p < 0.05) and total forearm BMD (p = 0.04). The ratio of OPG/RANKL also increased over the course of the study (p = 0.045). Serum concentrations of other measured bone biomarkers did not change during training. Serum concentrations of OPG, a suppressor of osteoclastogenesis, increased with high-load muscular strength training that led to local increases in muscle strength and BMD. These adaptations may represent an exercise-mediated suppression of osteoclast differentiation and activity. The central role of the RANKL-OPG cytokine system in the regulation of bone cell biology is well established. Further research is needed to confirm the efficacy of using serum OPG and RANKL as biomarkers of bone cell metabolism in healthy populations undergoing long-term exercise interventions.Master of Science
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Harvey, Travis Willoughby Darryn Scott. "Effects of concentric and eccentric muscle contractions on IL-6 signaling in human skeletal muscle and downstream regulation of HSP-72 gene expression Is IL-6 signaling involved in exercise-induced cytoprotection? /." Waco, Tex. : Baylor University, 2008. http://hdl.handle.net/2104/5284.
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Ahmadi, Sirous. "Monitoring muscle oxygenation and myoelectric activity after damage-inducing exercise." University of Sydney, 2007. http://hdl.handle.net/2123/2240.
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Doctor of PhilosophyIn this thesis, three experiments were conducted to monitor: (i) muscle oxygenation and electromyographic activity of the biceps brachii after exercise-induced muscle damage (ii) muscle oxygenation after downhill walking-induced muscle damage, and, (iii) muscle oxygenation following a bout of vigorous concentric exercise. Maximal eccentric exercise (EE) of biceps brachii resulted in significantly increased mean resting oxygen saturation and decreased deoxyhaemoglobin. During isometric contractions at 50% and 80% of subjects’ maximum voluntary torque (MVT), oxygen desaturation and resaturation kinetics and volume were significantly decreased after EE, and these declines were significantly prevalent over the following 6 days. Additionally, a significant shift in median frequency intercept (measured by electromyography; EMG) towards lower frequencies was observed during isometric contractions at both 50% and 80% MVT after EE in the exercised arm. After an exhaustive session of downhill walking, another form of EE, resting total haemoglobin and oxyhaemoglobin decreased. Furthermore, during isometric contractions at 30%, 50% and 80% of MVT, prolonged and significant increases were observed in oxygen desaturation and resaturation kinetics and volumes after ambulatory EE. In contrast to the two EE experiments, concentric contractions did not evoke any prolonged changes in muscle oxygenation. Collectively, the findings of this thesis revealed significant and prolonged changes in muscle oxygenation at rest and during exercise, following sessions of strenuous eccentric exercise. Although not clear, the possible mechanism responsible for the changes in muscle oxygenation after EE could be increased resting muscle oxygen utilization due to probable muscle damage and a subsequent requirement of energy demanding repair processes. Concentric exercise resulted in fatigue, but it did not affect muscle oxygenation. Although a prolonged reduction in EMG median frequency intercept was observed after EE, this was not closely time-associated with the biochemical, anthropometric or functional markers of muscle damage.
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Hoessly, Margaret. "The effect of concentric and eccentric muscle action on muscle stiffness at the knee in subjects with spasticity of the quadriceps dissertation submission to Auckland University of Technology for the degree of Master of Health Science, January, 2003." Full thesis. Abstract, 2003. http://puka2.aut.ac.nz/ait/theses/HoesslyM.pdf.
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Rosa, Arianna. "Revisione della letteratura sull’efficacia dell’esercizio terapeutico nel trattamento della tendinopatia della cuffia dei rotatori." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21892/.
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La tendinopatia della cuffia dei rotatori rappresenta una delle cause più comuni di dolore e impotenza funzionale della spalla. E' uno dei motivi principali di assenza dal lavoro e assume un alto costo socio economico. Ha un’eziologia multifattoriale, tra cui il sovraccarico causato da movimenti ripetuti e il meccanismo di compressione dato dalla riduzione dello spazio sotto acromiale. È più frequente tra la popolazione di età superiore ai 50 anni. Altro fattore che concorre ad aumentare il rischio della sua insorgenza è la presenza di patologie sistemiche, quali il diabete o i disturbi cardiovascolari.
L'obiettivo di questa revisione sistematica della letteratura è quello di verificare l'efficacia di un approccio basato sull’esercizio terapeutico per il trattamento della tendinopatia della cuffia dei rotatori. Utilizzando le parole chiave appositamente selezionate ho consultato le seguenti banche dati: PubMed, PEDro, Cochrane Library, Cinahl. Ho consultato la bibliografia delle revisioni inerenti all’argomento trattato ed ho selezionato gli articoli più pertinenti.
