Sweat Rate, Fluid Consumption, and Hydration Indices for Youth Soccer Players

Abstract

PURPOSE: Previous research has shown that youth participating in sports camps begin hypohydrated and display inadequate hydration during camp. The purposes of this study were to measure sweat rate (SR), fluid consumption (FC), and various hydration indices and to use this information as tools to educate youth soccer players about hydration status. METHODS: Thirty-three boys and 17 girls (50.2±9.4 kg, 159.1±7.2 cm, 13±0.9 yrs, and 8±2 yrs soccer experience) volunteered to participate as part of a summer soccer camp in which they practiced 2–3 times per day for 5 consecutive days. Subjects were randomly assigned to non-intervention (NI) or educational intervention (EI) and grouped as younger (10–13 yrs) or older (14–17 yrs) at camp registration. EI took place in the evening on days 2–4 and lasted for approx. 5 min in groups of 2–3. SR, FC during practice, and various hydration indices were used as educational tools. SR was calculated from body weight (BW) taken immediately before practice and immediately post practice, while correcting for FC. Urine sample and BW were obtained before breakfast (AM) and before dinner (PM) each day. RESULTS: SR (1/hr) was greater in males vs females (1.01±0.31 vs 0.69±0.21, respectively) and older vs younger (1.10±0.31 vs 0.77±0.25, respectively). Older males and females had sweat rates of 1.17±0.23 and 0.69±0.56 l/hr, respectively. Younger males and females had sweat rates of 0.84±0.30 and 0.68±0.15 l/hr, respectively. FC (l/hr) during practice was greater for males than females (0.81 vs 0.69, p=0.015), and no differences existed between older and younger (0.91 vs 0.64, p=0.185). A higher rate of FC did not compensate for increased SR in males compared to females, so they became more dehydrated during practice (−0.56 vs 0.06 %BW loss, respectively). Of the 60.4% that lost weight during practice, 30.9% lost >1% BW. EI had no effect on SR or FC (p>.05). Average urine specific gravity (USG) was lower in EI than NI for males (p=0.007) and younger (p=0.045). USG changes from AM to PM increased as the week progressed (p=0.019), but EI failed to reverse this trend (p>.05). Changes in urine osmolality from PM to AM of the next day showed tendencies for EI subjects to have improved rehydration compared to NI (−39 vs +42 mOsm/kg·H2O, respectively). CONCLUSIONS: FC and SR, although rarely measured in the field, were similar to published lab findings. Although FC closely matched SR for all groups, the subjects remained chronically dehydrated during camp. EI may influence the hydration status of males and females and younger and older soccer players. Future studies with EI need to further emphasize hydration when not exercising.