Comparison of Water Turnover Rate between Female Soft Tennis Players and Age-matched Sedentary Individuals during Extensive Summer Training*

Abstract

The objective of this study was to determine the water loss in soft tennis players due to prolonged training in a hot environment. Water turnover (WT) was measured from the elimination rates of deuterium oxide in 8 female collegiate soft tennis players (tennis group; TG) and 6 sedentary age-matched individuals (sedentary group; SG). The TG completed, on average, 4 h of training per day during 7 days of WT measurement. The mean ambient temperature during training averaged 31.3°C. The WT of the SG was measured during a 14-day-period when they did not exercise regularly. Mean (standard deviation) of WT in the TG was 5.1 (0.7) L per day, which was almost two times faster than that in the SG [2.5 (0.7) L/day]. Even when expressed relative to body mass or as a percentage of total body water (TBW), WT was still nearly two times faster in the TG [99.2 (15.2) mL/kg and 16.0 (2.0) %TBW] than in the SG [46.9 (14.9) mL/kg and 8.7 (3.0) %TBW]. WT values in the TG were among the highest reported ever. These results suggest that the water demand of soft tennis players during extensive summer training is tremendous, and optimal strategies to maintain hydration are required.