The time-course of adaptations in thermoneutral maximal oxygen consumption following heat acclimation

Purpose: This study investigated the effects of a 10-day heat acclimation (HA) programme on the time-course of changes in thermoneutral maximal oxygen uptake (V ̇O2max) during and up to 10 days post-HA. Methods: Twenty-two male cyclists were assigned to a HA or control (Con) training group following baseline ramp tests of thermoneutral V ̇O2max. Ten days of fixed-intensity (50% baseline V ̇O2max) indoor cycling was performed in either ~ 38.0 °C (HA) or ~ 20 °C (Con). V ̇O2max was re-tested on HA days 5, 10 and post-HA days 1, 2, 3, 4, 5 and 10. Results: V ̇O2max initially declined across time in both groups during training (P < 0.05), before increasing in the post-HA period in both groups (P < 0.05). However, V ̇O2max was higher than control by post-HA day 4 in the HA group (P = 0.046). Conclusions: The non-linear time-course of V ̇O2max adaptation suggests that post-testing should be performed 96-h post training to identify the maximal change for most individuals. In preparation for training or testing, athletes can augment their aerobic power in thermoneutral environments by performing 10 days HA but the full effects will manifest at varying stages of the post-HA period.