The effect of oral creatine (Cr) supplementation with 20 g/day for 7 days on one-hour cycling performance and metabolism was investigated in a double-blind placebo controlled study. Twenty endurance-trained male cyclists volunteered for the study that was approved by the University of Cape Town ethics committee. The subjects' peak sustained power output was measured and they underwent a familiarization one-hour cycle on a cycle ergometer. Five days later subjects had a muscle biopsy and an indwelling cannula was inserted into a forearm vein before performing a maximal one-hour cycle (T1) during which blood samples were taken at regular intervals. Following the cycle, the subjects each received either Cr or placebo tablets to be ingested four times per day for the following week. After the loading week the subjects again reported to the laboratory, had a muscle biopsy and underwent and the same test routine (T2) with blood sampling as the previous week. Resting muscle total Cr measured by HPLC increased significantly (p<0.001) in the Cr group from 123.0 ± 3.8 mmol/kg dry wt to 159.8 ± 7.9 mmol/ kg dry wt, but was unchanged in the placebo group. The extent of Cr loading was not related to baseline Cr levels (r=0.46, NS). No differences were noted in the resting levels of adenine nucleotides in either group. Analyses of the plasma samples indicated no change in plasma lactate concentration, but a significant lowering of indicators of adenine nucleotide degradation including concentrations of plasma ammonia (p<0.05) and hypoxanthine (p<0.01) in the Cr group from T1 to T2. Plasma urate concentration was significantly lowered (p<0.01) from T1 to T2 but there were no differences between groups. Cr supplementation did not significantly improve performance in the one-hour trial (Cr group: 39.1 ± 0.9 km vs 39.8 ± 0.8 km and placebo group: 39.3 ± 0.8 km vs 39.2 ± 1.1 km). We hypothesised that Cr supplementation affects the purine nucleotide cycle through improved maintenance of low intracellular ADP during exercise as a result of enhanced efficiency of the Cr-PCr shuttle. Cr supplementation had no effect on lactate and carbohydrate metabolism and did not improve performance significantly during a one-hour cycle trial.

This thesis on Exercise Associated Muscle Cramping (EAMC) comprised three individual studies. The aims of this series of investigations were firstly to investigate the nature and prevalence of EAMC in a group of lronman triathletes with a past history of EAMC, secondly to compare the serum electrolyte concentrations in cramping and control Ironman triathletes as well as to record the baseline electromyography (EMG) of cramping lronman triathletes during recovery and thirdly to compare the EMG activity of cramping and control runners before, during and after a fatiguing bout of exercise.

Includes abstract. / Includes bibliographical references (p. 104-115). / The reliability and comparability of results obtained from different methods of assessment has been the source of debate for the last decade. Aim: To investigate the reliability and comparability of measurements of force, velocity and power measured simultaneously during upper and lower body resistance exercises for the following three methods: a) power derived from ground reaction force, i.e. using a force plate (FP), b) power derived from the displacement of the bar, i.e. displacement tracking laser (L) and c) power as a combination of force derived from ground reaction force (FP) and velocity derived from the displacement of the bar (L) (FPL). Methods: 15 Males with a history of resistance training of at least one year participated in the study.