Risultati: sono stati inclusi nella revisione, 4 studi in forma RCT; i quali hanno messo a confronto varie tipologie di esercizio terapeutico, a resistenza progressiva, contro gravità attraverso l’utilizzo di bande elastiche e manubri. Le tipologie di esercizio e di esecuzione utilizzate all’interno degli studi sono state eterogenee. Ciò che accomuna tutti gli studi è stato l’outcome di valutazione della funzionalità di spalla. Tutte le tipologie di esercizio si sono rivelate efficaci nel trattamento della tendinopatia della cuffia dei rotatori, in termini di recupero della funzionalità e diminuzione del dolore a breve termine. La tipologia di esercizio non si è dimostrata fondamentale, quanto il fatto che il trattamento venisse svolto con un incremento progressivo della resistenza, per rendere possibile l’adattamento delle strutture tendinee e perciò innescare il loro processo di rinnovamento.
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Muramatsu, Lucio Vitorelli 1985. "O ciclo alongamento encurtamento realizado em alta velocidade aumenta a atividade neuromuscular durante as ações excêntricas." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/274680.
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Orientador: Luiz Eduardo Barreto MartinsDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Educação Física
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Resumo: O objetivo do presente estudo foi investigar alterações neuromusculares e biomecânicas induzidas por diferentes velocidades de execução durante o ciclo de alongamento-encurtamento (CAE) realizado de forma contínua. Doze homens (25,0 ± 3,0 anos, 1,80 ± 0,05 m, 79,6 ± 8,8 kg e 8,0 ± 3,2% de gordura corporal) e três mulheres (29,0 ± 3,0 anos, 1,60 ± 0,06 m, 61,6 ± 2,1 kg e 17,1 ± 2,5% da gordura corporal) participaram do estudo. Os voluntários realizaram 3 protocolos com distintas velocidades de execução. O controle das velocidades foi realizado pelo tempo destinado à execução de cada CAE (Lento = 4 s, Médio = 2 s e Rápido = 1 s por ciclo). Cada protocolo consistiu de 20 repetições (CAE) com 10% de 1RM e 5 min de intervalo, realizados no exercício de extensão do joelho. Velocidade angular, aceleração angular, torque e eletromiografia de superfície (EMG) dos músculos vasto lateral, vasto medial e reto femoral foram acessadas. A execução do CAE em altas velocidades requer alta desaceleração no final das ações excêntricas (EXC) e alta aceleração no início das ações concêntricas (CON), aumentando assim o torque e a atividade EMG nesses momentos. Durante o protocolo Rápido, a atividade EMG da EXC foi maior que a CON. A maior produção de torque e atividade EMG no final da EXC potencializa o início da CON, diminuindo a atividade EMG nessa fase do movimento. Portanto, o CAE realizado com altas velocidades de execução (~160°/s) aumenta a eficiência neuromuscular no começo da CON, induzindo maior atividade EMG durante a ação EXC em comparação com a CON
Abstract: The aim of the present study was to investigate the neuromuscular and biomechanical changes induced by different speed-controlled stretch-shortening cycles (SSCs). Twelve men (24.8 ± 2.9 years, 1.80 ± 0.05 m, 79.6 ± 8.8 kg, and 8.0 ± 3.2% of body fat) and three women (29.0 ± 3.6 years, 1.60 ± 0.06 m, 61.6 ± 2.1 kg and 17.1 ± 2.5% of body fat) participated in the study. The three different speed-controlled SSCs (Slow = 4 s, Medium = 2 s and Fast = 1 s per cycle), were performed on the knee extension machine, consisting of 20 repetitions (SSCs) with 10% of 1RM and 5 min rest. Angular velocity and acceleration, torque and Surface EMG of the vastus lateralis, vastus medialis, and rectus femoris muscles were recorded. During the Fast, EMGRMS of the eccentric (ECC) phase was higher than in the concentric (CON). The acceleration, torque and EMG activity increased in the later phase of the ECC and in the early phase of the CON. Higher torque production and EMG activity in the later part of ECC potentiates the early phase of CON, decreasing EMG activity of these action. Therefore, fast SSCs (160°/s) increases neuromuscular efficiency of CON and induces higher EMG activity in ECC compared to CON
Mestrado
Biodinamica do Movimento e Esporte
Mestre em Educação Física
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Ferreira, Jean de Paula. "Redução do torque concêntrico e isométrico de joelho e tornozelo em indivíduos diabéticos não é dependente da presença de polineuropatia." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8277.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Contextualization: The Diabetes Mellitus (DM) is an epidemic disease in the world and stay associated with right index of morbidity and mortality and about 90% of cases of DM are type 2 (DM2). DM2 develop by inflammatory mechanisms carrying the insulin resistance and consecutively blond hyperglycemia. Believes that in chronic stages the diabetes causes musculoskeletal dysfunctions can be related to inflammatory and metabolic alterations of the DM2 or with diabetic polyneuropathy. Some studies identified the musculoskeletal alteration in diabetic subjects. However not is clearly if the polyneuropathy cause muscle alteration proportionality sensitive alterations. Also weren’t observed studies that analyzed the torque in subjects with DM2, considering others factors that could influence the muscle torque production and also not were observed studies analyzing the torque in diabetic subjects during different types of contractions (concentric, eccentric and isometric). Objectives: The aim of the present study were analyze the torque at concentric eccentric and isometric muscle contractions in diabetic subject with and without polyneuropathy comparing with a control groups. Methods: The peak torques of flexion and extension were acquired using an isokinetic dynamometer, in sitting position. During concentric and eccentric contractions, the joint speed was set at 60°/s. Five maximal voluntary contractions were acquired for concentric and eccentric and 2 for isometric, with a rest interval of 1.5 minutes. The sequence of the tests was randomized and verbal and visual feedback were standardized and delivered to all subjects by the same person. Three groups of adult males were selected for this study (1) Control group (healthy non-diabetic patients, n=33), (2) Diabetic group (patients with diabetes mellitus without polyneuropathy, n=31), (3) Neuropathic group (patients with diabetic polyneuropathy, n=28). The Neuropathic group was defined according to a fuzzy model of signs and symptoms. Differences between groups were calculated with one way ANOVA for parametric knee variables (α of 5%) and Mann Whitney and Willcoxon for non-parametric ankle variables (adjusted α of 1.6%). To describe effect sizes, Hedges’ g was calculated. Results: Irrespective of polyneuropathy, both diabetic groups presented lower peak torques of knee and ankle, both for isometric contraction and for concentric flexion and extension. Other factors beside the polyneuropathy and early in the diabetes onset, may be influencing in the muscle strength production. The eccentric contraction was not different between any groups.
