WATER TURNOVER RATES IN SEDENTARY AND EXERCISING MIDDLE-AGED MEN

Objective-To assess the effect of exercise on water turnover in endura nce trained middle aged men. Methods-Water turnover was assessed using (H2O)-H-2 as a tracer for water in six exercising and six sedentary m iddle aged men over seven consecutive days. The exercising subjects ra n on average 14.8 km per day, while the sedentary group did not take p art in any regular physical activity. Results-The average median (rang e) rate of water turnover (ml . d(-1)) was higher in the exercising gr oup [4673 (4320 to 9606)] than in the sedentary group [3256 (2055 to 4 185); P=0.001]. Although there was a tendency for non-renal water loss es (ml . d(-1)) to be greater in the exercising group [1746 (1241 to 5 196)] than in the sedentary group [1223 (1021 to 1950); P=0.08], the m ajor difference in water loss between the groups was the greater urine output (ml . d(-1)) in those who exercised [3021 (2484 to 4225)] comp ared to those who were sedentary [(1883 (925 to 2266); P = 0.001]. Con clusions-The results suggest that fluid intake in middle aged men who exercise regularly must be greater than that of sedentary individuals of the same age group, and that the difference in volume is in excess of that required to replace exercise induced sweat and respiratory wat er losses.