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Background: Despite an increased research interest in eating disorders in sport, more questions than answers still remain regarding the relationship between sports participation and risk for eating disorders. However, the use of sport specific terms such as Anorexia Athletica and the Female Athlete Triad are acknowledgement that participation in high performance sport can be high risk for certain athletes. Given the serious health implications and high mortality rate associated with eating disorders, the aim of this thesis was to address key unresolved issues in the area. Objectives: The main aims were threefold. The primary aim was to establish the prevalence rates of eating disorders in elite international female athletes and in athletes from different cultural backgrounds. Secondly, given the inconclusive findings regarding the influence of level of competition on risk for eating disorders, prevalence rates were examined in females across the physical activity spectrum. Finally, an exploratory model was devised in an attempt to explain the pathway to eating disorder development and maintenance in elite female athletes. Findings: The key findings that emerged for the two main investigations suggest that the risk for disordered eating in elite athletes is high. The prevalence rate of clinical eating disorders in the exercise group and non-sporting student sample was found to be comparable to those reported for the general population. The model presented in thls thesis highlights the importance of looking beyond one causal explanation for eating disorder development in female athletes. It suggests that there may be several reasons for eating disorder development in sport, of which one is the heightened focus on weight. The dominance of the sociocultural explanation of eating disorder development may have limited our ability to fully establish why certain athletes may be placed at high-risk of eating disorders.

Considerable variability exists between people in their health- and performance-related adaptations to training. The variability is usually ascribed 1 to genetic diversity, but there are also mechanistic explanations that are often overlooked. The work described in this thesis examined factors (non-genetic and genetic) that contribute to inter-individual variability in endurance-phenotypes and responses to endurance training.

The main intent of the work described in this thesis was to gain further insights into factors that affect performance during endurance exercise with particular emphasis on exercise in the heat. Five different studies are reported. The two first studies (Chapters 1 and 2) assessed the role of skin temperature modulating the negative impact of high ambient temperature. In Study Ia cap was developed that cooled the top of the head. The results showed, however, that cooling the top of the head had no effect on performance during a simulated cycling time trial conducted in the heat (35°C), despite the fact that the cold stimulation was effective in blunting prolactin secretion during exercise. In Study 2 the effect of body heating on the ratings of perceived exertion (RPE) was assessed during a short sub maximal exercise test in the heat. Body heating significantly increased RPEs from the start of exercise whereas it had no effect on thermal comfort. Cold stimulation of the face counteracted the effect of body heating on RPEs. Studies 3 and 4 (Chapters 4 and 5) explored the effect of high ambient temperature on the capacity to perform during subsequent exercise. A repeated exercise paradigm was used in Study 3. The results showed that, after a 2-h recovery, fatigue occurred earlier during a second bout of exercise in the heat (35°C) occurred earlier than in the first bout of exercise performed at the same ambient temperature. No changes in thermoregulation, plasma glucose, lactate, IL-6, prolactin or cortisol were seen that could explain the earlier fatigue onset. It was thought that exercise in the heat might affect hypothalamic neuroendocrine function and this was tested in Study 4 by conducting an insulin challenge 2h after either rest or strenuous exercise in the heat. However, no differences were seen in the magnitude of plasma prolactin and cortisol responses to acute hypoglycaemia. However, previous exercise in the heat increased reactivity of the autonomic innervation of the heart during the insulin test, as assessed by shifts in the power spectra of the R-R interval. The final study (Chapter 6) examined a possible mechanism for the ergogenic action of caffeine during prolonged exercise. Baclofen, a -aminobutyric acid B (GABAB) receptor agonist, was coingested with caffeine as a means of preventing the presumptive release of brain dopamine. The results, however, failed to demonstrate any effect of baclofen preventing the ergogenic effect of caffeine.

