(42) EFFICACY AND RELIABILITY OF PORTABLE INFRARED SAUNA USE AS A DEHYDRATION INTERVENTION MODALITY

Purpose: Physical labor and sport settings are often associated with demanding tasks and heat exposure, increasing the risk of significant fluid loss and heat related injuries. While environmental chambers are traditionally used for studying dehydration, portable infrared saunas offer a more accessible and cost-effective alternative. However, limited data exists on the efficacy and reliability of sweat rates and body mass (BM) losses when using them. Therefore, the purpose was to assess efficacy and the test-retest reliability of sweat rates and body mass losses using a portable infrared sauna. Methods: Fifteen healthy participants (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) who self-reported a moderate to heavy sweat rate completed two identical dehydration trials at least 72 hours apart. Participants arrived at both trials well hydrated, confirmed via urine specific gravity ( < 1.02). Participants were weighed wearing light athletic clothing and completed a 15-minute treadmill warm-up (5 km/hour; 3% grade). The intervention involved alternating exposures of 20 minutes in the sauna set at the maximum temperature of ~66°C and 5 minutes of passive rest in a thermoneutral environment (~23°C). Participants were weighed during each 5-minute rest period until they achieved a BM loss of 2.8±0.3% for males or 2.4±0.3% for females. Participants wore an algorithmic-based thermal sensor that estimated core temperature and sauna temperature was monitored via wireless weather station. Dependent variables include total sauna time (TT), maximum core temperature (MCT), absolute BM loss (ABM_DIFF), relative BM loss (%BM_DIFF), absolute BM loss per 60 minutes (ABM_SLOPE), relative BM loss per 60 minutes (%BM_SLOPE), average sauna temperature when entering (ST_IN), and average sauna temperature when exiting (ST_OUT). Test-retest reliability was assessed with a two-way fixed intraclass correlation coefficient (ICC) analysis. Dependent samples t-tests were used to assess potential differences between exposure trials. Results: Data are presented in Table 1. Moderate reliability (ICC=0.50-0.75) was observed for ST_IN and ST_OUT. Good reliability (ICC=0.75-0.90) was observed for TT, MCT, %BM_DIFF, ABM_SLOPE, and %BM_SLOPE. Excellent reliability (ICC >0.90) was observed for ABM_DIFF and ABM_SLOPE. Significant differences were observed for MCT (Trial 1 >Trial 2, p< 0.05), whereas all other variables demonstrated no significant differences between each intervention. Conclusions: Using a portable infrared sauna as a dehydration intervention modality provides reliable outcomes related to time, temperature, sweat rate, and BM loss. Additionally, participants consistently achieved their intended dehydration levels. Practical Applications: Portable infrared saunas provide individuals with an inexpensive and accessible modality for those who intend to conduct research involving passive dehydration via heat exposure as an intervention. Acknowledgements: This project was funded by Abbott Nutrition.