Dissertations / Theses on the topic 'Fatigue – Physiological aspects'

Exercise induced fatigue can have a negative impact on motor skill performance. While part of the decline is attributable to physiological factors that directly influence the coordination of movement, psychological factors may also contribute. Typically, motor learning environments encourage the accumulation of task-relevant declarative knowledge, which can be depended on to consciously support performance. The literature suggests that skills learnt in this way are vulnerable to demanding performance environments, including those in which the performer is fatigued. Recent empirical work has demonstrated that ‘implicit’ motor learning environments, devised to limit declarative knowledge buildup and/or dependence on working memory, promote resilient skill performance even after exhaustive fatigue protocols. Such findings imply that dependence on declarative knowledge to support motor skill execution may be a limiting factor under physiologically fatigue. However, it remains unclear the effect fatigue has on attentional resources, such as working memory. Using established experimental paradigms and EEG methodology, a research project was designed to investigate. Two explanations were considered: (1) fatigue distracts attention away from the control of movement or (2) fatigue directs attention to the skill, which interferes with automated control of the movement. In this study novice participants were allowed to freely accumulate declarative knowledge before completing a targeted muscle-fatigue protocol. A probe response paradigm assessed participants’ ability to recall the position of movement at the time a tone sounded, under the assumption that better recall reflects skill-focused attention. Neural activity was monitored by wireless EEG technology. Neural co-activation (or coherence) between brain regions associated with motor planning (Fz or F3) and with verbal-analytical processing (T3) has been suggested to reflect conscious control of motor skills. Therefore, a fatigue induced increase in T3-F3 coherence can be interpreted as increased conscious involvement in movement control, whereas, a decrease suggests a shift of attention away from movement control. The data collected suggests that to some extent fatigue raises visual-spatial and verbal-analytical contributions to motor control, but highlights methodological issues and limitations of the work.
published_or_final_version
Human Performance
Master
Master of Philosophy

The purpose of the study was to investigate the effects of fatigue on the lower extremity landing strategies of males and females. Twelve recreationally active males (n = 6) and females (n = 6) (nine used for analysis) performed repetitive drop jumps until they could no longer reach 20% of their initial drop jump height. Kinematic and kinetic variables were assessed during the impact phase of all jumps. At initial ground contact, males exhibited greater extension at the hip and knee and less plantar flexion than females. However, females performed more eccentric work during the impact phase of landing. Fatigue resulted in an increased extension at the hip, knee, and ankle for both genders, but did not have an effect on the peak VGRF. Fatigue also resulted in an increase in work performed at the ankle and an approximately equal reduction in work performed at the knee for both genders. Investigation of the peak powers revealed that as a result of fatigue, females utilized a landing strategy in which more energy was absorbed at the knee during the early part of the impact phase. The increased reliance on the knee musculature to dissipate kinetic energy during the impact phase of landing demonstrated by females may be a reason for the commonly seen gender disparities in injury rates. Furthermore, the shift towards energy absorption during the initial part of the impact phase when noncontact injuries are known to occur, exhibited by females, may indicate a greater injury risk for females.
School of Physical Education, Sport, and Exercise Science

Road traffic accidents are a serious burden to the health systems of many countries especially in South Africa. Research aimed at reducing traffic related accidents is of importance as traffic crashes are rated as the second leading cause of fatalities in South Africa and ninth in the world. Despite the extensive efforts into research and development of new technology, driver fatigue still remains a cause of vehicle accidents worldwide. Fatigue plays a role in up to 20% of vehicle accidents with many being serious or fatal. Numerous coping behaviours are employed by drivers to counteract the negative effects of fatigue. The most common coping behaviours include taking short naps, talking to passengers, listening to the radio, opening windows and drinking stimulants. Driving breaks have long been identified as an effective countermeasure against fatigue. Most research done in driving breaks has investigated the duration of the breaks, activity undertaken during the break and the frequency of the breaks taken outside the vehicle. However limited literature is available on the effectiveness of breaks in counteracting the effects of fatigue. The objective of the current study was aimed at assessing whether short duration breaks are an effective countermeasure against fatigue. Physiological, neurophysiological, subjective and performance measures were used as indicators for fatigue. Additional focus of the research was determining whether breaks were more or less effective at counteracting the effects of fatigue at different times of day. Twelve participants were recruited for the study, six males and six females. The participants were required to perform a driving task on a simulator for 90 minutes. The study consisted of four independent conditions, namely driving during the day with breaks, driving during the day without breaks, driving during the night with breaks and driving during the night without breaks. The without breaks conditions were similar except that they occurred at different times of the day, one session at night and the other session during day time, as was the case for the conditions with breaks. The driving task used in the current study was a low fidelity simulator tracking task. The participants were required to follow a centre line displayed on a tracking path as accurately as possible. The measurements that were recorded in this study included physiological, performance, subjective and neurophysiological. Physiological measures included heart rate and heart rate variability (frequency domain) and core body temperature. The ascending threshold of the critical flicker fusion frequency was the only neurophysiological measurement included in the current investigation. Performance was quantified by mean deviation from a centre line participants were meant to track. Two rating scales were used: Karolinska sleepiness scale and the Wits sleepiness scale were used for the measurement of subjective sleepiness. Heart rate, heart rate variability and mean deviation were measured continuously throughout the 90 minute driving task. Critical flicker fusion frequency, temperature and the subjective scales were measured before and after the 90 minute driving task. The results indicated that the short duration breaks during day time had a positive effect on driving performance; however the breaks at night had a negative effect on driving performance. Heart rate was higher during the day compared to night time and the heart rate variability high frequency spectrum values were lower during the day condition, to show the activation of the sympathetic nervous system which is characteristic of day time. The night conditions had lower heart rate values and higher heart rate variability high frequency values, which show the activation of the parasympathetic nervous system which is dominant during periods of fatigue and night time. Subjective sleepiness levels were also higher at night compared to day time.

