The reproducibility of a measurement in a laboratory test impacts on the power of that test to detect the small, but significant changes in an athlete's performance when determining the influence of a new training or nutritional intervention. Until recently, however, sport scientists have not been concerned with establishing the reliability of many of their testing protocols. Therefore, the purpose of this thesis was to examine the reliability of several laboratory tests of performance and to determine those factors which may impact on the reproducibility of those tests. Possible factors that could contribute to the reliability of a performance test include the type of exercise protocol employed (continuous, intermittent), the equipment on which the subject performs the test, the intensity and duration of the testing protocol, the subject's state of fitness and whether he is familiar with the testing conditions.

Includes bibliographical references. / In periods of prolonged stress and pain from strenuous exercise, the body produces chemicals called endorphins that help it endure pain. These natural analgesics are presumably only released when the level of pain intensity is at least moderately high. The PANIC/separation distress system is built on the same pathways as the physical pain system, and is responsible for the ‘mental pain’ (feelings of panic anxiety, loss and sorrow) that is associated with the loss of an attachment object, or separation from it. Given this overlap, it is reasonable to expect that endorphin release can affect depressive symptoms in a positive way. There is existing evidence that exercise has a beneficial effect on depressive symptoms, yet the underlying physiological mechanism has yet to be properly determined. The purpose of this three-armed prospective randomized control pilot study was therefore to try to establish this mechanism by investigating whether intensive exercise can improve the symptoms of moderate depression as a result of demonstrable increases in plasma &#946;-endorphins. It has previously been established that exercise-induced &#946;-endorphin release correlates positively with the intensity of the exercise. There were two central hypotheses for this study. The first was that the mechanism behind the improvements seen in depressive symptoms due to exercise is the same mechanism that is responsible for the established analgesic effect of exercise, namely endorphin release. The second hypothesis was that only high-intensity exercise (i.e. great that 70 of heart rate reserve) will be sufficient to produce a guaranteed endorphin release, whereas moderate-intensity exercise (just under 50% of the heart rate reserve) and very low intensive exercise would not be sufficient to release endorphins, and would therefore not result in an improvement in depressive symptoms. The main aim was therefore to investigate whether intensive exercise (greater than 70% of heart rate reserve) improves moderate depression, and if so, whether this correlates with a demonstrable increase in &#946;-endorphins. This study therefore wished to determine which of low, moderate or high intensity exercise alleviates the symptoms of depression. It also intended to determine whether an increase in &#946;-endorphins correlates to an improvement in the participants’ depression levels, and whether greater &#946;- endorphin release occurs during high-intensity exercise compared to low- and moderate intensity exercise. Male participants (n = 33) with moderate levels of depression were randomly assigned to one of three experimental groups of varying exercise intensities: High-intensity (160 beats per min (bpm)), Moderate intensity ( 140bpm), and a low-intensity control group (under 120bpm). All participants underwent a six-week exercise program that involved participation for three days per week, for one hour per day (i.e.18 sessions in total). Once weekly, the Hamilton Rating Scale for Depression (HAM-D) and the Montgomery Åsberg Depression Rating Scale (MADRS) were administered to each participant. The participants in the High-and Moderate-intensity exercise groups each had 5ml of blood drawn, once per week, before and after exercise, in order to measure their &#946;-endorphin levels, and to track any changes in these levels over time. The participants in the Control group had blood samples taken twice – once at the start of the study (a baseline measure), before and after exercise, and once on completion of the study, before and after exercise. The results indicate that both Moderate- and High-intensity exercise improved the participants’ depression levels, while the Control group also showed some improvement, but not to the same extent as the other two groups. A significant difference (p = < 0.0001) was found when comparing the initial and final HAM-D scores between all three groups. The participants’ MADRS scores also improved between all three exercising groups. A significant difference (p = 0.0182) was found when comparing the initial scores within each of the three groups to their final MADRS scores. No significant difference was found in the serum &#946;- endorphin levels when comparing the Moderate- with the High-intensity group. The differences between the baseline and post-exercise serum &#946;-endorphin measurements were also not significantly different for both the Moderate- and High-intensity groups (p= 0.953 and p= 0.992 respectively), while the Control’s pre- to post levels decreased significantly (p < 0.017). A significant difference between the Control-, Moderate-, and High-intensity groups (p = <0.022) was found when comparing the three groups’ serum &#946;-endorphin concentrations after they engaged in exercise. Overall, the results of this pilot study go against the hypothesis that only High-intensity exercise would improve symptoms of moderate depression, as both high- and moderate-intensity exercise had a clear positive impact on depression scores. However, consistent with this hypothesis, very-low intensity exercise did not seem to have as beneficial an effect. The mechanism underlying the benefit of exercise on the symptoms of depression cannot be conclusively confirmed given the overall &#946;-endorphin results. A larger sample size and more accurate analysis methods of &#946;-endorphin levels are required in order to test these tentative findings more rigorously.

