Health and fitness of young, healthy adult females and the effect of an eight week pilates intervention
- Authors: Eaton, Lara Lee
- Date: 2018
- Subjects: Physical fitness for women -- South Africa -- Makhanda , Pilates method , Exercise for women -- South Africa -- Makhanda , Exercise -- Health aspects -- South Africa -- Makhanda , Exercise -- Physiological aspects -- South Africa -- Makhanda
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58267 , vital:27112
- Description: Purpose: The first phase of this study aimed to investigate the health and fitness status of young adult females in the local community. The second phase of this study investigated the impact of an eight week progressive Pilates intervention on selected health and fitness parameters in this cohort. Methods: Healthy young adult females aged 18-26 years (n=96), from the local community, partook in once-off tests including anthropometric measures (stature, body mass, Body Mass Index and waist circumference) as well as fitness parameters including balance, flexibility, muscular strength and endurance, and lastly lumbo-pelvic stability. Health measures investigated included blood pressure and spirometry. Where possible, results were compared to those of similar populations from national surveys or published normative data. Sedentary volunteers from this cohort were then randomised into a Pilates Exercise (PEx, n=12) or an inactive Control (Con, n=11) group, with their results from Phase 1 serving as baseline measures. Pilates classes were held twice weekly (60 minutes per session). All the measures from phase 1 were repeated at weeks 4 and 8. An additional intervention test included Transversus abdominis recruitment. Participants maintained habitual dietary intake and energy expenditure throughout. Nine PEx group and eight Con group participants completed the intervention. Results: The current sample (phase 1) was found to be healthier than comparative populations from national surveys, and significant differences (p<0.05) were found for all comparisons except Forced Expiratory Volume (FEV1), (p=0.64). Physical activity levels (230 min.week-1) exceeded that of the recommend weekly threshold (150 min.week-1). BMI, waist circumference, blood pressure and spirometry measures were all found to be within suggested healthy normal ranges. Pilates significantly improved lumbo-pelvic stability in the PEx group at weeks 4 (p<0.005) and 8 (p<0.002). Similarly, abdominal (p=0.00, d=1.1), upper limb (p=0.037, d=0.9) and lower limb endurance (p=0.02, d=1.0, between group d=0.73 for PEx) also improved with no changes in the Con group. PEx energy expenditure significantly increased from baseline to weeks 4 (p=0.007, d=10.7) and 8 (p=0.027, d=0.64), however body mass was maintained throughout. Conversely, Minute Ventilation decreased in the PEx cohort (p=0.010, d=0.95) from weeks 4 to 8. The Con group showed significant increases in body mass (p=0.018), leg strength (within-group Cohen’s d=-1.08 between weeks 0-8; d=-2 between weeks 4-8) and dynamic balance (p=0.01, d=-0.5). While no within-group changes were observed, Protein intake was significantly greater (p=0.036, d>0.8 at baseline and week 8) in the PEx group throughout the intervention. Medium between-group effect sizes (d>0.5) were noted for PEx BMI and waist circumference measures at all time points. Further, although not significant, the large within-group effect size (d=-0.84) between baseline and week 8 for PEx systolic blood pressure, suggested the 9 mm Hg was meaningful. The same time period also indicated a large within-group effect size (d=-0.8) for PEx dynamic balance, and a medium Cohen’s d for (d=0.57) PEx static balance. Conclusion: The local population of young adult females was found to be significantly healthier than those of comparable national samples. Further, Pilates participation significantly improved lumbo-pelvic stability and muscular endurance with meaningful changes in systolic blood pressure, and balance in previously sedentary young, adult females. Body mass was also maintained.
