Abstract
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.
Highlights
The lean tissue of the human body is composed of approximately 73% water [1].Variations in body fat will result in individual body water levels ranging from ~50–70%of total body mass
There were no significant differences in duration, distance, pace, and Wet-Bulb Globe Thermometer (WBGT) for any of the groups (p > 0.07)
LOW WBGTs demonstrated an average difference of 0.15 L/h in sweat rate between highest and lowest recordings (p < 0.01)
Summary
The lean tissue of the human body is composed of approximately 73% water [1].Variations in body fat will result in individual body water levels ranging from ~50–70%of total body mass. As a result of hypohydration there is increased cardiovascular strain [7], thermal strain [8], perceived exertion [9], and reduced oxygen and nutrient delivery to the exercising muscle [8,10,11]. Due to these physiological responses to reductions in body water, exercise performance has been shown to be diminished with as little as 2% hypohydration [12,13,14,15,16,17,18]
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