The influence of training status on the physiological responses to exercise of young girls

Exercise training represents a potent stimulus to the parameters of aerobic and anaerobic fitness in adults; whether the same is true in young girls is unclear. For some parameters, such as peak oxygen uptake, the influence of training status remains controversial whilst for other parameters, such as oxygen uptake kinetics, the influence of training status remains simply uninvestigated in young girls. Despite this lack of empirical evidence, it has been suggested for some time now that children may lack trainability and that this may be related to the presence of a maturational threshold below which significant adaptations to training cannot occur. This suggestion requires investigation, not least because the findings of some studies which appear to support this contention may in reality be a reflection of the use of an inappropriate test modality for the investigation of training status influences. The purpose of this thesis was therefore to determine the physiological trainability of girls at different stages of maturation and to investigate the interaction between training status, maturity and exercise modality. To achieve this purpose a series of 5 studies was completed, in which trained and untrained girls completed ramp incremental exercise, constant-work-rate exercise and Wingate exercise on two exercise modalities, one upper (arm crank) and one lower body (cycle). During these tests, cardiovascular, respiratory, metabolic and mechanical power parameters were assessed. In response to ramp incremental exercise, trained girls were shown to have a higher peak VO2, SV and Q& at all stages of maturity, along with an altered SV and fractional muscle oxygen extraction pattern, irrespective of exercise modality. The importance of exercise modality was evident during heavy intensity constant-work-rate exercise in pre-pubertal girls, where training status was only associated with significant influences on VO2 kinetics (faster phase II time constant in trained girls) during upper body ergometry. In contrast, pubertal trained girls had faster VO2 kinetics during both exercise modalities, an influence which may suggest both central and peripheral adaptations to the delivery and utilisation of oxygen. Exercise modality was also revealed to be an important factor in the demonstration of training status influences during a 30 s Wingate test, with trained girls at all stages of maturity exhibiting higher mechanical power indices during upper body ergometry only. An influence of training status was also evident in the lower fatigue index found in the trained girls at all stages of maturity during both modalities, but no influence was found in the oxidative contribution to the Wingate test. None of these studies revealed an influence of maturity status in determining the magnitude of training status effects. Overall, the 5 studies encompassed within this thesis demonstrate that children are trainable and that this is not moderated by maturity. Acknowledgements First, to my supervisors, Professor Andy Jones, Dr Jo Welsman and Dr Ann Rowlands, I would like to express my gratitude for their extensive knowledge, support and patient guidance. Circumstance meant I had the privilege of working with three supervisors, each of which has inspired and taught me so much, not least the diverse ways in which to supervise! I would also like to thank Dr Kerstin Stoedefalke for her enthusiasm and encouragement and who presented me with the opportunity to undertake this PhD. I am indebted to all the volunteers who helped me during the long months (/years! ) of testing, both those who completed the tests and those who helped in their implementation. With regard to the latter, I owe a special thanks to Rebecca Willcocks, who gave up her time selflessly to help me conduct, and recover from, my testing. Her friendship is the reason I have a thesis to present. Finally, my deepest gratitude goes to my parents and my newlywed husband, Stuart. No words are adequate to express the amount I owe to your unwavering love, encouragement and belief. To each I owe this thesis.