The purpose of this study was to compare daily calcium (Ca) losses in sweat (S) and urine (U) on an exercise day (E) with losses on the preceding day (i.e., a rest day) during which no exercise (NE) was performed. Ten healthy male volunteers (23.9 +/- 3.2 years) performed a single bout of moderate exercise (running at 80% HRmax) for 45 min in a warm (32 degrees C, 58% relative humidity) environment on E. When E and NE were compared, neither Ca intake (1,232 +/- 714 and 1, 148 +/- 482 mg, respectively) nor urinary Ca excretion (206 +/- 128 and 189 +/- 130 mg, respectively) were different (p >.05). Sweat Ca losses during the exercise bout averaged 45 +/- 12 mg. The results indicate that, although a small amount of Ca is lost in sweat during 45 min of moderate-intensity exercise, measured (sweat and urine losses combined) Ca losses (251 +/- 128 and 189 +/- 130 mg) were not different (p >.05) between days (E and NE, respectively). These data suggest that moderate exercise for up to 45 min in a warm, humid environment does not markedly increase Ca intake requirements.
Adult Calcium