- Full Text:
- Date Issued: 2018
- Authors: Eaton, Lara Lee
- Date: 2018
- Subjects: Physical fitness for women -- South Africa -- Makhanda , Pilates method , Exercise for women -- South Africa -- Makhanda , Exercise -- Health aspects -- South Africa -- Makhanda , Exercise -- Physiological aspects -- South Africa -- Makhanda
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58267 , vital:27112
- Description: Purpose: The first phase of this study aimed to investigate the health and fitness status of young adult females in the local community. The second phase of this study investigated the impact of an eight week progressive Pilates intervention on selected health and fitness parameters in this cohort. Methods: Healthy young adult females aged 18-26 years (n=96), from the local community, partook in once-off tests including anthropometric measures (stature, body mass, Body Mass Index and waist circumference) as well as fitness parameters including balance, flexibility, muscular strength and endurance, and lastly lumbo-pelvic stability. Health measures investigated included blood pressure and spirometry. Where possible, results were compared to those of similar populations from national surveys or published normative data. Sedentary volunteers from this cohort were then randomised into a Pilates Exercise (PEx, n=12) or an inactive Control (Con, n=11) group, with their results from Phase 1 serving as baseline measures. Pilates classes were held twice weekly (60 minutes per session). All the measures from phase 1 were repeated at weeks 4 and 8. An additional intervention test included Transversus abdominis recruitment. Participants maintained habitual dietary intake and energy expenditure throughout. Nine PEx group and eight Con group participants completed the intervention. Results: The current sample (phase 1) was found to be healthier than comparative populations from national surveys, and significant differences (p<0.05) were found for all comparisons except Forced Expiratory Volume (FEV1), (p=0.64). Physical activity levels (230 min.week-1) exceeded that of the recommend weekly threshold (150 min.week-1). BMI, waist circumference, blood pressure and spirometry measures were all found to be within suggested healthy normal ranges. Pilates significantly improved lumbo-pelvic stability in the PEx group at weeks 4 (p<0.005) and 8 (p<0.002). Similarly, abdominal (p=0.00, d=1.1), upper limb (p=0.037, d=0.9) and lower limb endurance (p=0.02, d=1.0, between group d=0.73 for PEx) also improved with no changes in the Con group. PEx energy expenditure significantly increased from baseline to weeks 4 (p=0.007, d=10.7) and 8 (p=0.027, d=0.64), however body mass was maintained throughout. Conversely, Minute Ventilation decreased in the PEx cohort (p=0.010, d=0.95) from weeks 4 to 8. The Con group showed significant increases in body mass (p=0.018), leg strength (within-group Cohen’s d=-1.08 between weeks 0-8; d=-2 between weeks 4-8) and dynamic balance (p=0.01, d=-0.5). While no within-group changes were observed, Protein intake was significantly greater (p=0.036, d>0.8 at baseline and week 8) in the PEx group throughout the intervention. Medium between-group effect sizes (d>0.5) were noted for PEx BMI and waist circumference measures at all time points. Further, although not significant, the large within-group effect size (d=-0.84) between baseline and week 8 for PEx systolic blood pressure, suggested the 9 mm Hg was meaningful. The same time period also indicated a large within-group effect size (d=-0.8) for PEx dynamic balance, and a medium Cohen’s d for (d=0.57) PEx static balance. Conclusion: The local population of young adult females was found to be significantly healthier than those of comparable national samples. Further, Pilates participation significantly improved lumbo-pelvic stability and muscular endurance with meaningful changes in systolic blood pressure, and balance in previously sedentary young, adult females. Body mass was also maintained.
- Full Text:
- Date Issued: 2018
Influence of knowledge of the end-point on pacing during a 2000m rowing time trial
- Authors: Ferreira, Dean
- Date: 2018
- Subjects: Rowing -- Training , Rowing -- Coaching , Endurance sports -- Training , Rowers -- Ability testing , Rowing -- Training -- Psychological aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61636 , vital:28044
- Description: Introduction: A typical 2000 m rowing race requires maximal force production over six to eight minutes. Optimal distribution of energetic resources during such a race is vital for optimal performance. There is little research examining the pacing strategies employed by rowers, particularly at the sub-elite level. Aim: The purpose of this investigation was to determine the influence of knowledge of the end-point on pacing during a 2000 m rowing time trial. Methods: Eleven male rowers from a university rowing club volunteered to partake in the study. Each participant completed three experimental trials on an indoor rowing ergometer, each 2000 m. The only difference between the trials was the nature of the information provided beforehand. At the start of the control trial, participants were correctly informed about the distance to be covered. Participants were not informed of the distance to be completed in the unknown trial. For the deceptive trial, participants were told 1000 m would be completed, but when this distance was reached, they were told to continue for another 1000 m. During each trial muscle activity, power output, heart rate, performance time and perceptions of effort were measured.Results: The control trial was significantly (p<0.05) faster than both the unknown and deceptive trials, however the deceptive trial was the fastest of all trials at the 1000 m distance. The unknown trial was slowest at 1000 m and at 2000 m. Muscle activity, RPE, heart rate and power output were significantly (p<0.05) lower in the unknown trial compared to the control and deceptive trial. The control trial exhibited a reverse J-shape pacing profile. The deceptive trial revealed a significant (p<0.05) reduction in performance time, heart rate, power output and muscle activity after the 1000 m interval. The first 500 m interval had the fastest performance and highest power output in all trials. In all trials, RPE was highest at the end of the 2000 m, the greatest reading being obtained at the end of the control trial. During the first 1000 m of the deceptive trial, the dependant variables were similar to those in the control trial. Once the deception was revealed, there was a significant (p<0.05) reduction in the muscle activity, heart rate and power output. Conclusion: The results of this study indicate that accurate end-point information is crucial to the development of an optimal pacing strategy, and ultimately to successful performance. Rowers tend to adopt the reverse J-shape pacing profile most often due to the tactical and physiological benefits offered by this strategy. Unknown or inaccurate end-point information resulted in performance decrements due to the uncertainty associated with the exercise bout.
