The effect of medium-term heat acclimation on endurance performance in a temperate environment

We investigated whether an 11-day heat acclimation programme (HA) enhanced endurance performance in a temperate environment, and the mechanisms underpinning any ergogenic effect. Twenty-four males (V̇O2max: 56.7±7.5 mL∙kg-1∙min-1) completed either: i) HA consisting of 11 consecutive daily exercise sessions (60-90 minutes·day-1; n=16) in a hot environment (40°C, 50% RH) or; ii) duration and exertion matched exercise in cool conditions (CON; n=8 [11°C, 60% RH]). Before and after each programme power at lactate threshold, mechanical efficiency, VO2max, peak power output (PPO) and work done during a 30-minute cycle trial (T30) were determined under temperate conditions (22°C, 50% RH). HA reduced resting (-0.34±0.30°C) and exercising (-0.43±0.30°C) rectal temperature, and increased whole-body sweating (+0.37±0.31 L·hr-1) (all P≤0.001), with no change in CON. Plasma volume increased in HA (10.1±7.2%, P