Heat tolerance and aging.

Work-heat tolerance has been reported to be generally lower in middle-aged and elderly men and women than in younger men and women. Some authors have suggested that physically fit older men have fewer decrements in performance during work-heat stress than do less fit men of the same age. However, none of the studies matched older and younger individuals on any pertinent physiological or morphological variables. Recently, four different researchers have reported results of studies in which men or women differed in average age by 25 to 36 years but were matched for body weight, surface area, surface area: body weight ratio, percentage of body fat, and maximal aerobic power. Evidence from three of these studies indicated little impairment of the thermoregulatory system during acute work-heat stress or heat acclimation in these men and women, at least through the seventh decade of life. One of the four studies did indicate higher core temperatures and lower sweating rates in middle-aged women than in younger women after heat acclimation; however, the length of time the heat could be tolerated did not differ between these matched groups. These observations generally support the importance of aerobic fitness and other morphological factors to middle-aged and elderly individuals working or performing recreational activities in hot environments.