This study examined the effects of 14 days of L-carnitine supplementation on blood and muscle lactate concentrations, and carnitine fractions, during high intensity sprint cycling exercise. Eight subjects performed three experimental trials - control I (CON I, 0 days), control II (CON II, 14 days), and L-carnitine (LCN, 28 days). Each trial consisted of a 4 min ride at 90% VO2max, followed by a rest period of 20 min, and then 5 x 1 min rides at 115% VO2max (2 min restbetween each). Following CON II, all subjects began dietary supplementation of L-carnitine for a period of 14 days (4 g/day). L-carnitine supplementation had no significant effect on either muscle carnitine or lactate concentrations following the 4 min 90% ride. Plasma total acid soluable and free carnitine concentrations were significantly higher at all time points following supplementation. Differences observed in blood hydrogen ion and lactate concentrations between CON I and CON II appear to be the result of an order effect. The data from the present investigation indicate that L-carnitine supplementation has no significant effect on blood or muscle lactate accumulation following high intensity sprint cycling exercise.
School of Physical Education

The purpose of this study was to examine VT and LT in boys and men. Eight boys (10-11 years) and nine men (18-30 years) completed a graded exercise test on a cycle ergometer. A two-way (group x threshold) ANOVA compared physiological responses (V02 1/min and ml/kg/min, percentage of V02max, and HR) at VT and LT. Statistical significance was set at P < 0.05. No significant interaction was observed. Significant main effects for group included a higher V02 (1/min) in the men, and a higher percentage of VO2max in the boys. Significant main effects for threshold showed all variables were greater at VT than LT. Within each group, all variables were significantly higher at VT than LT. For the boys and all subjects together, significant correlations between thresholds were observed for V02 (1/min and ml/kg/min) and HR, but not percentage of VO2max. For the men alone, no significant correlations were found. Together, these results suggest that physiological changes associated with LT may contribute to the onset of VT, and the occurrence of the thresholds (expressed as a percentage of VO2max) declines with maturation.
School of Physical Education

The purpose of this study was to investigate the effects of fatigue on the accuracy and selected biomechanic variables of jump shot performance. Five subjects were filmed with two high speed cine cameras during pre-fatigue and post-fatigue conditions. The accuracy data were acquired by recording the results of thirty pre-fatigue and thirty post-fatigue, fifteen foot jump shots. The biomechanical data were gathered from film records of every third trial in the pre-fatigue and post-fatigue shooting. Biomechanical analysis variables were acquired using a ten point body model. With these data the following biomechanical variables were analyzed in the pre-fatigue and post-fatigue condition: (1) height of release (2) angle of release (3) absolute shoulder flexion angle at release, and (4) angle of shoulder abduction. Results of the study showed that there is no decrease in accuracy of jump shot performance after fatigue. Fatigue slightly effects the height of release in jump shot performance. Fatigue does not decrease the angle of release in jump shot performance. Fatigue does cause a decrease in the shoulder angle in jump shot performance. There is no decrease in shoulder abduction after fatigue . The study also showed that there are apparently many biomechanical techniques in high percentage shooters, and the presence of fatigue affects selected jump shot biomechanics differently in each shooter.

