Investigating the effect of sex, maturity, training status, and physical activity on performance and health-related parameters in children, adolescents, and adults

Abstract

In 2018, 48% of young people in Wales engaged in sport ≥3 times a week. However, questions remain regarding the influence of sex and maturation on aerobic and anaerobic trainability. Indeed, many earlier studies failed to appropriately account for physical activity (PA), confounding the interpretation of training per se. Moreover, there is a paucity of literature examining the long-term effects of training. Chapter 4 revealed that, irrespective of maturity, trained youth had a higher maximal oxygen uptake (V̇ O2max) than their untrained counterparts but, importantly, the magnitude of training-related difference was higher in girls than boys. Given the well-established sex-differences in the decline of PA levels with age, Chapter 5 explored the role of PA on V̇ O2max using compositional analyses. This demonstrated that, for the same change in PA, girls had a greater predicted change in absolute, and scaled, ̇ O2max. As the trainability, and kinetic determinants, of sprint performance have received little attention compared to aerobic fitness in youth, this was explored in Chapters 6 and 7. In Chapter 6, training was associated with a greater peak power and force, depending on maturity, with only post-pubertal participants demonstrating significant increases in performance. Using a repeated sprint protocol, mechanical efficiency was found to be more important than absolute force production for performance in Chapter 7, highlighting key training targets. Finally, using a narrative review and meta-analytical approach, Chapter 8 found significant inter-sport differences in all-cause, cardiovascular disease, and cancer mortality in former elite athletes, suggesting that sport type influences the long-term effects of training. Overall, this thesis highlights the distinct determinants of aerobic and anaerobic performance, with sex and maturity exerting different, and independent, effects. Moreover, the paucity of data available in girls was highlighted, with conclusions regarding the long-term effects of training in females largely precluded.