Effects of 5-Day Heat Acclimation on Workers Wearing Personal Protective Clothing
Main Article Content
Keywords
Heat stress test, Occupational hazards, Hyperthermia
Abstract
Abstract
Introduction: Elevated ambient temperature and personal protective clothing (PPC) induce physiological strain which may be counteracted by heat acclimation. The purpose of this study was to determine if 5-day heat acclimation training (HAT) improves thermal and perceptual responses while wearing chemical, biological, radiological, and nuclear (CBRN) PPC.
Methods: Nine healthy men completed a heat stress test (walking for one hour with CBRN PPC) in 35°C and 50% relative humidity (RH) before and after 5-day HAT. The HAT consisted of five consecutive days of two 45-minute cycling sessions (50% VO2max) wearing athletic clothing separated by a 15 min rest in 45°C and 20% RH. Results of the pre- and post- HAT heat stress tests were compared.
Results: Heat acclimation was seen through 5-day HAT; however, thermoregulatory responses did not improve while wearing CBRN PPC. Improvement (p<0.05, day 1 vs. day 5 HAT) in skin temperature (38.0±0.5°C vs. 37.6±0.5°C), body temperature (38.6±0.4°C vs. 38.3±0.4°C), sweat rate (2.26±0.3kg vs. 2.64±0.3kg), RPE (15.8±2.4 vs. 13.9±3.1), and heat perception (5.7±0.6 vs. 4.9±1.0) were noted. However, no physiological or perceptual improvements (p>0.05) were found in the post-HAT heat stress test.
Conclusions: Heat acclimation adaptations may be blunted by CBRN PPC, thus requiring differing or extended HAT.
References
2. Gonzalez R, McLellan T, Withey W, Chang SK, Pandolf K. Heat strain models applicable for protective clothing systems: comparison of core temperature response. J Appl Physiol 1997;83(3):1017-1032.
3. Henane R, Bittel J, Viret R, Morino S. Thermal strain resulting from protective clothing of an armored vehicle crew in warm conditions. Aviat Space Environ Med. 1979;50(6):599-603.
4. Gill N, Sleivert G. Effect of daily versus intermittent exposure on heat acclimation. Aviat Space Environ Med. 2001;72(4):385-390.
5. Garrett AT, Goosens NG, Rehrer NG, Patterson MJ, Cotter JD. Induction and decay of short-term heat acclimation. Eur J Appl Physiol Occup Physiol. 2009;107(6):659-670.
6. Garrett AT, Creasy R, Rehrer NJ, Patterson MJ, Cotter JD. Effectiveness of short-term heat acclimation for highly trained athletes. Eur J Appl Physiol Occup Physiol. 2012;112(5):1827-1837.
7. Lorenzo S, Halliwill JR, Sawka MN, Minson CT. Heat acclimation improves exercise performance. J Appl Physiol. 2010;109(4):1140- 1147.
8. Pandolf K. Time course of heat acclimation and its decay. Int J Sports Med. 1998;19:S157-160.
9. Aoyagi Y, McLellan TM, Shephard RJ. Interactions of physical training and heat acclimation. Sports Med. 1997;23(3):173-210.
10. Weller AS, Linnane DM, Jonkman AG, Daanen HA. Quantification of the decay and re-induction of heat acclimation in dry-heat following 12 and 26 days without exposure to heat stress. Eur J Appl Physiol Occup Physiol. 2007;102(1):57-66.
11. Parsons K. Human thermal environments: the effects of hot, moderate, and cold environments on human health, comfort, and performance. Crc Press; 2014.
12. Holmer I. Protective clothing in hot environments. Ind Health. 2006;44(3):404-413.
13. McLellan TM. Sex-related differences in thermoregulatory responses while wearing protective clothing. Eur J Appl Physiol Occup Physiol. 1998;78(1):28-37.
14. Montain SJ, Sawka MN, Cadarette BS, Quigley MD, McKay JM. Physiological tolerance to uncompensable heat stress: effects of exercise intensity, protective clothing, and climate. J Appl Physiol 1994;77(1):216-222.
15. Aoyagi Y, McLellan TM, Shephard RJ. Effects of training and acclimation on heat tolerance in exercising men wearing protective clothing. Eur J Appl Physiol Occup Physiol. 1994;68(3):234-245.
16. Chang SK, Gonzalez RR. Benefit of heat acclimation is limited by the evaporative potential when wearing chemical protective clothing. Ergonomics. 1999;42(8):1038-1050.
17. Cheung SS, McLellan TM. Heat acclimation, aerobic fitness, and hydration effects on tolerance during uncompensable heat stress. J Appl Physiol (1985). 1998;84(5):1731-1739.
18. Ramanathan NL. A New Weighting System for Mean Surface Temperature of the Human Body. J Appl Physiol. 1964;19:531-533.
19. Burton AC. Human Calorimetry II. The Average Temperature of the Tissues of the BodyThree Figures. The Journal of Nutrition. 1935;9(3):261-280.
20. Borg GA. Psychophysical bases of perceived exertion. Med sci sports exerc. 1982;14(5):377-381.
21. Loveday DL, Parsons KC, Taki AH, Hodder SG. Designing for thermal comfort in combined chilled ceiling/displacement ventilation environments/Discussion. ASHRAE transactions. 1998;104:901.
22. Aoyagi Y, McLellan TM, Shephard RJ. Effects of endurance training and heat acclimation on psychological strain in exercising men wearing protective clothing. Ergonomics. 1998;41(3):328-357.
23. Neal R, Corbett J, Massey H, Tipton M. Effect of short-term heat acclimation with permissive dehydration on thermoregulation and temperate exercise performance. Scand J Med Sci Sports. 2015.
24. Buono MJ, Heaney JH, Canine KM. Acclimation to humid heat lowers resting core temperature. Am J Physiol. 1998;274(5):R1295-R1299.
25. Yamazaki F. Effectiveness of exercise-heat acclimation for preventing heat illness in the workplace. J UOEH. 2013;35(3):183-192.
26. Greenleaf J, Brock P, Sciaraffa D, Polese A, Elizondo R. Effects of exercise-heat acclimation on fluid, electrolyte, and endocrine responses during tilt and+ Gz acceleration in women and men. Aviat Space Environ Med. 1985;56(7):683-689.
27. Schwellnus M, Nicol J, Laubscher R, Noakes T. Serum electrolyte concentrations and hydration status are not associated with exercise associated muscle cramping (EAMC) in distance runners. Br J Sports Med. 2004;38(4):488-492.
28. Van Beaumont W, Underkofler S, Van Beaumont S. Erythrocyte volume, plasma volume, and acid-base changes in exercise and heat dehydration. J Appl Physiol Respir Environ Exerc Physiol. 1981;50(6):1255-1262.
29. Saat M, Sirisinghe RG, Singh R, Tochihara Y. Effects of short-term exercise in the heat on thermoregulation, blood parameters, sweat secretion and sweat composition of tropic-dwelling subjects. J Physiol Anthropol Appl Human Sci. 2005;24(5):541-549.
Article Sidebar
Article Details
This work is licensed under a Creative Commons Attribution 4.0 International License.
Copyright, 2025 by the authors. This work is licensed under the Creative Commons Attribution 4.0 International License.