Individuals are required to manage multiple tasks which require strategic allocation of time and effort to ensure goals are reached efficiently. By providing the worker with autonomy over their work, performance and worker well-being have improved. This increased control allows individuals to organize work according to the needs of the body, which prevents fatigue leading to improved productivity. When given the option, humans tend to switch between tasks frequently. This behaviour can be used to determine the change in self-regulation strategies. An understanding of human task-switching behaviour is important for the design of job rotation systems. However, there is a lack of evidence explaining the factors motivating the need to switch between tasks. This study aims to use physiological, subjective and behavioural measures to explain the factors influencing selfregulation through the act of task-switching. Three primary hypotheses were developed to explain the factors underlying taskswitching behaviour. It was hypothesized that the degree of boredom experienced, the effort required to perform the task and the resource usage induced by the task are factors responsible in deciding task switching behaviour. Participants (17 males and 17 females) switched freely between five different information-processing tasks for the 45 minutes. Participants were allowed to switch back and forth between tasks and did not have to conduct all five tasks. The following measures were recorded during the experiment: subjective measures of boredom, mental effort, task frustration and perceived performance of the tasks; energy consumption and physiological measures of effort (HR, HRV and body temperature) and behavioural measures, including duration and frequency of task. Perceived boredom was found to differ among the tasks and before and after the experiment. The average boredom rating at each task transition for all tasks exceeded a score of 2.5 out of a possible 4. There were no significant changes in physiological measures between the beginning and end of the task trials. However, changes in physiological measures showed a decrease in effort investment following task transition. Heart rate variability was lower for externally-paced tasks than for self-paced tasks, despite the differences in cognitive demands. The most frequent task-switch combination occurred between tasks of high and low cognitive demand. The least frequent task-switching combination occurred between tasks of similar characteristics, which produced no differences in physiological responses. Task-switching behaviour was influenced by the degree of boredom, and therefore more time was spent on less monotonous tasks. The level of physiological effort required for the task affected task-switching behaviour. Task switches were made before any changes in effort took place in an attempt to maintain task efficiency. It appears plausible that a task switch was made to reduce effort investment and activation levels. The type of information processing resources used by different tasks affected the task-switching combinations. Individuals tended to switch between tasks of differing resources so that those in limited supply were able to replenish. Therefore the findings from this study can potentially be used to improve the design of job rotation systems. Such improvements may enhance productivity and worker well-being by inhibiting the onset of down regulation and fatigue processes. This study showed that autonomy is necessary for individuals to regulate behaviour to suit human needs.
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Fatigue is a state that, although researched for many years, is still not completely understood. Alongside this lack of a general understanding of fatigue is a lack of knowledge on the processes involved in the regulation of fatigue. The existing theories relating to regulation are focussed on mental effort regulation, suggesting that performance outcomes are co-ordinated by effort regulation that functions by making alterations to physiological processes and strategic adjustments at a cognitive level in response to cognitive demands and goals. Since fatigue is a multi-dimensional construct with psychological, physiological, and behavioural effects that respond to endogenous and exogenous variables, it follows then that fatigue assessment techniques ought to include multi-dimensional measures to acquire a holistic depiction of the fatigue symptom. This study aimed to assess whether or not a mechanism that regulated fatigue during sustained task execution could be identified and whether this mechanism resulted in regulation patterns that were distinct to a specific task. An additional aim of the study was on assessing whether the manner in which performance, psychophysical and subjective variables were modified over time followed a similar regulation pattern. The research design was aimed at inducing task-related fatigue twice on two different occasions in the same participants and evaluating the resultant changes in fatigue manifestation. This was done to assess the ability of participants to cope with fatigue as a result of previous experience. The research protocol included three tasks executed for an hour aimed at targeting and taxing the sensory, cognitive, motor resources, each task performed twice. 60 participants were recruited to participate in the current study, with 20 participants – 10 males and 10 females – randomly assigned to each of the three tasks. The cognitive resource task consisted of a memory recall task relying on working memory intended to evaluate the extent of reductions in memory and attention. The sensory resource task consisted of a reading task measuring visual scanning and perception designed to evaluate the extent of reduced vigilance. The motor resource task consisted of a modified Fitts’ stimulus response task targeted at monitoring the extent of movement timing disruption. Performance measures comprised of: response delay and the number of correctly identified digits during the cognitive resource task, the amount of correctly identified errors and reading speed during the sensory resource task, response time during the motor resource task, and responses to simple auditory reaction time tests (RTT) initiated at intervals during the task and then again at the end of each task. Physiological measures included ear temperature, eye blink frequency and duration, heart rate (HR), and heart rate variability (HRV). Subjective measures included the use of the Ratings of Perceived Exertion Category Ratio 10 scale (RPE CR 10) to measure cognitive exertion and the NASA-Task Load Index (NASA-TLX) to index mental workload. Eye blink frequency and duration, HR and HRV were sensitive to the type of task executed, showing differing response patterns both over the different tasks and over the two test sessions. The subjective measures indicated increasing RPE ratings over time in all tasks while the NASA-TLX indicated that each task elicited different workloads. Differing task performance responses were measured between the 1st test session and the 2nd test session during all tasks; while performance was found to improve during the 2nd test session for the motor and sensory tasks, it declined during the cognitive task. The findings of this research indicate that there was a regulatory mechanism for fatigue that altered the manner in which performance, psychophysical and subjective variables were modified over time, initiating a unique fatigue regulation pattern for each variable and each task. This regulation mechanism is understood to be a proactive and protective mechanism that functions through reducing a person’s ability to be vigilant, attentive, to exercise discernment, and to direct their level of responsiveness, essentially impacting how the body adapts to and copes with fatigue. The noted overall findings have industry implications; industries should consider accounting for the effects of this regulatory mechanism in their fatigue management interventions, specifically when designing job rotation and work/rest schedules because each cognitive task, having elicited a unique fatigue regulation pattern, ought to also have a different management program.
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Driver fatigue is a complex phenomenon that has a range of causal factors including sleeprelated and task-related factors. These manifest as different safety and performance outcomes. Extensive research has been applied to linking these factors to performance impairment. However, little research focuses on the mechanisms by which this link exists. This research project therefore focuses on the processes underlying how driving performance is controlled and maintained during the development on non-sleep-related driver fatigue. The main aim was to establish whether progressive impairment of driving control over a prolonged drive could be attributed to a depletion of attentional resources, as proposed by Resource Theory, or to a withdrawal of effort, as proposed by Effort-Regulation Theory. As a multicomponent skill, driving requires perception, cognition and motor output. The secondary aim of this research was therefore to assess whether a prolonged drive impairs stage-specific information processing. Participants (n=24) in three experimental groups performed a 90-minute simulated drive wherein they were expected to keep the bonnet of a car on a lane (tracking task). The three groups differed in terms of lane width: small, medium and large, corresponding to low, medium, and high task-demand, respectively. To assess the impacts of this task on stagespecific information processing, participants performed a set of resource specific tests before and after the prolonged drive. Each task had two difficulty variations to ensure that performance decrement was due not only to the task-characteristic, but specifically to resource depletion. The tests probing information processing were: a modified Fitts' tapping task for motor programming, a digit recall task for perception, and an object recognition reading task for cognition. Performance was measured as lateral deviation of the car. Physiological measures included heart rate frequency (HR) and various time- and frequencydomain heart rate variability (HRV) parameters, eye blink frequency and duration. The Borg CR-10 scale was used to evaluate subjective effort and fatigue during the task. Driving control declined over time and was supplemented by HR, HRV, blink frequency and duration, indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Driving control declined to a greater extent in the large road width group and reflected a lower parasympathetic activity, whereas the inverse was observed for the small road width group. Resource tests reveal a non-specific impairment of information processing following the prolonged drive. However, this was accompanied by an increase in parasympathetic activity. Overall, results indicate that Effort-Regulation Theory better accounts for the impairment of driving control in prolonged driving than does Resource Theory. This suggests that the impact of fatigue is guided more by task goals and intrinsic motivation than by the manner in which the fatigue state developed. Moreover, performance impairment by effort-regulation is dependant more on time on task than on task-demand

