Fluid Loss in Recreational Surfers

Purpose: Surfing offers unique challenges to thermoregulation and hydration. The purpose of this study was to quantify fluid loss in recreational surfers, and to analyze the effects of water temperature, air temperature, exercise intensity, duration, and garment thickness on the total amount of fluid lost during a surf session. Methods: 254 male and 52 female recreational surfers were recruited from San Diego, Costa Rica, and Australia to participate in the study. Subjects' hydration status was assessed by comparing nude body mass pre- and post-surf session. Heart rate (HR), used as an index of exercise intensity, was measured throughout the session. Environmental conditions and surf characteristics were recorded. Results: The difference between average pre-weight (73.11±11.88 kg) and average post-weight (72.51±11.78) was statistically significant (0.60±0.55, p0.001). On average, surfers lost 0.82±0.73% body weight. In multivariable linear regression, water temperature, session duration, and BMI were all associated with fluid loss. For every 5 degree increase in water temperature, there was a 0.23 kg (SE=0.014; p0.001) increase in fluid loss, for every 10-minute increase in session duration, there was a 0.06 kg (SE=0.001; p0.001) increase in fluid loss, and for every 2 unit increase in BMI, fluid loss increased by 0.05 kg (SE=0.03; p-value=0.02). The regression model accounted for 26% (r2=0.26) of the variability in fluid loss among surfers. Conclusion: The findings of this study suggest that prolonged surfing at high environmental temperatures in subjects with high BMI's can result in significant body water deficits. Since there is no opportunity to rehydrate during the sport, surfers must properly hydrate before surfing to avoid the detrimental effects of dehydration.