The relationship between water intake, hydration biomarkers and physical activity of young male athletes in Beijing, China: A cross-sectional study.

Background and objectives: To explore the relationship between water intake, hydration biomarkers and physical activity of young male athletes.

Methods and study design: A 7-day cross-sectional study was conducted among 45 male athletes aged 18-25 years in Beijing, China. Total drinking fluids (TDF) was obtained using 7-day 24-h fluid intake questionnaire. Water from food (WFF) was assessed using the methods of food weighing, duplicate portion method and laboratory analysis. Physical activity was evaluated using physical activity energy expenditure (PAEE) and metabolic equivalent of task (MET).

Results: Totally, 42 participants completed the study. The medians of total water intake (TWI), TDF and WFF of participants were 2771 mL, 1653 mL and 1088 mL respectively. Jonckheere-Terpstra test showed a significant increase trend toward higher TWI and TDF with higher PAEE level (Z=2.414, p=0.016; Z=2.425, p=0.015). Spearman's rank correlation showed that TWI was positively correlated with PAEE (rs=0.397, p=0.009). TDF showed a positive correlation with PAEE and MET (rs=0.392, p=0.010; rs=0.315, p=0.042). The median urine volume was 840 mL, urine specific gravity was 1.020, and 24-h urine osmolality was 809 mOsm/kg. Significant differences were found in plasma cortisol among the four MET groups (χ2=8.180; p=0.042).

Conclusions: Young male athletes with higher physical activity level had higher amounts of TWI and TDF than their counterparts but had similar hydration biomarkers. There was a high incidence of dehydration in athletes, and attentions need to be paid on the intake of TDF among them to maintain the optimal hydration status.