Worldwide, motor accidents are responsible for a large number of deaths and disabilities (Connor et al., 2001), and one of the major causes of motor accidents is driver fatigue. Although majority of drivers are aware of the dangers of fatigued driving, accidents related to this continues to contribute to a large percentage of all accidents, between 5 and 50% (Nilsson et al., 1997; Williamson et al., 2011). The purpose of the research was to establish the effect that fatigue renders on an individual’s peripheral visual field and to determine whether a decrement in driving performance occurs at the same rate as a decrement in peripheral visual performance. Fatigue was induced through time of day as well as time on task. Sixteen students from Rhodes University were recruited, subject to no previous sleep disorders, among other criteria. Each participant was required to partake in two conditions, namely a day condition (09h00–11h00) and a night condition (23h00– 01h00). Each condition consisted of a 90 minute dual task; the primary task was a tracking task, in which participants were instructed to track a white line as accurately as possible. A secondary peripheral response task was introduced, in which participants were instructed to respond as quickly as possible to the peripheral stimuli, by pressing one of two clickers located on the steering wheel. The peripheral stimuli were located at 20º, 30º and 40º visual angle. Psychophysiological, performance and subjective measures were obtained before, during and after the main task. The pre- and post-tests included core body temperature, critical flicker fusion frequency threshold, a digit span memory test, Wits Sleepiness Scale and a NASA-TLX questionnaire. The psychophysiological and performance measures of heart rate, heart rate variability, blink frequency, blink duration, lane deviation, number of saccades towards peripheral stimuli, response time to peripheral stimuli and the percentage of missed peripheral responses were all recorded throughout the 90 minute main dual task. The results revealed significant differences (p<0.05) for heart rate variability, number of saccades towards peripheral stimuli and the Wits Sleepiness Scale, with regard to time of day. For time on task, significant effects were established for lane deviation, response time to peripheral stimuli, percentage of missed peripheral responses, heart rate, heart rate variability, blink frequency, blink duration, critical flicker fusion frequency threshold, core body temperature and the Wits Sleepiness Scale. Eccentricity was analysed and found to be significant for response time to peripheral stimuli, as well as for the percentage of missed peripheral responses; there was a significant increase in both measures with an increase in the stimuli eccentricity. No significances were established for time of day or between the pre- and post-tests conducted for the digit span memory performance; however, a significant interactional effect between the two was established. When assessing the percentage rate of decrement of driving performance compared to the percentage rate in the decrement of the missed peripheral responses, it was found that the percentage rate of decrement was equal for both measures. Thus from this research it can be seen that, concurrent with a decrement in driving performance, there are adverse effects on an individuals' peripheral vision, which have great implications for the safety of workers in industry and transport, as well as motorists. It was also established that time on task is possibly a more appropriate variable to consider than time of day, when implementing work schedules and rest breaks in industry, transport and fields alike, as more significant findings were seen for time on task compared to time of day.
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This study addresses the effects of the changing workforce and the physiological and psychological benefits of fitness. The purpose of this experiment is to test the relationship between situational stressors, perceived fitness, exercise locus of control, self-control, and perceived stress.

Background: The musculoskeletal demands placed on the lower limb musculature of fast bowlers over time have not received much attention. In particular, measures of muscle recruitment changes have, to the author’s knowledge, not been considered. Objective: The present study, therefore sought to establish any associations between an eight over, simulated fast bowling spell, and muscle activation patterns, power output, perceptual demands, and changes in performance. This will enable improvements in the development of training programmes. Methods: Players’ were required to attend two sessions in total. The purpose of the initial session was to collect specific demographic, anthropometric and physiological data and injury history information from each player. In addition, this first session allowed for habituation with the treadmill, the jump meter and all other equipment involved in experimentation. The second testing session involved electrode attachment sites being identified on player’s dominant leg. The areas were then shaved, wiped with an alcohol swab and left to dry, to ensure good connectivity. Pre- and post- measures of muscle activity and functional strength of the lower limbs were recorded in the Department of Human Kinetics and Ergonomics. The protocol took place at the Kingswood High Performance Centre, which is in close proximity to the initial testing site. The protocol involved players bowling eight overs (48 balls). During the protocol, accuracy, ball release speed and perceptual measures were recorded at the end of each over. After the protocol, players were driven back to the Human Kinetics and Ergonomics Department where post-testing measures were completed. The dependable variables of interest were muscle activation, functional strength of the lower limbs, ‘local’ ratings of perceived exertion (RPE), body discomfort, accuracy, and ball release speed. Results: For all muscles it was shown that, as the speed increased so did the muscle activity in players’ lower limbs. There were no significant changes in muscle activity preversus post-protocol. There was however, a general trend of decreasing muscle activity post protocol at higher testing speeds. There were significant (p<0.05) decreases in peak power following the simulated eight over bowling spell. ‘Local’ RPE displayed a significant (P<0.05) increase with each additional over and were observed to reach the ‘heavy’ category. The players’ highest discomfort area was in the lower back, with 13 players perceiving discomfort in this region following the eight over spell. The shoulder and chest were another two areas player’s indicated discomfort with eight players selecting the dominant shoulder. Seven players complained of the dominant side pectoral muscle, leading foot and dominant latissimus dorsi muscle being uncomfortable. Interestingly, the dominant pectoral showed the highest body discomfort ratings amongst players. There were no significant changes in accuracy between overs although there were large interindividual differences in accuracy points between players. The decrease in ball release speed observed during over seven was shown to be significantly (p<0.05) lower than overs one to four. Conclusion: The power output and perceived strain results of the players, appears to indicate the presence of fatigue in players. However, the results are not conclusive, as the fatigue was not shown in muscle recruitment patterns, as well as the body discomfort ratings. There was a non-significant trend observed in the lower limb muscle activation decreasing at higher speeds. Players were able to maintain accuracy. However, the significantly lower ball release speed observed during over seven showed players performance decreasing.

