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Exercise alone or in combination with environmental heat stress can elevate blood S-100 beta protein concentrations. However, the explanatory power of exercise with marked environmental heat stress on the appearance of S-100 beta is questionable. It is possible that the process of heat acclimation might afford additional insight. Purpose: Determine the S-100 beta response to moderate intensity exercise with heat strain before and after heat acclimation. Methods: Nine healthy male volunteers completed 10 consecutive days of heat acclimation consisting of up to 100 minutes of treadmill walking 91.56 m/s, 4% grade) in the heat (45 deg C, 20% relative humidity). Changes in heart rate (HR), rectal temperature (Tre), and sweat rate (SR) were examined to determine successful acclimation. Area under the curve (AUC) for Tre > 38.5 deg C was calculated to assess cumulative hyperthermia. Blood samples were taken before and after exercise on days 1 and 10 and analyzed for serum osmolality and S-100 beta concentration. Results: All subjects displayed physiological adaptations to heat acclimation, including a significant (P< 0.05) reduction in final HR (161 to 145 b/mm) and Tre (39.0 to 38.4 C), as well as a modest (approx. 10%) increase in SR (1.10 to 1.20 L/hr; p=0.09). No differences were observed in pre-to-post exercise serum S-100 beta concentrations on day 1 or day 10, nor were differences observed in S-100 beta values between days 1 and 10. No significant correlations were found between S-100 beta values and any variable of interest. Conclusions: S-100 beta concentrations do not necessarily increase in response to exercise heat strain and no effect of heat acclimation on S-100 beta could be observed despite other quantifiable physiological adaptations., Published in Medicine & Science in Sports & Exercise, v p1477-1482, 2008.

This study determined whether a torso-vest forced ambient air body ventilation system (BVS) reduced physiological strain during exercise-heat stress. Seven heat-acclimated volunteers attempted nine, 2-h treadmill walks at 200 W/sq m in three environments, -40 C, 20% rh (HD), 35 C, 75% rh (HW), and 30 C, 50% rh, (WW) wearing the Army Combat Uniform, interceptor body armor (IBA) and Kevlar helmet. Three trials in each environment were BVS turned on (BVS (On)), BVS turned off (BVS(Off)), and no BVS (IBA). In HD, BVS(On) significantly lowered core temperature (T(ak)), mean torso skin temperature (T(torso)), thermal sensation (TS), heat storage (S), and physiological strain index (PSI), versus BVS(off) and IBA (P < 0.05). For HW (n = 6), analyses were possible only through 60 min. Exercise tolerance time (min) during HW was significantly longer for BVS(On) (116 +/- 10 min) versus BVS(off) (95 +/- 22 min) and IBA (96 +/- 18 min) (P < 0.05). During HW, BVS(On) lowered HR at 60 min versus IBA T(sk) from 30 to 60 min. versus BVS(Off) and IBA, and PSI from 45 to 60 min versus BVS(Off) and at 60 min versus IBA (P < 0.05). BVS(On) changes in T(re) and HR were lower in HD and HW. During WW, BVS(On) significantly lowered HR, T( sk) and T(torso) versus BVS(Off) and IBA (P < 0.05) during late exercise. Sweating rates were significantly lower for BVS(On) versus BVS(Off) and IBA in both HD and WW (P < 0.05), but not HW. These results indicate that BVS(On) reduces physiological strain in all three environments by a similar amount; however, in hot-dry conditions the BVS(Off) increases physiological strain., Published in European Journal of Applied Physiology, v103 p307-314, 2008.

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., Pub. in Medicine & Science in Sports & Exercise, v40 n5 p886-891, 2008.

Copper, iron and zinc are nutritionally essential trace minerals that confer vital biological roles including the maintenance of cell structure and integrity, regulation of metabolism, immune function, oxygen transport, and muscle and central nervous system function. Dietary Reference Intakes (DRIs) for these minerals are useful for the general population, but these guidelines may be inadequate for some populations (e.g., soldiers, athletes) who experience copious sweating due to high physical activity levels and/or frequent exposure to extreme environmental conditions. The trace mineral content of sweat may predispose these populations to subclinical/clinical nutritional deficiencies. Studies on sweat trace mineral losses report highly variable results. Much of the variability may be methodological. Non-standardization of collection techniques, collections sites (local versus whole body), and numerous other variables cloud definitive conclusions on sweat trace mineral losses. The objectives of this manuscript are to 1) review the literature on swear copper, iron and zinc losses, 2) present the potential sources of variability, 3) interpret findings in relation to nutritional needs, and 4) identify directions for future research., Published in Current Nutrition & Food Science, v3 p236-241, 2007.