Reliability of achieving target dehydration levels using a portable infrared sauna protocol in healthy young adults.

Abstract

<h4>Background</h4>Although environmental chambers have traditionally been used to study passive dehydration and recovery in the context of sports nutrition, portable infrared saunas may provide a more accessible and cost-effective alternative. This study aimed to assess the efficacy and test-retest reliability of achieving target body mass (BM) losses using a portable infrared sauna.<h4>Methods</h4>Fifteen healthy adults (11 males: 22.46 ± 2.70 years, 175.48 ± 6.54 cm, 76.35 ± 9.78 kg; 4 females: 21.00 ± 2.58 years, 163.10 ± 2.79 cm, 54.78 ± 4.25 kg) completed two identical dehydration trials separated by at least 72 hours. After a standardized warm-up, participants alternated for up to 20 minutes of sauna exposure (~66 °C) with 5 minutes of rest (~23 °C) until reaching 2.8% ± 0.3% (males) or 2.4% ± 0.3% (females) BM loss. The dependent variables were total sauna time, maximum core temperature (MCT), average sauna temperature when entering, average sauna temperature when exiting, absolute BM loss, relative BM loss, absolute BM loss per 60 minutes, and relative BM loss per 60 minutes. Reliability was evaluated using a two-way fixed intraclass correlation coefficient (ICC) and coefficients of variation (CVs; acceptable <15%).<h4>Results</h4>The point estimate ICCs ranged from 0.710 to 0.969, with CVs < 5%. There were significant intertrial differences for MCT (Trial 1 > Trial 2, <i>p</i> < 0.05), whereas all other variables demonstrated no significant differences.<h4>Conclusions</h4>These findings indicate that a portable infrared sauna protocol yields reliable dehydration outcomes (CV < 5%; ICC > 0.75) and achieves > 2% BM loss in under 180 minutes, supporting its use when environmental chambers are unavailable.