Thesis (MASpor)--University of Stellenbosch, 2007.
ENGLISH ABSTRACT: The purpose of this study was to gain more information on respiratory muscle function of team sports. This was achieved by determining the relationship between anthropometry and respiratory muscle function and the relationship between respiratory muscle function and exercise performance. The degree of respiratory muscle fatigue after a speed endurance test on land and in water was also determined. A total of 62 subjects were tested. The group consisted of 14 netball players (age: 20.9 ± SD 2.0 years; height: 172.5 ± SD 6.1cm and weight: 66.6 ± SD 7.8 kg); 15 rugby players (age: 21.7 ± SD 2.2 years; height: 183.1 ± SD 7.3cm and weight: 92.5 ± SD 13.2 kg); 12 male swimmers (age: 18.9 ± SD 2.5 years; height: 183.3 ± SD 6.5cm and weight: 77.2 ± SD 8.6 kg); 8 female swimmers (age: 17.8 ± SD 1.6 years; height: 168.3 ± SD 5.4cm and weight: 63.9 ± SD 9.8 kg); 7 male control subjects (age: 21.4 ± SD 1.5 years; height: 179.7 ± SD 5.0cm and weight: 80.8 ± SD 10.8 kg) and 6 female control subjects (age: 21.5 ± SD 1.5 years; height: 166.9 ± SD 6.5cm and weight: 60.2 ± SD 6.7 kg). Testing included anthropometric measurements, lung function (FVC test), and respiratory muscle function (baseline MIP, MEP, MVV). Netball -, rugby players and the control subjects performed a speed endurance test on land and the swimmers performed a speed endurance test in the swimming pool. This test was followed by a second MIP measurement 60 and 120 seconds after the sprint endurance test. Respiratory muscle strength showed no correlations to anthropometry for men and women. For men, height, weight, sitting height, biiacromiale breath and waist girth accounted for 17% of the variance in MIP (P = 0.34). The variance in MEP was accounted for 15.6% by height, weight, sitting height, biacromiale breath and waist girth (P = 0.41). For women, weight, sitting height, arm span, biacromiale breath and chest girth accounted for 28.4% of the variance in MIP (P = 0.17), but MEP was accounted for only 22% by sitting height, arm length, arm span and body mass index as well as chest girth (P = 0.32). Respiratory muscle endurance showed correlations to certain anthropometry variables and had a significant regression equations for MVV in men: -312.51 + (2.83 x Arm span) – (0.38 x Sum of 8 skinfolds) and arm span and sum of eight skinfolds accounted for 47.3% of the variance in MVV. Women’s MVV also had a significant regression (P = 0.002): - 106.7 + (1.5 x Body mass) + (1.0 x Arm span) – (0.2 x Sum of 8skinfolds) and weight, arm span and sum of eight skinfolds accounted for 45% of the variance in MVV. Only MIP and MEP had significant correlations (r = 0.63, P < 0.01 and r = 0.66, P < 0.02 respectively) to the speed endurance test on land. Although significant, MVV and FVC showed no correlations to the speed endurance test. Both MIP and MEP had a correlation to the speed endurance test in the water (r = -0.55, P < 0.02 for both). FVC also had a correlation to the speed endurance test, although it was not significant (r = -0.51, P < 0.44). MVV had a poor correlation to the speed endurance test. Sixty seconds after the speed endurance test the land –based group’s (netball and rugby players grouped together) RM were 14.39% fatigued compared to the 9.04% of the water – based group (swimmers) and 41.02% of the control group. One hundred and twenty seconds after the sprint endurance test the land –based group’s RM were 8.43 fatigued compared to the 3.54% of the water –based group and the 24.64% of the control group. In conclusion, anthropometry plays a moderate role in RM endurance but even a smaller role in RM strength. The relationship between RM functions and the speed endurance test varied between the land – and water –based groups, but certain RM function can play a moderate role in the performance in this speed endurance test. All the groups experienced fatigue after the speed endurance test, but the degree was more in the control group followed by the land –based athletes compared to the water –based athletes. This indicates that stronger RM function can lead to less RM fatigue.
AFRIKAANSE OPSOMMING: Die doel van die studie was om die respiratoriese spier funksies van span sporte te bestudeer en is gedoen deur na die verband tussen respiratoriese spier funksies en antropometrie, die verband tussen respiratoriese spier funksies en oefen prestasie en die mate van respiratoriese spier uitputting na oefening te kyk. ‘n Totaal van 62 subjekte is getoets. Die groep het bestaan uit 14 netbal (ouderdom: 20.9 ± SD 2.0 jaar; lengte: 172.5 ± SD 6.1cm en gewig: 66.6 ± SD 7.8 kg); 15 rugbyspelers (ouderdom: 21.7 ± SD 2.2 jaar; lengte: 183.1 ± SD 7.3cm en gewig: 92.5 ± SD 13.2 kg); 12 mans swemmers (ouderdom: 18.9 ± SD 2.5 jaar; length: 183.3 ± SD 6.5cm and gewig: 77.2 ± SD 8.6 kg); 8 dames swemmers (ouderdom: 17.8 ± SD 1.6 jaar; lengte: 168.3 ± SD 5.4cm and gewig: 63.9 ± SD 9.8 kg); 7 mans kontrole subjekte (ouderdom: 21.4 ± SD 1.5 jaar; lengte: 179.7 ± SD 5.0cm and gewig: 80.8 ± SD 10.8 kg) and 6 dames kontrole subjekte (age: 21.5 ± SD 1.5 years; height: 166.9 ± SD 6.5cm and weight: 60.2 ± SD 6.7 kg). Toetsing het die volgende ingesluit: Antropometriese meetings, long funksies en respiratoriese spier funksies (basislyn maksimale inspirasie drukking (MID), maksimale ekspirasie drukking (MED), maksimale willekeuring ventilasie (MWV)). ‘n Spoed uithouvermoë toets op land is deur die netbal –, rugbyspelers en die kontrole subjekte en ‘n uitgevoer en ‘n spoed uithouvermoë toets in die water is deur die swemmers uitgevoer. Beide hierdie toetse is gevolg deur ‘n tweede en derde maksimale inspirasie drukking 60 en 120 sekondes na die toets. Geen korrelasies is gevind tussen antropometrie en respiratoriese spier sterkte vir beide mans en dames. In die geval van mans, het lengte, gewig, bolyf lengte, bi- akromiale breedte en die omtrek van die middel 17% uitgemaak van die variansie in MIP (P = 0.34). Die variasie van MEP is uitgemaak deur 15.6% van lengte, gewig, bolyf lengte, biakromiale lengte en die omtrek van die middel (P = 0.41). Vir dames het gewig, bolyf length, arm reikwydte, bi –akromiale breedte en bors omtrek ’n 28.4% rol gespeel in die variansie van MIP (P = 0.17), maar die variasie in MEP is voorspel met 22% deur bolyf length, arm length, arm reikwydte, liggaams massa indeks en bors omtrek (P = 0.32). Respiratoriese spier uithouvermoê het ‘n korrelasie getoon met sekere antropometriese veranderlikes en ‘n statisties beduidende vergelyking vir mans MWV: -312.51 + (2.83 x Arm reikwydte) – (0.38 x Som van 8 velvoue) waar arm reikwydte en som van ag velvoue was verantwoordelik vir 47.3% van die variansie in MWV. Die dames se MWV het ook ‘n statisties beduidende vergelyking getoon: MWV = -106.7 + (1.5 x gewig) + (1.0 x Arm reikwydte) – (0.2 x Som van 8 velvoue) waar gewig, arm reikwydte en die som van ag velvoue verantwoordelik was vir 45% van die variansie in MWV. Slegs MID en MED het statisties beduidende korrelasies ( onderskeidelik r = 0.63, P < 0.01 and r = 0.66, P < 0.02 ) getoon met die spoed uithouvermoë toets op land. Geen korrelasie is tussen MWV en die geforseerde vitale kapasiteit toetse gevind al was die verband statistiese beduidend. Beide MID en MED het ’n korrelasie met die spoed uithouvermoë toets in die water getoon (r = -0.55, P < 0.02 vir beide). Die geforseerde vitale kapasiteit toets het ook ’n korrelasie met die spoed uithouvermoë toets, tog was dit nie statisties beduidend nie (r = -0.51, P < 0.44). MWV het geen korrelasie getoon met die spoed uithouvermoë toets op land. Sestig sekondes na die spoed uithouvermoë toets is ’n 14.39 % respiratoriese spier uitputting in die land gebaseerde groep (netbal – en rugby spelers), 9.04% respiratoriese spier uitputting in die water gebaseerde groep (swemmers) en ’n 41.02% respiratoriese spier uitputting in die kontrole groep gevind. Na 120 sekondes was die respiratoriese spiere van die land gebaseerde groep steeds 8.43% uitgeput in vergelyking met die 3.54% van die water gebaseerde groep en die 24.64% van die kontrole groep. Dus speel antropometrie ‘n matige rol in respiratories spier uithouvermoë en selfs ‘n kleiner rol in respiratoriese spier sterkte. Die verband tussen respiratoriese spier funksies en die spoed uithouvermoë toets het gevarieer tussen die land – en die water gebaseerde groepe, maar respiratoriese spier funksies kan ‘n matige rol speel in die voorspelling van die prestasie in die spoed uithouvermoë toets. Die kontrole groep het meer respiratoriese spier uitputting ervaar na die spoed uithouvermoë toets, dus beteken dit dat geoefende en ongeoefend persone respiratoriese spier uitputting sal ervaar.