- Full Text:
- Date Issued: 2018
- Authors: Ferreira, Dean
- Date: 2018
- Subjects: Rowing -- Training , Rowing -- Coaching , Endurance sports -- Training , Rowers -- Ability testing , Rowing -- Training -- Psychological aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61636 , vital:28044
- Description: Introduction: A typical 2000 m rowing race requires maximal force production over six to eight minutes. Optimal distribution of energetic resources during such a race is vital for optimal performance. There is little research examining the pacing strategies employed by rowers, particularly at the sub-elite level. Aim: The purpose of this investigation was to determine the influence of knowledge of the end-point on pacing during a 2000 m rowing time trial. Methods: Eleven male rowers from a university rowing club volunteered to partake in the study. Each participant completed three experimental trials on an indoor rowing ergometer, each 2000 m. The only difference between the trials was the nature of the information provided beforehand. At the start of the control trial, participants were correctly informed about the distance to be covered. Participants were not informed of the distance to be completed in the unknown trial. For the deceptive trial, participants were told 1000 m would be completed, but when this distance was reached, they were told to continue for another 1000 m. During each trial muscle activity, power output, heart rate, performance time and perceptions of effort were measured.Results: The control trial was significantly (p<0.05) faster than both the unknown and deceptive trials, however the deceptive trial was the fastest of all trials at the 1000 m distance. The unknown trial was slowest at 1000 m and at 2000 m. Muscle activity, RPE, heart rate and power output were significantly (p<0.05) lower in the unknown trial compared to the control and deceptive trial. The control trial exhibited a reverse J-shape pacing profile. The deceptive trial revealed a significant (p<0.05) reduction in performance time, heart rate, power output and muscle activity after the 1000 m interval. The first 500 m interval had the fastest performance and highest power output in all trials. In all trials, RPE was highest at the end of the 2000 m, the greatest reading being obtained at the end of the control trial. During the first 1000 m of the deceptive trial, the dependant variables were similar to those in the control trial. Once the deception was revealed, there was a significant (p<0.05) reduction in the muscle activity, heart rate and power output. Conclusion: The results of this study indicate that accurate end-point information is crucial to the development of an optimal pacing strategy, and ultimately to successful performance. Rowers tend to adopt the reverse J-shape pacing profile most often due to the tactical and physiological benefits offered by this strategy. Unknown or inaccurate end-point information resulted in performance decrements due to the uncertainty associated with the exercise bout.
