Journal of Applied Physiology, Vol 65, Issue 1 65-71, Copyright © 1988 by American Physiological Society

ARTICLES

Thermoregulatory responses of middle-aged and young men during dry-heat acclimation

K. B. Pandolf, B. S. Cadarette, M. N. Sawka, A. J. Young, R. P. Francesconi and R. R. Gonzalez
United States Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760-5007.

Thermoregulatory responses during heat acclimation were compared between nine young (mean age 21.2 yr) and nine middle-aged men (mean age 46.4 yr) who were matched (P greater than 0.05) for body weight, surface area, surface area-to-weight ratio, percent body fat, and maximal aerobic power. After evaluation in a comfortable environment (22 degrees C, 50% relative humidity), the men were heat acclimated by treadmill walking (1.56 m/s, 5% grade) for two 50-min exercise bouts separated by 10 min of rest for 10 consecutive days in a hot dry (49 degrees C ambient temperature, 20% relative humidity) environment. During the first day of heat exposure performance time was 27 min longer (P less than 0.05) for the middle-aged men, whereas final rectal and skin temperatures and heart rate were lower, and final total body sweat loss was higher (P less than 0.05) compared with the young men. These thermoregulatory advantages for the middle-aged men persisted for the first few days of exercise-heat acclimation (P less than 0.05). After acclimation no thermoregulatory or performance time differences were observed between groups (P greater than 0.05). Sweating sensitivity, esophageal temperature at sweating onset, and the sweating onset time did not differ (P greater than 0.05) between groups either pre- or postacclimatization. Plasma osmolality and sodium concentration were slightly lower for the young men both pre- and postacclimatization; however, both groups had a similar percent change in plasma volume from rest to exercise during these tests.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				M. J. Buono, K. D. Ball, and F. W. Kolkhorst Sodium ion concentration vs. sweat rate relationship in humans J Appl Physiol, September 1, 2007; 103(3): 990 - 994. [Abstract] [Full Text] [PDF]

				B L Marks and S R Parsonage Health benefits for veteran (senior) tennis players * Commentary. Br. J. Sports Med., May 1, 2006; 40(5): 469 - 476. [Abstract] [Full Text] [PDF]

				D. S. Moran, W. L. Kenney, J. M. Pierzga, and K. B. Pandolf Aging and assessment of physiological strain during exercise-heat stress Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2002; 282(4): R1063 - R1069. [Abstract] [Full Text] [PDF]

				A. Takamata, T. Ito, K. Yaegashi, H. Takamiya, Y. Maegawa, T. Itoh, J. E. Greenleaf, and T. Morimoto Effect of an exercise-heat acclimation program on body fluid regulatory responses to dehydration in older men Am J Physiol Regulatory Integrative Comp Physiol, October 1, 1999; 277(4): R1041 - R1050. [Abstract] [Full Text] [PDF]

				S. S. Cheung and T. M. McLellan Heat acclimation, aerobic fitness, and hydration effects on tolerance during uncompensable heat stress J Appl Physiol, May 1, 1998; 84(5): 1731 - 1739. [Abstract] [Full Text] [PDF]

				M. J. Buono, J. H. Heaney, and K. M. Canine Acclimation to humid heat lowers resting core temperature Am J Physiol Regulatory Integrative Comp Physiol, May 1, 1998; 274(5): R1295 - R1299. [Abstract] [Full Text] [PDF]