My experiment concerned the influence of chronobiological (circadian) rhythm on fatigue, effort, and cardiovascular (CV) response. It evaluated responses of morning people (Larks) presented an easy or difficult recognition memory task at a time congruent or incongruent with their rhythm. Based on an extension of a conceptual analysis of fatigue influence, my central prediction was that circadian rhythm would combine interactionally with task difficulty to determine effort and associated CV responses. Specifically, effort and associated CV responses were expected to be (1) positively correspondent to task difficulty in the morning (stronger where difficulty is high), but (2) negatively correspondent to difficulty in the evening (stronger where difficulty is low). Preliminary results showed concerning gender effects on difficulty appraisal of the task, thus we examined women and men's data separately. CV findings for women were broadly, but not completely, consistent with predictions. Analyses revealed no group differences in CV response for Lark men.

[Truncated abstract] A reduction in the force-generating capacity of a muscle is the primary indicator of fatigue and the majority of this force loss is the result of peripheral fatigue. However, there is also evidence that the central nervous system (CNS) does not drive muscles maximally during fatiguing exercise, which has led to the concept of central fatigue. The strongest evidence for this comes from interpolated twitch studies showing that transcranial magnetic stimulation (TMS) during a maximal voluntary contraction can produce an increment in force which becomes greater as fatigue develops. In addition, the silent period (SP) duration increases during a fatiguing exercise, suggesting that there is a buildup of intracortical inhibition that might limit central motor drive. In contrast, motor evoked potential (MEP) amplitude increases during fatigue suggesting an increase in corticomotor excitability during exercise . . . The primary finding was a progressive increase in the fMRI signal during exercise, with a reduction following exercise, and signal changes were observed in all regions. These studies provide evidence that central adaptive processes occur during muscle fatigue and highlight the potential to facilitate these processes with interventional paradigms. The findings indicate the extent of cortical changes during fatigue and suggest that there may also be neurohaemodynamic and/or metabolic components to central adaptive processes. Understanding the central response to muscle fatigue should incorporate mechanisms both of central adaptation and central fatigue.