- Full Text:
- Date Issued: 2018
Quantification of pre-competitive sleep/wake behaviour in a sample of South African cyclists
- Authors: Steenekamp, Travis
- Date: 2018
- Subjects: Sleep deprivation , Cyclists Health and hygiene South Africa , Sleep Physiological aspects , Performance , Performance anxiety
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59015 , vital:27408
- Description: The quantification of athlete pre-competitive sleep behaviour is of interest owing to the possibility that sleep loss may have a negative effect on health and performance. The purpose of this study was to monitor and quantify the sleep/wake patterns of South African cyclists prior to competitive races. A total of 336 cyclists, male and female and of differing competition levels, cycling in either the 2015 Tsogo Sun Amashova or the 2016 Telkom 94.7 Cycle Challenge completed an altered version of the Competitive Sports and Sleep Questionnaire. The questionnaire asked cyclists to report on precompetitive sleep over the past year. A subset of 92 cyclists also recorded a Core Consensus Sleep Diary for the three nights leading up to the races. The questionnaire showed that 67% of the cyclists reported worsened sleep at least once prior to competition within the past 12 months. The sleep diary found that the cyclists’ average sleep duration the night before the races was 6h19min (±1h38min), which was significantly less than two and three nights prior to the races. Sleep quality was also shown to deteriorate significantly the night before the races. The contributing factors leading to worsened pre-competitive sleep were the time the cyclists had to wake-up as well as perceived increases in sleep latency and awakenings after sleep onset. Anxiety was found to be the major cause of sleep disturbances. While females were found to be significantly more likely to report having experienced poorer sleep before competition in the past year, the sleep diary showed no difference in sleep the night before the races between the sexes. Females were significantly more likely to report instances of unpleasant dreams and waking up during the night. Again, the sleep diary data did not corroborate these findings. Females were also found to report significantly more accounts of nervousness or thoughts about competition as being the cause of sleep problems. There was no difference in sleep loss the night before competition when comparing competition-level groups. The only significant difference was that recreational cyclists were more likely to report sleeping in foreign environments as a cause of sleep disturbances. Despite a large percentage of cyclists experiencing pre-competitive sleep loss, over half (55%) perceived sleep loss to have no impact on their performance. Analysis of pre-sleep behaviour also revealed that the cyclists engaged in several practices that may have a negative effect on subsequent sleep. The vast majority of the cyclists (61%) indicated having no specific strategy to help them sleep the night before competition. Fifteen percent of cyclists reporting using media devices to help them fall asleep, a practice that has been shown to disrupt sleep. In conclusion, most cyclists, regardless of sex and level of competition experience precompetitive sleep loss attributed largely to anxiety but with the perception that this loss in sleep does not negatively impact their performance.
- Full Text:
- Date Issued: 2018
- Authors: Steenekamp, Travis
- Date: 2018
- Subjects: Sleep deprivation , Cyclists Health and hygiene South Africa , Sleep Physiological aspects , Performance , Performance anxiety
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59015 , vital:27408
- Description: The quantification of athlete pre-competitive sleep behaviour is of interest owing to the possibility that sleep loss may have a negative effect on health and performance. The purpose of this study was to monitor and quantify the sleep/wake patterns of South African cyclists prior to competitive races. A total of 336 cyclists, male and female and of differing competition levels, cycling in either the 2015 Tsogo Sun Amashova or the 2016 Telkom 94.7 Cycle Challenge completed an altered version of the Competitive Sports and Sleep Questionnaire. The questionnaire asked cyclists to report on precompetitive sleep over the past year. A subset of 92 cyclists also recorded a Core Consensus Sleep Diary for the three nights leading up to the races. The questionnaire showed that 67% of the cyclists reported worsened sleep at least once prior to competition within the past 12 months. The sleep diary found that the cyclists’ average sleep duration the night before the races was 6h19min (±1h38min), which was significantly less than two and three nights prior to the races. Sleep quality was also shown to deteriorate significantly the night before the races. The contributing factors leading to worsened pre-competitive sleep were the time the cyclists had to wake-up as well as perceived increases in sleep latency and awakenings after sleep onset. Anxiety was found to be the major cause of sleep disturbances. While females were found to be significantly more likely to report having experienced poorer sleep before competition in the past year, the sleep diary showed no difference in sleep the night before the races between the sexes. Females were significantly more likely to report instances of unpleasant dreams and waking up during the night. Again, the sleep diary data did not corroborate these findings. Females were also found to report significantly more accounts of nervousness or thoughts about competition as being the cause of sleep problems. There was no difference in sleep loss the night before competition when comparing competition-level groups. The only significant difference was that recreational cyclists were more likely to report sleeping in foreign environments as a cause of sleep disturbances. Despite a large percentage of cyclists experiencing pre-competitive sleep loss, over half (55%) perceived sleep loss to have no impact on their performance. Analysis of pre-sleep behaviour also revealed that the cyclists engaged in several practices that may have a negative effect on subsequent sleep. The vast majority of the cyclists (61%) indicated having no specific strategy to help them sleep the night before competition. Fifteen percent of cyclists reporting using media devices to help them fall asleep, a practice that has been shown to disrupt sleep. In conclusion, most cyclists, regardless of sex and level of competition experience precompetitive sleep loss attributed largely to anxiety but with the perception that this loss in sleep does not negatively impact their performance.
