Effect of Heat Acclimation on Sweat Minerals
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA THERMAL AND MOUNTAIN MEDICINE DIVISION
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Purpose This study examined the impact of 10 days of exercise-heat acclimation on sweat mineral concentrations. Methods Eight male subjects walked on a treadmill at 3.5 mph, 4 grade for 100 continuous minutes or until rectal temperature reached 39.5 C on 10 consecutive days in an environmental chamber set at 45 C, 20 relative humidity. Arm sweat samples were collected during the first 30 min of exercise-heat stress on days 1 and 10 using a polyethylene arm glove. Results Final core temperature and HR values were significantly lower P 0.05 on day 10 versus day 1. Whole-body sweating rates increased by approximately 6 P 0.12. Sweat sodium concentration on day 10 36.22 or - 7.22 mM was significantly lower than day 1 54.49 or - 16.18 mM P 0.05. Sweat mineral concentrations of calcium 29, copper 50, and magnesium 43 were also significantly lower on day 10 versus day 1 of heat acclimation P 0.05. A trend for lower sweat iron 75 P 0.07 and zinc 23 P 0.10 concentrations were observed from day 1 to day 10. The estimated hourly sweat mineral losses arm concentration x whole-body sweat rate were reduced for calcium 27, copper 46, and magnesium 42 P 0.05, but not iron 75 or zinc 16 P 0.05, from day 1 to day 10. Conclusion Exercise-heat acclimation conserves arm sweat mineral concentrations and possibly whole-body sweat losses of calcium, copper, and magnesium, and may reduce sweat iron and zinc concentrations.
- Stress Physiology