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

Nutrients. 2021 May 26;13(6):1807. doi: 10.3390/nu13061807.


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 (p > 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 (p < 0.05). There were no significant differences in mean SR between LOW-MOD (p > 0.9), but significant differences between LOW-HIGH and MOD-HIGH (p < 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.

Keywords: fluid balance; fluid loss; hyperhydration; hypohydration; hyponatremia.

MeSH terms

  • Athletes*
  • Bicycling
  • Dehydration*
  • Eating
  • Endurance Training*
  • Exercise
  • Female
  • Humans
  • Male
  • Plant Roots
  • Running
  • Sweat*
  • Temperature