Endothelial dysfunction is associated with cardiovascular disease risk factors and precedes structural changes in the blood vessels that occur prior to clinical manifestations. Measuring ethnic differences in microvascular endothelial function will provide insight into the disparate cardio-metabolic disease profiles that exist within a multi-ethnic South African population. Moreover, it has been shown that insulin resistance is associated with microvascular endothelial dysfunction in obese persons4, but it is unclear whether this relationship is mediated by body fat in apparently healthy individuals with and without insulin resistance. To our knowledge this has not been done in a South African population. Aims: The overall aim of this thesis was to measure microvascular endothelial function using Laser Doppler Imagery (LDI) and iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) in a multi-ethnic, apparently healthy group to determine whether: 1) there are ethnic differences in microvascular endothelial function and 2) whether the association between microvascular endothelial function and insulin resistance (IR) is independent of body fat in women with and without IR.

Physical inactivity is a well-recognized risk factor for chronic diseases of lifestyle and has been associated with an increased incidence of morbidity and mortality. Current recommendations for the "dose" of physical activity that may be regarded as "protective" for these chronic diseases are 30 minutes or more of moderate-intensity physical activity on most, or preferably all, days of the week. However, when quantifying physical activity, it is not clear which factors influence the reporting of moderate and vigorous activity levels. Even in the literature, there is lack of agreement on the energy expenditure corresponding to so-called 'moderate' and 'vigorous' physical activity. Background (study 1): Self- reported physical activity levels are inversely related to chronic disease risk factors. The strength of this association depends, in part, on quantifying the intensity of activity that may be regarded as 'moderate or vigorous', which may be confounded by individual and cultural perceptions of relative exercise intensity, age, fitness, height, and habitual levels of activity. Aim (study 1): The purpose of this study was to i) examine the individual and group differences in self-selected walking pace corresponding to symptoms used to describe moderate and vigorous intensity and ii) to determine factors that may be associated with these differences. Methods (study 1): A convenience sample of 63 women and 39 men were recruited (N=102). Subjects were asked to walk for six minutes on an indoor track at a pace they regard as 'moderate', rest until heart rate returns to pre-exercise levels, then walk at a pace they consider 'vigorous'. Habitual levels of energy expenditure (EE), maximal oxygen consumption (VO₂max) and% fat were also determined. Results (study 1): Mean self-selected walking pace for moderate activity levels was 5.54 km-h⁻¹ (95% Confidence Interval (C.I.): 5.40; 5.69), and corresponded to 58% of age-predicted maximum heart rate (%HR.max) (95% C.I.: 56; 60). Mean self-selected vigorous pace was 7.03 km·h⁻¹ (95% C.I.: 6.85; 7.20), at 72 % HR.max (95% C.I.: 69; 74). The %HR.max for both moderate and vigorous intensity physical activity fell within the ACSM recommendations (55- 69%HR.max for moderate intensity activities, and 70 - 89 % HR.max for vigorous intensity activities). Multivariate analysis revealed that the factors predicting self-selected walking speed were