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

## TL;DR

Home-based heat training improves fitness and performance in hot conditions for women, and maintaining the training further boosts performance.

## Contribution

This study shows that heat maintenance training enhances the benefits of initial heat acclimation in females.

## Key findings

- Heat maintenance training improves performance in both temperate and hot conditions.
- Home-based heat acclimation increases peak power output and reduces time trial times.
- Heat maintenance does not increase hemoglobin mass after initial acclimation.

## 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), V˙O2max, 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, T¯
sk), heart rate, peak cardiac output (Q˙peak), 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. V˙O2max, Tre, T¯
sk, heart rate, and Q˙peak 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.

At‐home heat acclimation improves thermoneutral fitness and exercise performance in a hot environment in females. Heat maintenance further potentiates performance.