Effects of Heat Acclimation on Heat-Exercise Tolerance in Untrained and Endurance-Trained Men Wearing NBC Protective Clothing
Abstract
Responses were compared between nine untrained (UT) men and six men who had participated in 8 weeks of endurance training (ET). Both groups underwent 6 days of heat acclimation in a climatic chamber that was maintained at 40 +/- 0.5 deg C and 30 +/- 1% rh. Subjects were tested before and after acclimation wearing either standard military combat clothing or nuclear, biological and/or chemical (NBC) protective clothing. Test sessions involved treadmill walking at 4. 8 km - h(-1) and 2% grade f or a maximum of 120 min. In UT subjects, heat acclimation increased plasma volume (+8 +/2%), but VO sub 2max and heat-exercise tolerance time were unchanged. When wearing standard combat clothing, acclimation decreased average values of heart rate, rectal temperature (T sub re), mean skin temperature (T sub sk), thermal discomfort, and metabolic heat production. When wearing NBC protective clothing, the only significant change was in T sub re. Acclimation induced an increase of sweat secretion but no statistically significant increase of sweat evaporation in NBC protective clothing. In ET subjects, acclimation reduced thermal discomfort when wearing standard combat clothing, and T sub re and T sub sk when wearing NBC protective clothing. The results suggest that heat acclimation did little to improve exercise tolerance when wearing NBC protective clothing in hot environments, although it reduced thermoregulatory strain by lowering mean body temperature, irrespective of training status. Sweat production, Seat evaporation, Rectal temperature, Skin temperature, Heart rate, Blood volume, Discomfort, Metabolic rate, Prolonged work.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1993
- Accession Number
- ADA277522
Entities
People
- Roy J. Shephard
- Tom M. Mclellan
- Yukitoshi Aoyagi
Organizations
- DRDC Toronto