Sweat rates during international open water competitions and the importance of feedings in elite swimmers

Open water swimming is an outdoor discipline with different environmental characteristics that affects athletes’ performance. The aim of this work was to understand how hydration affects the sweat rate during a 5 and 10 km event in elite swimmers. A total of 45 elite swimmers (22 females and 23 males) were analysed during an international event over 5 km or 10 km in different water temperature conditions. Sweat rate (L·h−1), percentage of weight loss and drink ingestion (L) were measured. An ANOVA test was used to indicate the significance of the difference. The results showed that warm water on 10 k sweat rate is statistically significant (p < 0.001) (-1.99 ± 0.34 vs -1.14 ± 0.36 vs -1.48 ± 0.49 L·h−1), and in cold water with wetsuit, weight loss (p < 0.05) and drink ingestion (p < 0.001) are significant too (-2.27 ± 0.75 %; 1.31 ± 0.63 L). The results show a higher sweat rate in warm water and weight loss with wetsuit, drink ingestion is lower in cold water. This study confirms that it is important to analyse the environmental characteristics of an open water swimming competition to plan a specific hydration protocol to get the best performance.