Résumé en français :

L’objectif de nos investigations a été d’étudier, chez le sujet humain, les mécanismes responsables de l'altération des performances motrices au cours du vieillissement. La première étude était destinée d’une part, à comparer la diminution maximale de force observée dans les différents régimes de contraction et, d’autre part, à contribuer à la compréhension des mécanismes à l’origine de la meilleure préservation de force pour le régime excentrique. Etant donné que jusqu’à présent, seuls des facteurs musculaires avaient été proposés afin d’expliquer les différences existant en fonction du régime de contraction, nous nous sommes plus particulièrement intéressés à une éventuelle participation de facteurs nerveux.

Dans la seconde étude, nous avons testé de manière indirecte (via l’enregistrement d’activités réflexes) l’efficacité des afférences périphériques au cours du vieillissement. En effet, sous le contrôle de la commande centrale, celles-ci contribuent également à réguler le niveau d’excitabilité des motoneurones. Une moindre efficacité de celles-ci pourrait donc être un facteur supplémentaire responsable de l’altération de la fonction motrice.

Nous avons ensuite analysé (études III et IV) les propriétés contractiles et le comportement des unités motrices lors de contractions lentes et très rapides (contractions balistiques). Cela nous a permis de vérifier s’il existait chez les seniors une relation entre la diminution de force, de sa vitesse d’installation, et la stratégie d’activation des unités motrices.

Enfin, dans l’étude V, nous avons analysé la fatigabilité neuromusculaire chez les seniors, comparativement aux sujets jeunes. Plus spécifiquement, nous avons étudié les contractions concentriques et excentriques maximales fatigantes. La fatigue n’a en effet pas encore été étudiée lors de ces deux types de contraction chez les adultes jeunes et âgés. L’objectif de cette dernière étude était surtout d’analyser la part relative des mécanismes nerveux et musculaires à l’origine de la fatigue ainsi que leur décours dans le temps en fonction de l’âge des sujets.

L’approche méthodologique utilisée nous a permis d’analyser les modifications fonctionnelles du muscle et de ses unités motrices avec l’âge. Un intérêt tout particulier a été porté aux ajustements de la commande nerveuse et à la compréhension des mécanismes sous-jacents. L’ensemble de nos résultats expérimentaux documentent de manière originale l’interaction étroite entre les adaptations nerveuses et musculaires au cours du vieillissement. Plus largement, notre travail doctoral contribue à une meilleure connaissance de la remarquable plasticité du système neuromusculaire chez l’homme.

Résumé en anglais :\
Doctorat en Sciences de la motricité
info:eu-repo/semantics/nonPublished

Acute sleep loss may lead to elevated fatigue, decreased energy, and diminished cognitive performance. Traditionally, sleep extension is used to restore mood and cognitive function to baseline levels following insufficient sleep, yet this method may not be feasible or preferred. Acute exercise may serve as an affordable and relatively safe intervention to reduce detriments to daytime functioning following sleep loss. The primary purpose of this study was to examine the effects of moderate-intensity aerobic exercise on neurocognitive function following acute sleep restriction. A secondary aim was to examine the effects of exercise in subjective reports of fatigue, energy, and sleepiness following acute sleep restriction. Fifty-six participants, matched by sex, age, and chronotype, were randomly assigned to either an exercise (EX) or seated control (SC) condition. Following a 4-hour sleep restriction protocol, participants completed the oddball paradigm before and after 20 minutes of exercise or stationary sitting. P3 amplitude and latency, arousal, sleepiness, energy, and fatigue were assessed during the experiment. After controlling for pre-test differences, P3 latency was significantly faster following exercise relative to the control group. No significant P3 amplitude differences were observed between conditions. The EX group displayed significant improvements in arousal, sleepiness, energy, and fatigue compared to the SC group. Findings suggest that 20 minutes of moderate-intensity aerobic exercise following acute sleep restriction may improve cognitive processing speeds, as well as improve arousal, sleepiness, energy, and fatigue.

Fatigue induces changes to running form; therefore movement is not as effective or efficient. Reducing the amount of fatigue or its effects on form would be ideal to improve performance while running. Compressive clothing has unknown effects on musculature, however it claims to reduce fatigue. The aim of this study was to see the changes in running form while running to exhaustion and to see how compression tights can effect these changes. Eleven runners ran at their current five-kilometer race pace on a treadmill to voluntary exhaustion in a repeated measures design wearing compression tights and regular shorts while their kinematics, kinetics, heart rate and rate of perceived exhaustion were recorded. There was not a significant difference in time to exhaustion. Fatigue general effects were significant from beginning to end in knee and ankle angle at initial contact with the knee becoming less extended and the ankle less dorsiflexed. Vertical ground reaction loading rate and impact peak were significantly different from beginning to mid point and beginning to end across conditions. Heart rate and rate of perceived exertion increased significantly with fatigue as well in both conditions. Condition effects were significant in stride length and rate with a decreased stride length with compression tights and an increased stride rate with compression tights. The hip experienced a decreased range of motion in the compression tights compared to running shorts. These results indicate that there are effects of fatigue on performance and differences between conditions. These differences did not affect the overall outcome of run as measured in time to exhaustion.
School of Physical Education, Sport, and Exercise Science

Expectations from industry and the community ensure that we live in a 24-hour society. Increased demand for flexibility, capital utilisation and competition have initiated or extended shiftwork operations in many industry sectors such as mining, transport, defence, healthcare, manufacturing and security. The most common problems reported by shiftworkers are disturbed sleep and sleepiness. From a biological perspective this is not surprising because shiftworkers are often required to work at times when their mind and body are driven toward sleep. Shiftworkers may therefore be required to attempt sleep during the day; a time at which their mind and body are programmed to be awake and active. When sufficient recovery doesn't occur regularly, sleepiness and fatigue can accumulate. Traditionally, shiftwork and the work-related fatigue that it can create have been 'managed' by limiting the length of shifts and total number of hours worked per week, month or year. However, this approach fails to acknowledge key factors such as the time-of-day of work. Thus, the aim of this thesis is to provide the background, components and preliminary validations of a model to assess hours-of-work and fatigue in a scientifically appropriate manner.
thesis (PhD)--University of South Australia, 1999.