gender, age, VO₂max, % fat and habitual vigorous EE. The only significant predictor of moderate pace was VO₂max. Education, occupation and habitual moderate EE were not associated with walking speed or intensity. Conclusion (study 1): These results show that subjects could accurately differentiate absolute and relative walking intensities and understood what was meant by the terms 'moderate' and 'vigorous'. However, absolute pace and relative intensity may vary according to differences in gender, fitness, age, height, body fat% and habitual levels of vigorous activity. These factors are important to consider when prescribing exercise using descriptors such as "moderate" and "vigorous". Background (study 2): None of the various methods used to measure habitual physical activity in the general population have proven entirely satisfactory in terms of reliability and accuracy. A major problem is that no "gold standard" exists for the validation of various questionnaires that can be used in large sample population studies. Ongoing efforts to improve the validity and reliability of the measurement of physical activity by self-report will enable cross-cultural and international comparisons to examine secular trends. Aim (study 2): The second part of this study assessed the validity and reliability of a recently developed International Physical Activity Questionnaire (IPAQ) which was interviewer-administered in both a short and long version, and queried activity performed in a "usual" week. Methods (study 2): Urbanized subjects (N = 82) were selected from a wide range of educational, activity level and socio-economic backgrounds. The long version IPAQ was designed to quantify the average weekly time and energy expenditure spent in occupation, transport-related activities, household chores, and leisure time activities. The short version IPAQ was designed to measure total weekly moderate, vigorous, walking and sitting related activity. Test-retest reliability was reported as the intra-class correlation between calculated time and energy expenditure (METmin·w ⁻¹) in different questionnaire items determined from three IPAQ administrations. Validity was assessed using biometrical and physiological parameters as criterion measures (Computer Science and Applications. Inc. activity monitor counts, body mass index, estimated VO₂max, % fat). Results (study 2): Test-rest reliability coefficients for the long IPAQ ranged from r = 0.38 tor= 0.75, with the highest correlation coefficients obtained in work related activities, and the lowest in household chores. Test-retest reliability in the short IPAQ ranged from r= 0.32 tor= 0.71, with the highest correlations obtained for sitting and the lowest for total moderate activity. Criterion validity for CSA counts and total physical activity in the long IPAQ was r = 0.50 (P < 0.001), for CSA counts and total vigorous activity r = 0.35 (P < 0.01), and for CSA counts and total job activity r = 0.51 (P < 0.001). Measurement of reliability and validity in this South African population compared favourably to physical activity questionnaires used in other population studies. Conclusion (study 2): The IPAQ provides a relatively valid and reliable estimate of physical activity in this population. In evaluating the relationship between physical activity and morbidity, it is important to consider the accuracy and reliability of the tool used to measure self-reported activity. Failure to show an association may represent a real phenomenon, or may simply reflect the inability of the physical activity questionnaire used to detect true physical activity levels.

