Three weeks of heat maintenance potentiates the benefits of heat acclimation in trained females

Abstract

We investigated whether heat adaptation (HA) could be maintained in trained females following an initial acclimation period. The experimental group (EXP, n = 11) completed 10 sessions of HA over 2 weeks, followed by nine sessions of HA maintenance (HAM) over 3 weeks. HA was induced with home-based stationary cycling while overdressing. A control group (CON, n = 4) was exposed to heart rate-matched thermoneutral training. Prior to and at the end of the acclimation period (PRE, MID) and following the maintenance period (POST), (Formula presented.), peak power output (PPO), and hemoglobin mass (Hbmass) were determined in 18°C, before a 20 km time trial (TT) in 35°C, 45% RH. During the TT, rectal and mean skin temperature (Tre, (Formula presented.) sk), heart rate, peak cardiac output ((Formula presented.)), and sweat rate were measured. PPO increased (p = 0.0003) and TT times decreased (p < 0.0001) from PRE to MID and POST in EXP but not CON. (Formula presented.), Tre, (Formula presented.) sk, heart rate, and (Formula presented.) remained stable in both groups. Sweat rate only increased in EXP from PRE to POST (p = 0.0197). Hbmass did not change in EXP. HAM potentiated hot exercise performance compared to HA, as demonstrated by improvements in both temperate and hot conditions. While HAM suffices to further develop thermal resistance, it is unsuitable to increase Hbmass following 10 days of HA or 3 weeks of HAM. Our findings demonstrate that females can achieve HA by overdressing at home for 10 days and that HAM provides further benefits.