International Journal of Exercise Science 10(5): 721-733, 2017. Hot yoga participants are at risk for dehydration due to the nature of the environment they exercise in. Therefore, the purpose of this study was to investigate the pre-exercise hydration status, fluid balance, perception of sweat loss, and sweat sodium loss in 21 male and female hot yoga participants (mean age ± SD, 33.0 ± 10.5 yr; mass, 70.7 ± 11.0 kg). Data was recorded pre and post a one- hour hot yoga class (38.7 ± 2.6 °C, 36 ± 13% relative humidity). Pre-exercise urine specific gravity (USG), hydration status, body mass changes, and fluid intake were recorded and sweat rate was calculated. Sweat sodium concentration was examined using sweat patches, and each participant reported their perception of sweat loss. A paired t test was used to identify significance between measured and perceived sweat loss and Pearson’s correlation analyses were used to assess relationships between variables. Seventy six percent of participants began hot yoga euhydrated (USG < 1.020). Sweat rate was 0.9 ± 0.6 L·h-1. Despite free access to fluids during class, consumption was low (0.2 ± 0.2 L·h-1) and 33% did not consume any fluids. Consequently, mean percent body mass loss was 0.9 ± 0.6% and about half of the participants lost at least 1% of body mass. Participants underestimated perception of sweat loss (p = 0.01). Mean sweat sodium concentration was 49.1 ± 19.2 mmol·L-1. Findings from this study highlight the individual variability that occurs in hydration management in yoga participants and the need for personalized hydration guidelines.

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