A Case-Series Observation of Sweat Rate Variability in Endurance-Trained Athletes

• Main Authors: JohnEric W. Smith, Marissa L. Bello, Ffion G. Price
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Nutrients
• Subjects: hypohydration; hyperhydration; hyponatremia; fluid loss; fluid balance
• Online Access: https://www.mdpi.com/2072-6643/13/6/1807

Adequate fluid replacement during exercise is an important consideration for athletes, however sweat rate (SR) can vary day-to-day. The purpose of this study was to investigate day-to-day variations in SR while performing self-selected exercise sessions to evaluate error in SR estimations in similar temperature conditions. Thirteen endurance-trained athletes completed training sessions in a case-series design 1x/week for a minimum 30 min of running/biking over 24 weeks. Body mass was recorded pre/post-training and corrected for fluid consumption. Data were split into three Wet-Bulb Globe Thermometer (WBGT) conditions: LOW (<10 °C), MOD (10–19.9 °C), HIGH (>20 °C). No significant differences existed in exercise duration, distance, pace, or WBGT for any group (<i>p</i> > 0.07). Significant differences in SR variability occurred for all groups, with average differences of: LOW = 0.15 L/h; MOD = 0.14 L/h; HIGH = 0.16 L/h (<i>p</i> < 0.05). There were no significant differences in mean SR between LOW-MOD (<i>p</i> > 0.9), but significant differences between LOW-HIGH and MOD-HIGH (<i>p</i> < 0.03). The assessment of SR can provide useful data for determining hydration strategies. The significant differences in SR within each temperature range indicates a single assessment may not accurately represent an individual’s typical SR even in similar environmental conditions.