Neuromuscular electrical stimulation (NMES) has been shown to be effective for recovery of motor function following injury or pathology, however, NMES can impart rapid fatigue and the specific parameters of stimulation that maximize force output and delay the onset of fatigue remain unclear. Frequency, intensity, and pulse pattern are a few of the parameters that can be manipulated to achieve desired outcomes. Strong evidence supports the use of higher frequencies of stimulation to maximize performance of fatigued or paralyzed muscle. Likewise, several studies advocate the use of varied pulse patterns, rather than constant pulses, to maximize force output as well. Much of the research literature regarding NMES use with a pathological population involves spinal injured individuals. Much less is known about the effect of NMES on motor recovery, especially when delivered through varied pulse patterns, in the post-stroke population. The three studies contained herein addressed these issues. In Study 1, submaximal and supramaximal intensities of two variable frequency stimulation patterns and one constant frequency pattern were applied to the thenar muscles of a young healthy population. Results showed marked differences in force output between the two intensities. Submaximal stimulation enhanced the effect of the variable pulses and a greater force response was produced. In Study 2, the same three patterns were applied to the thenar muscles of a post-stroke group and an age-matched able-bodied group at submaximal intensities. Again, differences in force output were evident between the healthy and pathological group, and the variable pulses may have further depressed already weakened hemiplegic muscle. Study 3 compared the effects of a NMES rehabilitation program using a high (40 Hz) and a low (20 Hz) frequency to determine if task-specific improvements were related to frequency used. Results showed that those in the high frequency condition demonstrated greater improvements in strength, dexterity and force accuracy; those in the low frequency condition showed improvements in motor endurance. The results of this work suggest that the intensity, frequency and stimulation pattern of NMES used have a significant impact on the resultant muscle contraction and functional skills gained following stroke and should be carefully considered when implementing a clinical regimen for motor recovery.

The purpose of this study was to investigate how maximal power output (P[subscript max]), as measured via the inertial load technique, changes throughout a collegiate soccer season in relation to training load completed. Furthermore, this study also aimed to describe the time course of recovery of [maximal power output] following two collegiate soccer matches in one weekend. The current investigation involved two experimental periods. The first took place throughout the 2010 Big XII soccer season. Nineteen Division I female collegiate soccer players (19.9 ± 1.2 yrs, 165.1 ± 6.6 cm, 61.0 ± 6.8 kg) from the same collegiate soccer team completed regular inertial load testing and perceptual fatigue questionnaires throughout this study period. These athletes' training was not altered in any way by the investigators throughout the 2010 season. During the second experimental period, two off-season matches were played in one weekend during the 2011 off-season. Training was prescribed by coaches, with the aim of simulating an in-season training week. [Maximal power output] and perceptual fatigue responses were monitored every day throughout the second study period. All training and matches throughout the study were monitored via the session RPE method. The results demonstrated that STARTERS experience much greater load throughout the season than NON-STARTERS (p<0.05, 2247 ± 176 AU and 1585 ± 174 AU), accounted for by increased load experienced during matches. This increased training load throughout the season lead to a decline in [maximal power output] in STARTERS (to 92.3 ± 6%, p<0.05) whilst [maximal power output] was maintained in NON-STARTERS (p>0.05) for the duration of the season. Furthermore, STARTERS experienced greater muscle soreness throughout the in-season period compared to NON-STARTERS. During the second experimental period [maximal power output] declined (p<0.05, 93.3 ± 7%) two days following matches played on the weekend and remained reduced for three days. Notably, two heavy training days in the middle of the training week appeared to have detrimental effects on both [maximal power output] and perceptual fatigue responses. The main finding of this study is that [maximal power output] declined throughout the middle and latter parts of the season in STARTERS, after experiencing significantly greater training loads than NON-STARTERS throughout the season. The current findings, combined with previous investigations, suggest that the inertial load technique may be useful in monitoring fatigue in team sport athletes.
text

Lo Chi-yan.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (leaves 42-51).
Abstract in English and Chinese; questionnaires in Chinese.
Abstract --- p.i
Acknowledgments --- p.iv
Table of Contents --- p.v
Chapter CHAPTER 1 --- Introduction --- p.1
Why is empirical research on driver sleepiness important? --- p.2
Prevalence of driver sleepiness --- p.2
Driver sleepiness as a risk factor for traffic accidents --- p.3
Why should taxi driver sleepiness be studied? --- p.6
Variations in sleepiness and vigilance and driving performance within a shift and comparison between daytime and nighttime drivers --- p.8
"The impact of circadian typology on sleep, sleepiness, vigilance and driving performance" --- p.11
Bright light exposure --- p.14
Overview of the present study --- p.18
Chapter CHAPTER 2 --- Main study --- p.20
Recruitment and Characteristics of Participants --- p.20
Procedure --- p.20
Instruments --- p.23
Chapter CHAPTER 3 --- Results --- p.28
Chapter CHAPTER 4 --- Discussion --- p.36
References --- p.42
Figures --- p.52
Tables --- p.55
Appendices --- p.62