Includes bibliographical references (p. 244-259) / It is likely that masters runners may experience an intolerance to exercise primarily due to the age-related changes in their bodies, and specifically of those systems and organs most utilised during running. A more disturbing phenomenon, however, is that of younger runners becoming exercise intolerant. One study described exercise intolerance in athletes who were only 40 +/- 10 years old. The muscle of these athletes had greater levels of markers of structural pathology and showed evidence of having undergone more regeneration compared to age- and mileage-matched apparently healthy athletes. The authors attributed their intolerance to exercise to their large volumes of endurance training and racing which compromised their skeletal muscle. Therefore, the objective of this thesis was to examine the effects of chronic exposure to endurance running on the athlete, with particular emphasis on skeletal muscle.

Includes bibliographical references. / Clinical evaluation of the injured runner requires identification and correction of the multiple factors commonly implicated in running injury. Effective management of running injuries requires that the concerned health professional identify all implicated factors. In this regard it is essential that the relationship between running style and injury he determined, because if there is an association between the gait analysis variables descriptive of running style and injury, these would be important in the management of the injured runner. The Gait Analysis Laboratory at the Sports Science institute of South Africa and the University of Cape Town with its three-dimensional Vicon 370 motion analysis system and Advanced Medical Technology industry® strain gauge force platform is appropriate for collecting data to study running style. These data include the movement patterns and estimated mechanical power and work required to effect the observed movement of the ankle and knee. The forces applied by the supporting surfaces on the runners were collected. The data captured with the Workstation® programme (Oxford Metric, Oxford, England), was processed with GaitLab® (Kiboho Publishers, Cape Town, South Africa), collated in Excel ® (Microsoft Corporation, Redmond, USA) and statistically analysed (StatSoft, Inc. (2000). STATISTICA for Windows [Computer program manual]. Tulsa, OK, USA). In this thesis a series of studies are presented with the aim of determining the relevance of running style to the assessment of the injured runner and the conventional treatment methods used to treat common running injuries.

Bibliography: leaves 139-178. / Induction of tumor differentiation through manipulation of regulatory genes is a relatively unexplored area of cancer therapy, however, it might suggest and additional approach for tumour-specific treatment. Therefore, in view of this idea, the present study hypothesized that neuroblastomas (NBs) and pulmonary neuroendocrine tumors (NETs), which are neoplasms of neural origin, are molecularly different based on their expression of regulatory genes and that exposure to extrinsic factors will alter their growth potential. Using reverse-transcription polymerase chain reaction (RT-PCR) analysis, the present study compared the expression of about 50 regulatory genes that are expressed at early stages of neurogenesis in five human NBs and NETs, also upon GDNF/TGF-β1 and retinoic acid (RA) treatment. According to our results, individual NBs and NETs reflected a certain stage of neural development characterized by their expression of discrete sets of regulatory genes.

Includes abstract. / Includes bibliographical references (p. 173-214). / Overweight, obesity and declining levels of physical fitness have been identified as a problem in many developed countries (1). More recently concern has been raised as a result of the rapid increase in the prevalence rates of overweight and obesity in developing nations ((2); (3); (4); (5)). However, little information is available at a national level for South African primary school children. In this thesis, the current nutritional status and baseline measures of physical fitness are established for a large and representative sample of South African primary school children from a range of ethnic and socioeconomic groups. Interactions between nutritional factors and physical fitness are also considered.

Includes bibliographical references (p. 231-279). / It is generally accepted that a linear relationship exists between heart rate/ workload and oxygen consumption and that heart rate thus accurately reflects workload and exercise intensity. As such, coaches and athletes commonly use heart rate to prescribe exercise and monitor changes in training status. Some studies have however, indicates that heart rate may not always be an accurate indicator of training status under all conditions, due to the possible influence of other variables. However, as measuring heart rate has been shown to be a reliable, accurate, inexpensive and practical method to monitor changes in training status, the purpose of this study was therefore to further explore ans clarify the heart/ workload relationship under a variety of different trainig and testing conditions.

Includes bibliographical references (leaves 200-220). / The main aims of the series of studies comprising this thesis were to investigate the effect of altered endogenous carbohydrate (CHO) availability, achieved primarily by pre-exercise dietary manipulation and antecedent exercise exposure, on interindividual variability in metabolic and hormonal responses to dynamic, steady-state exercise. Further, this thesis examined the impact of altered blood glucose availability on fatigue development during prolonged exercise. In this regard, it was hypothesized that endogenous CHO availability and the associated metabolic sequelae would impact on effort perception during exercise and fatigue development.