Includes bibliographical references. / Introduction: Our circadian rhythms are internal biological rhythms of approximately (circa) 24 - hours (dies) allowing us to synchronize our internal biological “clock” with external time cues. Many innate biological functions are dependent on time-of-day, such as secreting adrenaline and cortisol in the mornings and melatonin in the evenings. The time-of-day at which these and other physiological functions are active, change or reach a certain level may influence a person’s diurnal preference, i.e. preference for mornings (morning-types) or evenings (evening-types), and is referred to as ‘chronotype’. Many different factors may affect a person’s chronotype, including age, sex, physical activity, ethnicity and geographical location. Certain clock-related genotypes have also been shown to be associated with chronotype. For example, some studies have found that the 5-repeat allele of the PER3 variable number tandem repeat (VNTR) polymorphism (PER35) is associated with a preference for mornings. Recent research has shown a high prevalence of morning-types and PER35VNTR allele carriers in trained South African runners, cyclists and triathletes. It was proposed that the early morning start-times of these endurance events might select people with a preference for mornings, since morning-types may cope better with rising early and being physically active in the early morning. Alternatively, the habitual early waking for training or endurance events may have conditioned the athletes to adapt to become morning-types. However, the geographical location of South Africa (i.e. climate and day length) and the fact that each group was physically active may also have contributed to this finding. Comparison of South African and Dutch runners would allow us to explore the effects of race start time and geography on this observation, since marathons in The Netherlands on average start at 11:41, and since the two countries differ significantly in latitude and as such have noticeable differences in daylight exposure. Aims: The aims of this study were 1) to compare the PER3VNTR genotype and chronotype distribution of South African and Dutch recreational marathon runners and active but non-competitive controls; 2) to investigate the relationship between the PER3VNTR genotype and chronotype in both the Dutch and South African samples; and 3) to determine whether marathon race time is associated with chronotype and PER3VNTR genotype in Dutch and South African marathon Methods: Ninety-five trained South African male marathon runners, 97 South African male active but non-competitive controls, 90 trained Dutch male marathon runners and 98 Dutch male active but non-competitive controls completed a questionnaire capturing demographics, training and race history, including personal best and most recent full and half-marathon race time (if applicable) and the Horne-Östberg morningness-eveningness personality questionnaire (HÖ-MEQ, a tool to assess a person’s chronotype). Each participant provided a buccal cell swab from with total genomic DNA was extracted to determine his PER3VNTR polymorphism genotype. The official race time from each runner who completed the designated marathons in South Africa or the Netherlands was collected from the event websites. Results: The South African and Dutch runners were more morning-orientated than their respective control groups and the South African runners were more morning-orientated than the Dutch runners. The PER3 VNTR polymorphism distribution was similar between the four groups and was not associated with chronotype. The marathon performance of the morning-type South African runners was better than the evening-types, and a higher HÖ-MEQ score (morningness) correlated with better personal best and most recent half-marathon race time. Similar observations were not found in the Dutch runners. Discussion: Since a higher prevalence of morning-types in South African marathon runners compared to Dutch marathon runners was found, it is proposed that the early marathon start-times in South Africa may favour morning-types, who are able to cope with those early morning start times. Alternatively, one could argue that through repetitive early-morning racing (i.e. participating in competitive running events), the chronotype of South African runners may be conditioned to that of a morning-type over time. It is proposed that this ability to cope with early morning marathon start times may lead to better marathon performances for morning-types than neither-types and evening-types in the South African running group. This effect does not occur in the Netherlands, where marathons start later in the morning and do thus not favour a certain chronotype. The difference in daylight exposure between the two countries as a function of latitude does not seem to affect chronotype, since the active but non-competitive control groups did not differ significantly between South Africa and the Netherlands. Unlike the findings from a previous study, the PER35allele was not more prevalent among the South African runners, but rather the distribution wasi n line with what has been described in most, but not all, other populations. No association between the PER35VNTR xpolymorphism and chronotype was found in any of the four groups. Since the four groups investigated in this study comprised physically active individuals, it is proposed that this lack of association may be due to the habituation effects of physical activity and early morning start times of marathon events(for only the South African runners). Conceivably,this habituation may even shift the diurnal preference of those with the PER34/5 and PER34/4VNTR genotypes towards morningness, disassociating any relationship between chronotype and the PER3VNTR genotype. Conclusion: The early morning start time of South African marathon events may favour morning-types, due to their ability to cope with being physically active in the early morning. We propose that the PER3VNTR genotype cannot solely explain the higher prevalence of morning-types in the South African runners in this study, however, it is very likely that the PER3VNTR genotype does play an important role in the chronotype distributions found in the study of Kunorozva et al.(2012). Since the PER3VNTR genotype was not associated with chronotype in any of the four groups, it is proposed that habituation to early-morning marathon racing may be the causal effect of the high number of morning-types in the South African runners group, and the apparent disassociation between chronotype and the PER3VNTR genotype. We also propose that the habituation effect of physical activity and training time-of-day on chronotype in the other groups may dissociate the PER3VNTR genotype with chronotype in a similar manner to which the early-morning start times of South African endurance events dissociates the two. No effect of geographical location on chronotype was found when comparing the Dutch and the South African groups. The morning-orientated South African runners seem to perform better in marathon running than the more evening-orientated runners do, which may be caused by their ability to cope with these early-morning marathon events. Further studies may explore whether marathon performance in later chronotypes can be improved by training-based habituation.