Rugby union has rich tradition in South Africa with the national team having won the Rugby World Cup in 1995 and 2007. The major rugby nations South Africa competes against have clearly defined rugby talent identification (TID) and development (TDE) pathways. These pathways are not as well described in South Africa where the South African Rugby Union (SARU) has adopted a model of identifying talent at an early age through competition. For example, national competitions occur at U13 (Craven Week), U16 (Grant Khomo Week) and U18 (Craven Week and Academy Week) levels. Previous research on talent identification has highlighted the pitfalls of early talent identification. In particular different rates of maturation can influence the manifestation of talent. In a collision sport such as rugby the early maturers have a distinct advantage. An added complexity in the South African context is the need to provide an appropriate development environment within which transformation can take place. At all levels in South African professional rugby, white players dominate team selection. One of the reasons suggested for this dominance is the physical size of white players compared to their black and mixed race (coloured) counterparts. Rugby is a contact sport and physical size is associated with success, so the need to quantify physical difference between racial groups at a junior level over time is important. The first objective of the thesis was to examine the profiles of U18 Craven Week rugby players to gain insight into the development pathway from U13 to U18. A second aim was to understand factors influencing transformation by measuring the physical profiles of the various racial groups over time. The thesis consists of two studies. The specific objective of the first study was quantify how many players in the 2005 U13 Craven Week (n=349) participated in the subsequent U16 Grant Khomo and U18 Craven Week. The study showed that 31.5% of the players who played in the U13 Craven Week, were selected to play at U16 Grant Khomo Week and 24.1% were selected for the U18 Craven Week tournaments. Another interpretation is that 76% of the players selected for the U13 tournament did not play at the U18 Craven Week tournament. The objective of the second study was to determine whether there are differences in body mass, stature and body mass index (BMI) between racial groups in U18 Craven Week players. Another objective was to determine whether these measurements changed between 2002-2012. Self-reported body mass and stature were obtained from U18 players (n=4007) who attended the national tournament during this period. BMI was calculated for each player. The body mass, stature and BMI of these players in South Africa were significantly different between racial groups. For example, white players were 9.8 kg heavier than black players, who were 2.3 kg heavier than coloured players (p<0.0001). The body mass of all groups increased from 2002-2012 (p < 0.0001). White players were 7.0 cm taller than black players, who were 0.5 cm taller than coloured players (p < 0.0001). The stature of players did not change significantly during the study period. The average BMI of white players was 0.9 kg.m⁻² greater than black players who were on average 0.7 kg.m⁻² greater than coloured players (p<0.0001). The BMI of all groups changed similarly over the study period. To conclude, these results question the effectiveness of the u13 tournament in identifying talent and providing an effective development pathway to U18 Craven Week. The SARU also needs to be aware of the ongoing disparities in size between the racial groups playing rugby at an U18 level in South Africa. These size differences may have implications for transforming the game and making it representative of the South African population.

Includes abstract. / Includes bibliographical references. / Several studies have found that the expression of skeletal muscle glucose transporter 4 (GLUT4) is decreased by high fructose consumption but increased by exercise. However, the amounts of fructose used in these studies were extremely high and the effects of moderate feeding protocols are not known. While it is known that exercise enhances GLUT4 expression via increased histone H3 acetylation and binding of the myocyte enhancer factor- 2A (MEF2A) transcription factor to its binding domain on the Glut4 gene promoter, the impact of fructose consumption on this interaction has not been studied. Moreover, there is no direct evidence that an increase in MEF2 binding is due to increased accessibility of the MEF2 binding domain to transcription factors. This study tested the hypothesis that both exercise and high fructose consumption affect GLUT4 expression by altering the accessibility of the MEF2 binding domain on the Glut4 gene promoter via remodelling of chromatin in that region. Male Wistar rats (n=30) were randomly assigned to three dietary groups: a) standard Chow, b) Chow + 10% fructose drink and c) Chow + 10% maltodextrin drink. All rats had access to drinking water and chow ad libitum for a period of 13 days. In the last 6 days of the experiment 5 animals in each group performed 3 x 17 min daily bouts of intermittent swimming, with a load equivalent to 5% bodyweight attached to their tails. The remaining 5 rats from each group were untrained. Animals were fasted overnight on the last day of the experiment, anaesthetized and sacrificed on the morning of day 14. Triceps muscle were harvested and used: (a) for measurement of total GLUT4 content by western blot, (b) to obtain nuclei for assessment of accessibility of a 350bp region encompassing the MEF2 element on the Glut4 gene using nuclease digestion assay, and (c) to measure the acetylation of histones H3 and bound MEF2A in the region above using chromatin immunoprecipitation (ChIP) assay. Blood was also collected and assayed for fasting serum glucose, insulin and free fatty acids.