Athletes have consistently tried to gain a competitive edge over each other throughout the history of sport. Advances in genetics suggest that this will be one source of such an edge in the future. The World Anti-Doping Agency has decreed that so-called 'gene doping' is impermissible. In this thesis, I will argue that this approach is premature; I offer a case for the inclusion of genetic enhancements in sport. The explication will be made within a virtue consequentialist moral framework linked to a MacIntyrean understanding of social practices. Having dealt with minor initial objections, possible problems for society, and concerns about the impact on sport, I will show why the inclusion of the innovation would be beneficial to sport. The main positive result will be the possibility for a deeper engagement with the practice for a longer period of time thus enabling more goods internal to the practice to be realised. These internal goods have a major bearing on the positive consequences associated with sport and will justify the permiss.ibility of using genetic enhancement technology.

Professional jockeys are unique amongst weight-making athletes in that they are required to make-weight daily, and compete at different weights. Additionally, jockeys are unique in that they are required to be weighed both pre- and post-competition. Amongst the most common methods to reduce body-weight are acute and chronic dehydration and food deprivation. Such practices are suggested to be detrimental to the general health of jockeys. In Chapter 4, an assessment of the physical and mental health of 37 GB professional jockeys (19 Flat jockeys and 18 Jump jockeys), was undertaken and comparisons with clinical norms and between groups were made. This was the first time that such a study had been undertaken. Impaired markers of bone health, inadequate dietary practices including low micronutrient status, and abnormal mood profiles were identified in both groups. Additionally, Flat jockeys displayed significantly poorer bone density (p<0.01) and mood-state (p<0.05) than Jump jockeys. Both jockey groups also displayed higher percentage body fat than in other athletic groups, which demonstrated that there was scope to reduce body-weight which could in-turn negate the need to starve and/or sweat. In Chapter 5, the energy expenditure (EE) of simulated race-riding was measured in 9 Jump jockeys, and the daily EE was assessed in 8 Jump jockeys, on a non-race-riding day. Additionally, the daily energy intake (El) of 8 Jump jockeys was also analysed. Previously, these data were unknown. Simulated race-riding EE was mean (± SO) 0.20 MJ ± 0.03. Daily EE was 11.26 MJ ± 1.49 and daily EI was 7.24 MJ ± 0.92 that largely consisted of two main meals. These data demonstrated that jockeys displayed sporadic eating patterns with large gaps observed between food consumption, and given the daily EE that such eating habits may not be necessary, in order to make minimum weight. In Chapter 6, the effects of a 2% reduction in body-weight through rapid weight-loss (RWL) was measured in 8 jockeys (6 Jump jockeys and 2 Flat jockeys) on physical and cognitive performance. This body-weight reduction was induced by exercising in a sweat-suit (a common weight-making method used by jockeys). To date, these data were previously unreported. Maximal riding performance and chest and leg strength were significantly reduced (p<O.05) following RWL, although simple reaction-time was not. Given the occupational risks associated with race-riding, these data suggested that jockeys, who undergo even moderate reductions in body-weight through RWL, were potentially increasing these risks by compromising strength and performance. In Chapter 7, a scientifically devised dietary and exercise prescription was implemented over a 9-week period with a 22 yr-old male Jump jockey, to make minimum racing-weight that did not rely on previous habitual practices. Body-weight reduction of 8 kg over the 9-wk period was observed and achieved without food deprivation and dehydration. This was the first time that such a study had been conducted on a professional jockey. Throughout the intervention the jockey ate 6 regular meals daily and remained euhydrated with mean (± SO) 285 m.Osmo1.kg-1.bw ± 115 urine osmolality. GB jockeys demonstrate impaired markers of both physical and mental health which appear largely attributable to their habitual weight-making practices. These data suggest that Flat jockeys who are required to make significantly lighter racing-weight(s) than Jump jockeys, display the poorer markers. The daily EE of jockeys would suggest that food deprivation and sporadic eating (common methods) observed in food diaries are not necessary. Additionally, ~WL induced by sweating (another common method) impairs physical performance in Jockeys, which potentially increases the occupational risks associated with race-riding. Given the body-fat percentages observed in jockeys here, RWL may also not be necessary. As demonstrated, an alternative diet and exercise plan can be undertaken to safely make minimum racing-weight without relying on current weight-making methods that have been demonstrated in these studies to impair both health and performance in G8 jockeys.