Pregnancy Exercises

Effects of Aging on Heat Tolerance

The investigations that have evaluated adults between the ages of and years suggest that middle-aged men and women are less tolerant of exercise-heat stress, and suffer greater physiological strain during heat acclimation, than younger individuals. Differences such as higher heart rates, higher skin and rectal temperatures, and lower sweat rates were reported in publications appearing between andHowever, none of these studies matched older and younger test subjects for pertinent physiological or morphological factors, such as body weight, surface area, body fat content, and VO hese factors, the resultant heat strain was similar. In fact, Pandolf and colleagues demonstrated that the exercise-heat tolerance of nine younger men mean age years was poorer than that of nine middle-aged men mean age years, in terms of tolerance time minutes of exercise at[F], rh to reach a rectal temperature of[F], final heart rate, sweat rate, and psychological rating of perceived exertion on the first day of a -day heat acclimation protocol. By dayhowever, there were few physiological differences between the age groups. Because the younger and older men had been pair-matched for all relevant physiological and morphological traits, the authors concluded that one factor probably resulted in the day differences: aerobic exercise training. The younger men averaged onlymi of running per week, while the middle-aged men ranmi each week. Therefore, cardiorespiratory physical fitness was more important than aging per se in determining the exercise-heat tolerance of these middle-aged men.

However, there may be one situation in which middle-aged and older men and women are more susceptible to greater heat strain. This involves physiologically significant dehydration of greater than of body weight. These same individuals also may not rehydrate as effectively as younger men and women, after dehydration.

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Most early studies of exercise-heat tolerance, regarding elderly adults years and older, were conducted on those who had chronic debilitating diseases such as coronary heart disease, diabetes mellitus, and Parkinson’s disease. It was evident that these elderly test subjects had a high incidence of heat intolerance, primarily involving underlying disease states, of which the most prominent was cardiovascular disease. Two studies, however, have observed healthy elderly test subjects. The first required that men and women, who ranged in age from to years, walk in the desert for at an exercise intensity of VOmax. The heat-acclimated, fit, healthy, elderly men and women had similar rectal temperature, heart rate, and sweat rate values as younger subjects. The second study evaluated six elderly men to years and ten young men to years who rested for up to min in a controlled environment

The healthy, elderly men exhibited no impairment of sweating ability, but apparently had a delayed vasodilation reflex in skin blood vessels, causing greater heat storage. Thus, when the effects of chronic debilitating diseases are kept to a minimum, the heat tolerance of the elderly does not appear to be greatly compromised. The exercise-heat tolerance of elderly adults has not been evaluated during strenuous, high-intensity exercise, however.

Medical Considerations The Heat Illnesses

Inthe World Health Organization recognized seven different heat illnesses, ranging from swelling edema of the feet and hands to life-threatening hyperthermia. Four of these illnesses, which occur among athletes and laborers, are described in tablepage : heat exhaustion, exertional heatstroke, heat cramps, and heat syncope. It is interesting that heat acclimatization reduces the incidence of all of these ailments.

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