Contextualização: A Diabetes Mellitus (DM) se tornou uma doença epidêmica em todo mundo, e também está associada a altos índices de morbidade e mortalidade. Cerca de 90% dos casos são de DM do tipo 2, que desenvolve por meio de mecanismos inflamatórios que levam à resistência à insulina e consecutivamente à hiperglicemia sanguínea. Acredita-se que em estágios avançados a DM2 cause disfunções musculoesqueléticas, que podem estar relacionadas às alterações inflamatórias e metabólicas dessa doença ou à polineuropatia diabética (PND). Alguns estudos já identificaram alterações musculoesqueléticas em diabéticos. No entanto, ainda não está claro, se a polineuropatia acomete o sistema musculoesquelético, na mesma proporção que o sistema sensorial é acometido. Também não se observa na literatura, estudos que tenham analisado o torque de DM2, considerando outros fatores que podem influenciar a produção de torque e estudos que tenham analisado o torque nos três tipos de contrações (concêntrica, excêntrica e isométrica). Objetivo: O objetivo do presente estudo foi analisar o torque nas contrações concêntrica, excêntrica e isométrica em indivíduos com DM2, com e sem polineuropatia, comparados a um grupo controle sem DM. Métodos: Foram analisados três grupos de homens adultos (total 92), similares na distribuição de sexo, idade e características antropométricas: Controles não diabéticos (n=33); DM2 (n=31); PND (n=28). A PND foi avaliada por meio de um modelo Fuzzy. O pico de torque nas contrações concêntrica, excêntrica e isométrica foi avaliado com um dinamômetro isocinético de cadeira durante a flexão e extensão do joelho e dorsiflexão e flexão plantar do tornozelo. As diferenças entre os grupos foram calculadas com ANOVA one way, para as variáveis paramétricas de joelho (α of 5%) e Mann Whitney e Willcoxon para dados não paramétricos das variáveis do tornozelo (α ajustado de 1.6%). O tamanho de efeito foi calculado usando Hedges’ g. Resultados: Independente da polineuropatia, ambos os grupos diabéticos apresentaram menor torque concêntrico e isométrico de joelho e tornozelo, comparados aos Controles, mas sem diferença entre si. Para o torque excêntrico não houve diferença entre os três grupos em todos os movimentos e articulações avaliadas. Conclusão: A diminuição do torque concêntrico e isométrico em DM2 ocorre mesmo antes da instalação da PND, em tornozelo e joelho, enquanto o torque excêntrico permanece preservado nesses movimentos em diabéticos, independentemente da PND. Observa-se acometimento proximal e distal, com tamanhos de efeito maiores para os movimentos do joelho.
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Spiteri, Tania. "Neuromuscular and biomechanical characteristics of change of direction and agility performance." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2015. https://ro.ecu.edu.au/theses/1662.
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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
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Potts, Geoffrey. "Biomechanic analysis of 'heavy-load eccentric calf muscle' exercise used in the rehabilitation of achilles tendinosis a dissertation submitted in partial fulfilment for the degree of Master of Health Science, Auckland University of Technology, January 2005." Full thesis. Abstract, 2005. http://puka2.aut.ac.nz/ait/theses/PottsG.pdf.
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Johnson, Shelley. "Biomechanical analysis of a 'heavy-load eccentric calf muscle' rehabilitation exercise in persons with Achilles tendinosis a dissertation submitted to Auckland University of Technology in partial fulfilment of the requirements for the degree of Master of Health Science (MHSc), 2008 /." Click here to access this resource online Click here to access this resource online, 2008. http://aut.researchgateway.ac.nz/handle/10292/536.
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