Includes bibliographical references (p. 235-243). / The aim of this thesis is to evaluate both abnormal and normal fluid balance during exercise. The central theme permeating all investigations is an underlying desire to understand exercise-associated hyponatremia. This thesis reflects a journey of scientific investigation primarily launched by outcomes from the 1st International Consensus Development Conference on Exercise-Associated Hyponatremia. Each individual investigation directly follows from the results of the previous investigation. Hence, the journey towards a greater understanding of exercise-associated hyponatremia went full circle and ultimately encompassed the spectrum of fluid regulation and dysregulation during exercise. This thesis begins with a brief overview of the literatur which services to intertwine previous knowledge with new knowledge gained from each successive study. A review of the literature on exercise-associated hyponatremia opens the first chapter and lays the foundation for the follwoing eight investigations. This thesis closes with a final summary of the literature which defends fluid balance physiology as the ultimate guide for developing more "physiologically appropriate" fluid replacement strategies. More specifically, the first two chapters document the abnormal regulation of serum sodium concentration during exercise.

Includes abstract. / Includes bibliographical references (p. 221-240). / Current evidence indicates that schoolboy cricketers are at a high risk of injury to the lumbar spine. This is particularly relevant in the case of fast bowlers who bowl with a high degree of shoulder counter-rotation. There, however, is a lack of evidence in the literature with respect to injury research of all cricketing disciplines, as fast bowlers receive the most attention. After reviewing the literature it was evident that the effect of a cricket-specific lumbar stabilisation exercise intervention in an attempt to reduce lower back pain and alter other physiological variables, had never been studied. Previous interventions in cricketers have focused only on fast bowlers in an attempt to decrease the degree of shoulder counter-rotation. However, these studies either took two years to observe a decrease or were unsuccessful.

Includes abstract. / Includes bibliographical references. / Ingestion of a high carbohydrate (CHO) diet (7-10 g CHO/kg body mass) for 3 days, typically referred to as ‘CHO-loading’, is a commonly recommended dietary practice for endurance sporting events lasting >90 minutes. CHOloading effectively maximizes muscle glycogen stores and has been shown to enhance prolonged exercise performance. However, the body’s glycogen stores are limited, therefore a dietary strategy that would not only increase CHO availability but also ‘spare’ muscle glycogen during exercise may be more beneficial during prolonged exercise compared to a standard CHO-loading diet. Preliminary studies in which athletes ingested a high fat diet (4-4.6 g fat/kg body mass) for 5-6 days followed by 1 day of CHO-loading have been shown to increase fat oxidation and ‘spare’ muscle glycogen during prolonged exercise compared to a high CHO diet. However, the effectiveness of a high fat diet followed by CHO-loading has not been tested in self-paced endurance and ultra-endurance events. Further, there is little available evidence concerning the pre-event habitual dietary practices of ultra-endurance athletes. It is possible that athletes and cyclists competing in endurance and ultra-endurance events have diets which may differ in macronutrient content compared to that typically recommended for endurance events. As a result, athletes may not respond in a similar way to diets typically recommended for endurance and ultra-endurance events, such as CHO-loading. The aims of this thesis were therefore: (1) to characterize the habitual dietary intakes of sub-elite male cyclists before and during an ultra-endurance event; (2) to investigate the effects of different dietary strategies aimed at increasing carbohydrate availability and ‘sparing’ muscle glycogen (e.g. CHO-loading and fat-adaptation), on substrate utilization and exercise performance during simulated endurance and ultra-endurance exercise; and (3) to investigate the individual responsiveness of athletes to these dietary strategies.

Includes bibliographical references. / Prospective motion correction methods using an optical system, diffusion-weighted prospective acquisition correction, or a free induction decay navigator have recently been applied to correct for motion in diffusion tensor imaging. These methods have some limitations and drawbacks. This article describes a novel technique using a three-dimensional-echo planar imaging navigator, of which the contrast is independent of the b-value, to perform prospective motion correction in diffusion weighted images, without having to reacquire volumes during which motion occurred, unless motion exceeded some preset thresholds. Water phantom and human brain data were acquired using the standard and navigated diffusion sequences, and the mean and whole brain histogram of the fractional anisotropy and mean diffusivity were analyzed.