Previous studies have been conducted to determine the incidence of low back pain (LBP) in both the general population as well as in participants of different sporting activities. The purpose of this study was to determine the seasonal and lifetime incidence of LBP in male first league squash players.

Includes abstract. / Includes bibliographical references (leaves 42-58). / Mental performance consists of cognitive components, such as memory capacity, motor function, or decision making, and psychological components, such as personality traits, psychological well-being, or coping strategies. While certain personality traits have been shown to be associated with specific strengths and weaknesses in an individual’s cognitive abilities only few studies have been done to investigate this relationship in athletes. Our study therefore aims to investigate the correlations between certain personality traits and cognitive performance in a sample of elite hockey players. 25 male athletes completed the ‘WebNeuro Sport’ assessment by the Brain Resource Company.

Bibliography: pages 143-154. / Exercise intolerance is well documented in patients with chronic obstructive pulmonary disease (COPD). Historically, this exercise intolerance has been attributed to the central factors of lung damage and subsequent heart failure. However, recent evidence suggests that (i) patients with cardiac and renal failure suffer from skeletal muscle (SM) abnormalities that impair exercise tolerance and (ii) patients with chronic obstructive pulmonary disease (COPD) may have metabolic and functional abnormalities of SM. However, no studies have conducted a detailed investigation of SM structure and function and their relation to exercise tolerance in patients with COPD.

Rugby union is a popular sport worldwide, and due to the professional nature of the sport the demands on players continues to increase, resulting in acute and chronic fatigue. The aims of the study were to investigate the tools used to monitor and predict changes in training status and determine the effectiveness of these to: (i) measure the subjective nature of coaches and their selection relating to the players’ performance, and (ii) to use performance indicators to correlate to team performance. The University of Cape Town Rugby Varsity Cup Team (First XV squad) were monitored from their pre-pre-season until the end of their competitive season. Players completed a testing battery (anthropometry, strength, muscular endurance, speed and aerobic fitness) during the season, along with Rating of Perceived Exertion and body mass was recorded every practice. Players also completed the HIMs test (measure of heart rate recovery) weekly. Coaches rated players every practice on three variables and the matches were recorded and video analysis performed to determine key performance variables. Most of the players improved in their testing battery between pre-pre-season and pre-season. Average session load varied across the phases of the season and was highest in the pre-preseason. Change in load however, was not reflected by changes in heart rate recovery which remained relatively stable across the season. The players’ body mass varied throughout the tournament, with certain players having a larger coefficient of variation compared to others. There was no relationship between performance in the testing battery and selection for matches. The coaches all had different ratings for the players, with no correlation between players selected and those not selected. There was a correlation between the subjective rating of players in the week leading up to the match and the match ratings of Coach 3 (head coach). The Varsity Cup rugby union players followed similar trends described in previous literature in physiological testing batteries, training loads and player management. The novel aspect of this study was the collection of data from the coaches involved. This qualitative data provides insight into the coaches’ selection process or lack thereof within a team environment. The data also illustrates the differences between the coaches’ interpretation of the players’ “performance”. The Varsity Cup is a relatively young tournament and should be further investigated to properly understand the differences between it and professional and amateur rugby union.

Includes abstract. / Includes bibliographical references. / A single governing body to govern South African rugby was formed in 1992. This allowed for changes to governmental policies to South African sport, resulting in South African sport being fully representative of the population. The South African Rugby Union (SARU) therefore has a continual challenge to make rugby fully representative at both provincial and national levels. Previously rugby has been dominated by white players at all levels. The SARU has implemented various programmes in order to accelerate the development of players of colour. Previously the success of these programmes has not been evaluated because the players representing different ethnic groups have not been quantified in a systematic way. The aim was to quantify playing time and playing numbers of South African professional rugby players of different ethnic groups from 2007 to 2012 at all professional levels (Springboks, Super Rugby, Currie Cup and Vodacom Cup). Quantifying playing time and playing numbers was done to establish changes in profile of South African rugby players across the given time period. Thus the efficacy of the SARU programmes to accelerate transformation was indirectly evaluated. A further aim was to determine if there had been a change in ethnic profiles between the various rugby unions from 2007 to 2012.