Previous studies found that individuals with Autism Spectrum Disorder (ASD) tend to demonstrate poor health behaviors, including unhealthy nutrition habits and low physical activity (PA) levels. Growing research suggests the PA can improve ASD-related symptoms and attenuate the mental and physical adverse effects of the COVID-19 pandemic. Unfortunately, the stay-at-home order was put in place because of COVID-19, which negatively affected health behaviors in many individuals with ASD, including an increase in sedentary behavior and screen time and less PA participation. Prior research also has found that young adults with ASD are at a higher risk for obesity than their neurotypical counterparts. Therefore, the purpose of this study was to examine the effects of a 12-week online physical activity intervention on exercise self-efficacy, PA enjoyment, perceived stress, and depression in young adults with ASD. A total of 10 participants (mean age: 26.5, 70% male) completed the exercise intervention, which was accessed through the Zoom platform, and occurred twice a week for 45 minutes. Results revealed a significant decrease in depression levels following the exercise intervention (p=0.03). Although not statistically significant, there was an increase in PA enjoyment following the exercise intervention (p=0.08). There were no statistical differences for exercise self-efficacy or perceived stress. These findings indicate that the remote-based exercise program may help to alleviate depressive symptoms in young adults with ASD. Given that recent research has found that the COVID-19 pandemic has resulted in increased depressive symptoms in young adults with ASD, the use of a remote-based exercise program may have helped to attenuate these symptoms in this population. Future research should examine larger sample sizes and compare effects of in-person vs remote-based exercise interventions.

Post-activation potentiation (PAP) has been shown to improve acute power-based performance, and the potential to enhance rowing performance. To examine PAP effects with rowing performance, 40 collegiate female rowers performed isometric potentiating (ISO), dynamic potentiating (DYN) and typical control (CON) warm-up protocols, after which they completed a three-minute all-out test (3MT) to evaluate their total distance, peak power, mean power, critical power, anaerobic working capacity (W') and stroke rate. Fifteen-second splits for distance and mean power were also analyzed. The PAP protocols were performed on a rowing ergometer, in a movement pattern that simulated rowing. ISO consisted of 5 × 5-second static muscle actions with the ergometer handle rendered immovable with a nylon boat-strap, while DYN consisted of 2 × 10-second all-out rowing bouts, separated by a 2-minute rest interval. A two-way (condition by experience level) interaction was found for distance, mean power and W' with significant differences (DYN > CON; 5.6 m, 5.9W and 1561.6 J) for more experienced rowers ( > 3.75 years; n=19) and no differences for less experienced rowers (n=18). A main effect for stroke rate was found with DYN > CON (1 s/min). Split analysis of mean power output revealed a two-way (condition by 15s split) interaction independent from experience level. Mean power in DYN was significantly greater than CON and ISO in the 15-30, 30-45, 45-60 and 60-75 second intervals. These results suggest that dynamic PAP may be beneficial for experienced rowers and that these strategies might benefit a greater power output over shorter distances regardless of experience. Future studies should investigate potential benefits of this protocol over a full race distance and identify the difference between experienced and less experienced rowers.

Children diagnosed with Autism Spectrum Disorder (ASD) often have increased levels of stress, leading to dysregulated production of cortisol. Elevated levels of cortisol have numerous known adverse health consequences, and therefore, interventions should be established to help attenuate cortisol production. As judo combines physical activity and mindfulness practice, it may aid in stress reduction and decreased levels of cortisol. Purpose: To examine the effects of a 10-week judo program on stress reactions and salivary cortisol levels in youth with ASD. Methods: 20 children with ASD participated in the 10-week judo program. Changes in acute (before and after one judo session) and chronic salivary cortisol levels were assessed at baseline and post intervention. Parents of participants were asked to complete the Stress Survey Schedule (SSS) to determine severity of stress reactions. The SSS consists of 10 subscales: changes, anticipation, unpleasant, positives, food related, rituals, social/environmental, sensory/personal, fears, and life stressors. Sleep quality was assessed via Actigraph GT9X accelerometers over a 7-day period at baseline and post-intervention. Paired samples t-tests were used to determine differences SSS pre/post-intervention. Repeated measures ANOVA was conducted to determine differences and in cortisol levels before and after one judo session and pre and post-intervention. Spearman correlations were used to determine correlations between sleep quality and subscales of the SSS. Results: Although not statistically significant, a trend was noted indicating a decrease in cortisol levels following one judo session (p=.057). Nonsignificant reductions in the subscales "changes (p=.14)" and "unpleasant (p=.12)" of the SSS were also observed. Conclusion: Acute changes in cortisol levels may be seen following one session of judo. Subscales of parent-reported questionnaire may also show improvements following 10 weeks of participation in a judo program.

