Effect of heat acclimation on sweat minerals.
OBJECTIVE
This study examined the impact of 10 d 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 degrees C on 10 consecutive days in an environmental chamber set at 45 degrees 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 +/- 7.22 mM) was significantly lower than day 1 (54.49 +/- 16.18 mM) (P < 0.05). Sweat mineral concentrations of calcium (approximately 29%), copper (approximately 50%), and magnesium (approximately 43%) were also significantly lower on day 10 versus day 1 of heat acclimation (P < 0.05). A trend for lower sweat iron (approximately 75%; P = 0.07) and zinc (approximately 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 (approximately 27%), copper (approximately 46%), and magnesium (approximately 42%) (P < 0.05), but not iron (75%) or zinc (approximately 16%) (P > 0.05), from day 1 to day 10.


CONCLUSIONS
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.
Chinevere
Troy D
TD
U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. Troy.Chinevere@us.army.mil
Kenefick
Robert W
RW
Cheuvront
Samuel N
SN
Lukaski
Henry C
HC
Sawka
Michael N
MN
D000328:Adult; D002118:Calcium / Q000032:analysis; D003300:Copper / Q000032:analysis; D018882:Heat Stress Disorders / Q000378:metabolism*; D006358:Hot Temperature; D006801:Humans; D007501:Iron / Q000032:analysis; D008274:Magnesium / Q000032:analysis; D008297:Male; D013542:Sweat / Q000737:chemistry*; D013546:Sweating; D015032:Zinc / Q000032:analysis
D003300:Copper; D007501:Iron; D008274:Magnesium; D015032:Zinc; D002118:Calcium