- Full Text:
- Date Issued: 2018
Strength and conditioning practices of high school rugby coaches: a South African context
- Authors: Robinson, Bradley Charles
- Date: 2018
- Subjects: Rugby football coaches South Africa , Rugby football Coaching , Rugby football Physiological aspects , Rugby football Training , High school students Social conditions
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63459 , vital:28413
- Description: Although the sport of rugby union is well established, the strength and conditioning practices of high school level players are not well known. Therefore, the purpose of this study was to examine the current strength and conditioning practices that coaches implement at South African high school level rugby. A secondary purpose was to compare practices between different types of schooling systems available in South Africa. An online survey or in person interview (depending on the school), adapted from previous strength and conditioning questionnaires, was conducted with 43 responses; including 28 schools among the top 100 rugby schools in South Africa for 2016 and 15 no-fee paying public schools in the Eastern Cape Province of South Africa. Results indicated that the top 100 rugby schools implement conditioning practices similar to the best-known international practices compared to no-fee paying schools who lacked the knowledge and skills in various strength and conditioning principles. It was found that all no-fee paying school coaches had insufficient qualifications to administer the correct training techniques. Coaches at all schools lacked the appropriate knowledge on injury prevention and scientifically based training programmes. It was concluded that education and skills around the best strength and conditioning practices for school level coaches needs to be improved and particularly in less privileged schools. The main goal being to reduce the risk of injury and improve performance across all sectors of the rugby playing population within the country. This was deemed crucial to the transformation goals set out by the South African Rugby Union, which would benefit from player development in lower socioeconomic schools.
- Full Text:
- Date Issued: 2018
- Authors: Robinson, Bradley Charles
- Date: 2018
- Subjects: Rugby football coaches South Africa , Rugby football Coaching , Rugby football Physiological aspects , Rugby football Training , High school students Social conditions
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63459 , vital:28413
- Description: Although the sport of rugby union is well established, the strength and conditioning practices of high school level players are not well known. Therefore, the purpose of this study was to examine the current strength and conditioning practices that coaches implement at South African high school level rugby. A secondary purpose was to compare practices between different types of schooling systems available in South Africa. An online survey or in person interview (depending on the school), adapted from previous strength and conditioning questionnaires, was conducted with 43 responses; including 28 schools among the top 100 rugby schools in South Africa for 2016 and 15 no-fee paying public schools in the Eastern Cape Province of South Africa. Results indicated that the top 100 rugby schools implement conditioning practices similar to the best-known international practices compared to no-fee paying schools who lacked the knowledge and skills in various strength and conditioning principles. It was found that all no-fee paying school coaches had insufficient qualifications to administer the correct training techniques. Coaches at all schools lacked the appropriate knowledge on injury prevention and scientifically based training programmes. It was concluded that education and skills around the best strength and conditioning practices for school level coaches needs to be improved and particularly in less privileged schools. The main goal being to reduce the risk of injury and improve performance across all sectors of the rugby playing population within the country. This was deemed crucial to the transformation goals set out by the South African Rugby Union, which would benefit from player development in lower socioeconomic schools.