The aim of this study was to examine the effects of an 8-week judo program on lifestyle habits and behavior in children with Autism Spectrum Disorder (ASD). METHODS: Participants included 25 children (ages 8-17), with a formal diagnosis of ASD. The sample participated in an 8-week judo program (45 minutes, 1x week), with measures taken at baseline and at the end of the 8-weeks. In order to assess activity levels and sleep quality, participants were instructed to wear Actigraph GT9X Accelerometers for 7 days and nights. In order to assess behavioral changes, parents were given the ABC survey to fill out at baseline and post-intervention. Non-parametric paired t-tests were conducted to compare differences in behaviors, MVPA, SB, and sleep quality (i.e. sleep efficiency, total sleep time, number of awakenings, and wake after sleep onset) pre and post judo. RESULTS: Results indicated there was a strong negative correlation (r= -0.632) with inappropriate behaviors and the number of classes attended. Participants also spent a significantly greater percentage of time in daily MVPA (8% vs 4%, p=0.05) following the program. There was a significant increase in total minutes of sleep duration (572.56 vs 333.8, p=0.008) following the program, and although not statistically significant, a trend existed for improved sleep efficiency (92% vs 88%, p=0.1). CONCLUSION: Despite no significant differences in ABC scores pre and post-judo, a strong association between class attendance and lower ABC scores were observed, along with improvements in MVPA and sleep quality. Future studies should include larger samples of youth with ASD, over a longer intervention period.

Multiple object tracking (MOT) is a cognitive process that involves the active processing of dynamic visual information. In athletes, MOT speed is critical for maintaining spatial awareness of teammates, opponents, and the ball while moving at high velocities during a match. Understanding how MOT speed changes throughout the course of a competitive game may enhance strategies for maintaining optimal player performance. The objective of this study was to examine changes in MOT speed and running performance during a 90-minute intermittent soccer performance test (iSPT). A secondary purpose was to examine the relationship between aerobic capacity and changes in MOT speed. Seven competitive female soccer players age: 20.4 ± 1.8 y, height: 166.7 ± 3.2 cm, weight: 62.4 ± 4.0 kg, VO2max: 45.8 ± 4.6 ml/kg/min-1 ) completed an intermittent soccer performance test (iSPT) on a Curve™ non-motorized treadmill (cNMT). The iSPT was divided into two 45-minute halves with a 15-minute halftime [HT] interval, and consisted of six individualized velocity zones. Velocity zones were consistent with previous time motion analyses of competitive soccer matches and based upon individual peak sprint speeds (PSS) as follows: standing (0% PSS, 17.8% of iSPT), walking (20% PSS, 36.4% of iSPT), jogging (35% PSS, 24.0% of iSPT), running (50% PSS, 11.6% of iSPT), fast running (60% PSS, 3.6% of iSPT), and sprinting (80% PSS, 6.7% of iSPT). Stand, walk, jog and run zones were combined to create a low-speed zone (LS). Fast run and sprint zones were combined to create a high-speed zone (HS). MOT speed was assessed at baseline (0 min.) and three times during each half of the iSPT. Dependent t-tests and Pearson correlation coefficients were utilized to analyze the data. Across 15-minute time blocks, significant decreases in distance covered and average speed were noted for jogging, sprinting, low-speed running, high-speed running, and total distance (p's < 0.05). Players covered significantly less total distance during the second half compared to the first (p = 0.025). Additionally, significant decreases in distance covered and average speed were observed during the second half for the sprint and HS zones (p's ≤ 0.008). No significant main effect was noted for MOT speed across 15-minute time blocks. A trend towards a decrease in MOT speed was observed between halves (p = 0.056). A significant correlation was observed between the change in MOT speed and VO2max (r = 0.888, p = 0.007). The fatigue associated with 90 minutes of soccer specific running negatively influenced running performance during the second half. However, increased aerobic capacity appears to be associated with an attenuation of cognitive decline during 90-minutes of soccer specific running. Results of this study indicate the importance of aerobic capacity on maintaining spatial awareness during a match.