Acclimatization of older men to work in heat

Robinson, Sarah; Belding, Harwood S.; Consolazio, F. C.; Horvath, Steven M.; Turrell, Eugene S.

doi:10.1152/jappl.1965.20.4.583

Cited by 43 publications

(17 citation statements)

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“…This was proved by the same four men in this study who were evaluated [40°C, 25% relative humidity (RH)] when they averaged 31 and 52 yr of age and showed that heat tolerance was approximately the same at both times of testing (22). More recently, studies emphasize the importance of aerobic fitness and physical characteristics such as body fat and body weight in maintaining work-heat tolerance with aging (21).…”

supporting

confidence: 57%

“…In 1965, Robinson et al (22) were the first to imply that "habitually active" middle-aged men displayed the same acute exercise-heat tolerance and acclimated to heat at about the same rate and degree as when they were younger. This was proved by the same four men in this study who were evaluated [40°C, 25% relative humidity (RH)] when they averaged 31 and 52 yr of age and showed that heat tolerance was approximately the same at both times of testing (22).…”

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confidence: 99%

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Aging and assessment of physiological strain during exercise-heat stress

Moran

Kenney

Pierzga

et al. 2002

American Journal of Physiology-Regulatory, Integrative and Comp

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. Aging and assessment of physiological strain during exercise-heat stress. Am J Physiol Regulatory Integrative Comp Physiol 282: R1063-R1069, 2002 10.1152/ajpregu.00364.2001.-The purpose of this study was to evaluate the physiological strain index (PSI) for different age groups during exercise-heat stress (EHS). PSI was applied to three different databases. First, from young and middle-age men (21 Ϯ 2 and 46 Ϯ 5 yr, respectively) matched (n ϭ 9 each, P Ͼ 0.05) for maximal aerobic power. Subjects were heat acclimated by daily treadmill walking for two 50-min bouts separated by 10-min rest for 10 days in a hot-dry environment [49°C, 20% relative humidity (RH)]. The second database involved a group (n ϭ 8) of young (YA) and a group (n ϭ 7) of older (OA) men (26 Ϯ 1 and 69 Ϯ 1 yr, respectively) who underwent 16 wk of aerobic training and two control groups (n ϭ 7 each) who were matched for age to YA and OA. These four groups performed EHS at 36°C, 40% RH on a cycle ergometer for 60 min at 60% maximal aerobic power before and after training. The third database was obtained from three groups of postmenopausal women and a group of 10 men. Two groups of women (n ϭ 8 each) were undergoing hormone replacement therapy, estrogen or estrogen plus progesterone, and the third group (n ϭ 9) received no hormone replacement. Subjects were over 50 yr and performed the same EHS: exercising at 36°C, 40% RH on a cycle ergometer for 60 min. PSI assessed the strain for all three databases and reported differences were significant at P Ͻ 0.05. This index rated the strain in rank order, whereas the postacclimation and posttraining groups were assessed as having less strain than the preacclimation and pretraining groups. Furthermore, middle-aged women on estrogen replacement therapy had less strain than estrogen ϩ progesterone and no hormone therapy. PSI evaluation was extended for men and women of different ages (50-70 yr) during acute EHS, heat acclimation, after aerobic training, and inclusive of women undergoing hormone replacement therapy. esophageal temperature; heart rate; predictive indexes; rectal temperature COLLECTIVELY, THE LITERATURE on heat tolerance for the general population suggests that middle-aged and older men and women are more exercise-heat intolerant, suffering more physiological strain during exposure to a hot environment than younger individuals (6, 27). Older men and women have been reported to have higher heart rates (HR), higher mean skin and core (T c ) temperatures, and lower sweat rates than younger men and women during exercise-heat stress (EHS). However, it is unclear from these studies whether the exercise-heat intolerance observed with aging was related to age per se or associated with other factors such as certain disease states, decreased physical activity, and/or lowered aerobic fitness (21).In 1965, Robinson et al. (22) were the first to imply that "habitually active" middle-aged men displayed the same acute exercise-heat tolerance and acclimated to heat at about the same rate and degree as when th...

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supporting

confidence: 57%

mentioning

confidence: 99%

Aging and assessment of physiological strain during exercise-heat stress

Moran

Kenney

Pierzga

et al. 2002

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Whether older persons have a reduced capacity for acclimation or acclimatization to heat has not been resolved (Robinson et al 1965;Wagner et al 1972;Pandolf et al 1988;Armstrong and Kenney 1993;Inoue et al 1995). Pandolf et al (1988) performed a heat acclimation study using middle-aged and younger men of similar aerobic fitness and other physical characteristics and found little impairment of the thermoregulatory system, at least through the fifth decade of life for physically well-trained middle-aged men.…”

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confidence: 99%

Exercise- and methylcholine-induced sweating responses in older and younger men: effect of heat acclimation and aerobic fitness

Inoue¹,

Havenith

Kenney

et al. 1999

International Journal of Biometeorology

134

143

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The purpose of this investigation was to examine the effects of aging and aerobic fitness on exercise- and methylcholine-induced sweating responses during heat acclimation. Five younger [Y group-age: 23 +/- 1 (SEM) years; maximal oxygen consumption (VO2max): 47 +/- 3 ml.kg-1.min-1], four highly fit older (HO group- 63 +/- 3 years; 48 +/- 4 ml.kg-1.min-1) and five normally fit older men (NO group -67 +/- 3 years; 30 +/- 1 ml.kg-1.min-1) who were matched for height, body mass and percentage fat, were heat acclimated by daily cycle exercise (approximately 35% VO2max for 90 min) in a hot (43 degrees C, 30% RH) environment for 8 days. The heat acclimation regimen increased performance time, lowered final rectal temperature (Tre) and percentage maximal heart rate (%HRmax), improved thermal comfort and decreased sweat sodium concentration similarly in all groups. Although total body sweating rates (Msw) during acclimation were significantly greater in the Y and HO groups than in the NO group (P < 0.01) (because of the lower absolute workload in the NO group), the Msw did not change in all groups with the acclimation sessions. Neither were local sweating rates (msw) on chest, back, forearm and thigh changed in all groups by the acclimation. The HO group presented greater forearm msw (30-90 min) values and the Y group had greater back and thigh msw (early in exercise) values, compared to the other groups (P < 0.001). In a methylcholine injection test on days immediately before and after the acclimation, the order of sweat output per gland (SGO) on chest, back and thigh was Y > HO > NO, and on the forearm Y = HO > NO. No group differences were observed for activated sweat gland density at any site. The SGO at the respective sites increased in the post-acclimation test regardless of group (P < 0.01), but on the thigh the magnitude of the increase was lower in the NO (P < 0.02) and HO (P = 0.07) groups than in the Y group. These findings suggest that heat tolerance and the improvement with acclimation are little impaired not only in highly fit older but also normally fit older men, when the subjects exercised at the same relative exercise intensity. Furthermore, the changes induced by acclimation appear associated with an age-related decrease in VO2max. However methylcholine-activated SGO and the magnitude of improvement of SGO with acclimation are related not only to VO2max but also to aging, suggesting that sensitivity to cholinergic stimulation decreases with aging.

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“…Nevertheless, these older men exhibited about the same degree of overall strain during exercise in the heat as they did 21 years earlier, and acclimated aoout as well (27); however, these individuals may not be "typical" old men because of their habitually active lifestyles. More definitive research is needed to advance our understanding of exercise in the heat and its interaction with aging.…”

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confidence: 77%