- Full Text:
- Date Issued: 2018
The effects of intermittent task parameters on muscle fatigue development during submaximal dynamic exertions
- Authors: King, Josephine Claire
- Date: 2018
- Subjects: Muscles -- Physiology , Muscles -- Wounds and injuries , Fatigue , Human engineering , Occupational diseases
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63855 , vital:28498
- Description: The negative effects of localised muscle fatigue on accidents, injuries and poor work performance are well known, as is the realisation that modifying task characteristics can minimise fatigue development. A large amount of literature has investigated the effects of task-dependent factors on localised muscle fatigue, most studies have focussed on prolonged or intermittent static (isometric) exertions. Few studies have investigated muscle fatigue development during more complex tasks, namely those which resemble common work activities and which tend to be intermittent and dynamic in nature. More specifically, the interactions between the main intermittent parameters - duty cycle, force level, and cycle time - during dynamic exertions are poorly understood. The purpose of this study was to investigate the effects of cycle time and combinations of duty cycles and force levels on the development of muscle fatigue during submaximal dynamic exertions while the overall mean muscle load was kept constant. A two-factorial repeated-measures experiment was developed for this study. Nine experimental conditions, each lasting 16 minutes, aimed at inducing muscle fatigue in the middle deltoid muscle via intermittent dynamic shoulder abduction and adduction motions at three cycle times (30, 60, and 120 seconds) and three combinations of duty cycles and force levels. The percentage of muscle activation during one cycle (i.e. the duty cycle) varied depending on the exertion intensity (force level) so that the overall mean muscle load remained consistent throughout all experimental conditions, namely at 20% of maximum force exertion. As a result, the three duty cycle/force level combinations were: 0.8/25% of maximum voluntary force (MVF), 0.5/40%MVF, and 0.4/50%MVF. Muscle fatigue development was inferred by changes in peak torque, total work, average power, local Ratings of Perceived Exertion (RPE), and surface electromyographical (EMG) activity (time domain and frequency domain).Two-factorial analyses of variance with Tukey post-hoc tests were used to identify significant condition effects at p<0.05. All dependent measures showed that muscle fatigue was induced by the 16-minute fatigue protocol. Peak torque, total work, average power, and EMG percentage of maximum showed that cycle time and the duty cycle/force level combination had no effect on the development of muscle fatigue, whereas the measures evaluated during the 16-minute fatigue protocol did. The cycle time of 120 seconds induced the greatest change in six of the eight variables, while the duty cycle/force level combination (0.8/25%) also resulted in the greatest effect in six of the measures. Fatigue was also found to be dependent on the interaction of cycle time and duty cycle/force level combination. The conclusion draws from this study is that shorter cycles and activities with short activation periods, and proportionally longer rest breaks result in the lowest fatigue developments.
- Full Text:
- Date Issued: 2018
- Authors: King, Josephine Claire
- Date: 2018
- Subjects: Muscles -- Physiology , Muscles -- Wounds and injuries , Fatigue , Human engineering , Occupational diseases
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63855 , vital:28498
- Description: The negative effects of localised muscle fatigue on accidents, injuries and poor work performance are well known, as is the realisation that modifying task characteristics can minimise fatigue development. A large amount of literature has investigated the effects of task-dependent factors on localised muscle fatigue, most studies have focussed on prolonged or intermittent static (isometric) exertions. Few studies have investigated muscle fatigue development during more complex tasks, namely those which resemble common work activities and which tend to be intermittent and dynamic in nature. More specifically, the interactions between the main intermittent parameters - duty cycle, force level, and cycle time - during dynamic exertions are poorly understood. The purpose of this study was to investigate the effects of cycle time and combinations of duty cycles and force levels on the development of muscle fatigue during submaximal dynamic exertions while the overall mean muscle load was kept constant. A two-factorial repeated-measures experiment was developed for this study. Nine experimental conditions, each lasting 16 minutes, aimed at inducing muscle fatigue in the middle deltoid muscle via intermittent dynamic shoulder abduction and adduction motions at three cycle times (30, 60, and 120 seconds) and three combinations of duty cycles and force levels. The percentage of muscle activation during one cycle (i.e. the duty cycle) varied depending on the exertion intensity (force level) so that the overall mean muscle load remained consistent throughout all experimental conditions, namely at 20% of maximum force exertion. As a result, the three duty cycle/force level combinations were: 0.8/25% of maximum voluntary force (MVF), 0.5/40%MVF, and 0.4/50%MVF. Muscle fatigue development was inferred by changes in peak torque, total work, average power, local Ratings of Perceived Exertion (RPE), and surface electromyographical (EMG) activity (time domain and frequency domain).Two-factorial analyses of variance with Tukey post-hoc tests were used to identify significant condition effects at p<0.05. All dependent measures showed that muscle fatigue was induced by the 16-minute fatigue protocol. Peak torque, total work, average power, and EMG percentage of maximum showed that cycle time and the duty cycle/force level combination had no effect on the development of muscle fatigue, whereas the measures evaluated during the 16-minute fatigue protocol did. The cycle time of 120 seconds induced the greatest change in six of the eight variables, while the duty cycle/force level combination (0.8/25%) also resulted in the greatest effect in six of the measures. Fatigue was also found to be dependent on the interaction of cycle time and duty cycle/force level combination. The conclusion draws from this study is that shorter cycles and activities with short activation periods, and proportionally longer rest breaks result in the lowest fatigue developments.
- Full Text:
- Date Issued: 2018
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