Abstract des Autors

Total body water (TBW) and water turnover rates (WTR) of six competitive male cyclists (CG) and six age-matched sedentary men (SG) were determined using deuterium oxide dilution and elimination. During the 7 day study, individuals in the CG cycled daily outside on average 50 (range 12-146) km at an average speed of 29 km/h, while the SG did no regular exercise. Dur-ing the study, the weather was cool (10 [4-18]degrees C), mainly cloudy but dry. Daily average (median [range]) nude body mass remained essentially the same in the CG (77.25 [76.54-77.54] kg) and SG (65.04 [64.45-65.44] kg). Expressed as a percentage of body mass, median TBW of the CG (70.1 [65.5-73.9]%) was greater than that of the SG (63.5 [52.7-71.0]% ). Aver-age median WTR was faster in the CG (47 [42-58] ml x kg/d) than the SG (36 [29-50] ml x kg/d). The average median daily urinary loss was similar in the CG (27 [22-33]ml x kg/d) and SG (29 [24-31]ml x kg/d). Calculated non-renal daily water loss was faster in the CG (19 [13-35] ml x kg/d) than the SG (6 [5-22] ml x kg/d), but there was no relationship between the aver-age distance cycled daily and the WTR. This study demonstrates that WTR are faster in indi-viduals undertaking prolonged exercise than in sedentary men, and that the difference was due to the almost three times greater non-renal water losses that the exercising group incurred. This suggests that exercise-induced increases in respiratory water loss and sweat rate are major factors in water loss even in cool environments. Verf.-Referat