Examining the reproducibility of the observed cardiorespiratory fitness response to standardized training

Abstract

There is considerable heterogeneity in observed cardiorespiratory fitness (CRF) responses to standardized training. Evidence from twin and family training studies demonstrates a strong link between an individual’s genetics and the observed CRF response to standardized training, supporting the hypothesis that true individual differences in training responsiveness exist. If true individual differences do exist, it would be reasonable to speculate that the observed CRF response to an initial period of training would predict the observed response to an identical period of training separated by an adequate washout period. Thus, the current training study exposed a group of 14 recreationally active males to the same four-week treadmill running training program twice, separated by a three-month washout period. Baseline CRF at training periods one (PRE1) and two (PRE2) were very strongly correlated (r = 0.94, p < 0.01) and were not significantly different at the group level (p = 0.056). A significant main effect of time (PRE vs. POST) (p < 0.001) and period (training period one vs. training period two) (p < 0.001) were observed for CRF (training period one: +4.04 ± 2.29 mL/kg/min, training period two: +2.83 ± 2.74 mL/kg/min) with no significant interaction effect (p = 0.13). At the individual level, the observed CRF response in period one did not predict the response in training period two (r = 0.4, p = 0.15). The results from this study suggest that either true individual differences in training responsiveness do not exist or that random within-subject variability and technical error mask the ability to detect individual differences. Future training studies should examine potential combinations of behavioural/environmental factors, which may influence the observed CRF response to standardized training.