The influence of maturation on left ventricular remodelling and haematological adaptation with endurance training

Endurance training results in cardiac and haematological adaptations that underpin improvements in cardiorespiratory fitness. These adaptations are well-established in adults, but the adaptive processes are less clear in children. It was originally hypothesised that pre-pubertal training adaptations are blunted due to a lack of growth-related and sex hormones. Left ventricular (LV) remodelling to training has since been shown pre-puberty, although less pronounced, whereas haematological adaptations remain unclear. Importantly, previous studies investigating training-related cardiovascular adaptations have often not quantified maturity, which is crucial given the large interindividual timing of puberty. Additionally, the majority of previous work has focussed on boys, or pooled mixed sex data, making female characteristics impossible to discern. However, if cardiac and haematological adaptations are more pronounced post-puberty, their contribution to maximal aerobic power (V̇ O2max) is likely to increase, similar to adult observations. Also, greater training-related cardiac remodelling with maturity could also lead to greater functional remodelling due to the intricate link between form and function. Therefore, this thesis aimed to assess the influence of maturation on cardiac and haematological adaptations and investigate their contributions to V̇ O2max. A holistic and comprehensive approach was taken to address this aim with the inclusion of both boys and girls, and multiple elements of the oxygen transport chain assessed in both pre- and postpubertal children. The findings show that training-related differences in the LV and haematology are augmented following maturation. Enhanced LV structures after maturity may be driven by expanded circulating blood volumes. These greater central adaptations after maturity explain a larger proportion of V̇ O2max compared with before, despite similar aerobic fitness at each stage. Lastly, the greater LV structures in trained groups after maturity were related to lower systolic LV twist mechanics. Collectively, these findings help to answer historical speculation around the influence of maturation on cardiovascular adaptations to endurance training.