The influence of hot humid and hot dry environments on intermittent-sprint exercise performance

PURPOSE: This study examined the effect of a hot humid (HH) compared to a hot dry (HD) environment, matched for heat stress, on intermittent sprint performance. In comparison to HD, HH environments compromise evaporative heat loss and decrease exercise tolerance.6 It was hypothesized HH would produce greater physiological strain and reduce intermittent sprint exercise performance compared to HD. METHOD: Eleven male team sports players completed the cycling intermittent sprint protocol (CISP) in three conditions, temperate (TEMP; 21.2 ±1.3°C, 48.6 ± 8.4% relative humidity (rh)), HH (33.7 ± 0.5°C, 78.2 ± 2.3% rh) and HD (40.2 ± 0.2°C, 33.1 ± 4.9% rh), with both heat conditions matched for heat stress. RESULTS: All participants completed the CISP in TEMP but three failed to completed the full protocol of twenty sprints in HH and HD. Peak power output (PPO) declined in all conditions (P < 0.05), but was not different between any condition (sprints 1 - 14 (n = 11); HH, 1073 ± 150 W; HD, 1104 ± 127 W; TEMP, 1074 ± 134; sprints 15 - 20 (n = 8); HH, 954 ± 114 W; HD, 997 ± 115 W; TEMP, 993 ± 94; P > 0.05). Physiological strain (PSI) was not significantly different in HH compared to HD but HH was higher than TEMP (P < 0.05). CONCLUSION: Intermittent sprint exercise performance of 40 minutes duration is impaired, but not different in hot humid and hot dry environments matched for heat stress despite evidence of a trend towards greater physiological strain in a hot humid environment