Comparison of body water turnover in endurance runners and age-matched sedentary men

This study compared the body water turnover in endurance athletes and age-matched sedentary men. Eight competitive endurance athletes (20.8+/-1.9 yr) and age-matched eight sedentary men (21.6+/-2.5 yr) participated in this study. Total body water and body water turnover were measured using the deuterium (D(2)O) dilution technique. Urine samples were obtained every day for 10 days after oral administration of D(2)O. The day-by-day concentrations were used to calculate the biological half-life of D(2)O and body water turnover. Maximal oxygen uptake (VO(2max)) and oxygen uptake corresponding to ventilatory threshold (VO(2VT)) as an index of aerobic capacity were determined during a graded exercise test. Both VO(2max) and VO(2VT) were higher in the exercise group than in the sedentary group (P<0.05). The biological half-life of D(2)O was significantly shorter in the exercise group than in the sedentary group (5.89+/-0.81 days vs. 7.52+/-0.77 days, P<0.05), and the percentage of the body water turnover was significantly higher in the exercise group than in the sedentary group (11.99+/-1.96% vs. 9.39+/-1.21%, P<0.05). The body water turnover was correlated with VO(2max) and VO(2VT), respectively (P<0.05). Based on these findings, this study speculates that a level of physical activity may induce a body water turnover higher in the healthy state, since the better trained subjects have a higher body water turnover.