Does True Inter-Individual Variability Exist in Individual Responses After Endurance Training?

Abstract

Introduction: Despite the apparent existence of individual responses, it remains unknown whether the variability observed in peak oxygen consumption (VO2peak) and work rate at onset of blood lactate (OBLAWR) response following exercise training reflects true inter-individual differences. To date, few studies include a non-exercise control group to determine the impact of random/measurement error on the variability associated with VO2peak and OBLAWR responses to endurance training. Therefore, the purpose of this study was to determine whether true individual differences exist in responses to training by assessing whether the variability in VO2peak and OBLAWR responses following training exceeded the variability in a non-training control group.
 Methods: 16 recreationally active males completed two incremental ramp tests to determine VO2peak and OBLAWR. Participants were assigned into the control group (n = 7) or the training group (n = 9; endurance training: 30 minutes of 65% of work rate at VO2peak, four times per week) in a manner to counterbalance baseline VO2peak measures.
 Results: VO2peak increased significantly (p < 0.05) (+338 ± 416.2 mL/min/kg) and OBLAWR (+32.1 ± 29.2 W) increased following endurance training. The SD in change scores was greater in the training group for VO2peak and OBLAWR than the parallel control group. Specifically, this resulted in large and moderately-large effect sizes at respective values of 0.6 for VO2peak and 0.5 for OBLAWR.
 Conclusion: Although these preliminary results may suggest that the variability in VO2peak and OBLAWR responses to endurance training reflect true inter-individual variability beyond random/measurement error, a definitive conclusion can be made upon the completion of the study.