The aim of the study was to identify central determinants of V̇O2peak using a 3-year longitudinal evaluation of left ventricular (LV) morphological and functional (global, tissue-Doppler and strain) outcome measures obtained at rest and during both submaximal and maximal exercise in a group of highly trained male youth soccer players (SP) and recreationally active male participants (CON). Once a year for 3 years, measurements were obtained in both the SP and CON groups (12.0 ± 0.3 and 11.7 ± 0.2 years of age, respectively, at the onset of the study). Cardiac ultrasound measures were used to identify LV morphological indices at rest and functional parameters during submaximal and maximal exercise. Training status (P < 0.0001) emerged as the only significant independent predictor of V̇O2peak, when considering LV morphological variables. At maximal exercise, early diastolic filling (E) was a significant (P = 0.001) predictor of V̇O2peak, irrespective of the influence of training status. Training status emerged as the significant predictor of V̇O2peak across all models that were developed in this study. Minimal LV structural and functional adaptations at both rest and exercise influence V̇O2peak, beyond the impact of training status alone. The broader implication of these findings is that the influence of LV cardiac adaptations on V̇O2peak over time is mediated by the stimulus of training; this association occurs independently from the impact of growth and maturation on V̇O2peak
