The Influence of Heat Acclimation and Hypohydration on Post-Weight-Loss Exercise Performance

The purpose of this study was to investigate if heat acclimation would improve exercise performance in athletes recovering from acute hypohydration and if restricting fluid ingestion during acclimation sessions would amplify the observed changes.

At a glance:

• Heat acclimation may be a viable strategy for improving athlete performance in weight-restricted sports
• Three hours of ad libitum food and fluid ingestion is insufficient to recover from acute hypohydration
• Future research should examine the mechanisms by which acute hypohydration influences exercise performance

Full reference and abstract:

Barley, O. R., Chapman, D. W., Mavropalias, G. & Abbiss, C. R. (2019). The influence of heat acclimation and hypohydration on post-weight-loss exercise performance. International Journal of Sports Physiology and Performance. 1-26. Epub ahead of print.

Purpose: This study examined the influence of: i) fluid intake on heat acclimation and ii) the subsequent effects on exercise performance following acute hypohydration.

Methods: Participants were randomly assigned to one of two groups, either able to consume water ad libitum (n = 10; age 23 ± 3 y; height 1.81 ± 0.09 m; body mass 87 ± 13 kg; HAW) or not allowed fluid (n = 10; age 26 ± 5 y; height 1.76 ± 0.05 m; body mass 79 ± 10 kg; HANW) throughout 12 x 1.5 h passive heat acclimation sessions. Experimental trials were completed on two occasions prior (two baseline trials) and one following the heat acclimation sessions. These sessions involved 3 h of passive heating (45°C, 38% relative humidity) to induce hypohydration followed by 3 h of ad libitum food and fluid intake after which participants performed a repeat sled-push test to assess physical performance. Urine and blood samples were collected before, immediately and 3 h following hypohydration to assess hydration status. Mood was also assessed at the same time-points.

Results: No meaningful differences in physiological or performance variables were observed between HANW and HAW at any time-point. Using pooled data, mean sprint speed was significantly (P<0.001) faster following heat acclimation (4.6±0.7 s compared to 5.1±0.8 s). Further, heat acclimation appeared to improve mood following hypohydration.

Conclusions: Results suggest passive heat acclimation protocols may be effective at improving short duration repeat-effort performance following acute hypohydration.