The Persistence of Heat Acclimatization in Man

Henschel, Austin; Taylor, Henry L.; Keys, Ancel

doi:10.1152/ajplegacy.1943.140.3.321

Cited by 28 publications

(22 citation statements)

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“…Although heat acclimation in a dry environment confers a substantial advantage in humid heat, the physiological and biophysical differences between dry and humid heat lead one to expect that humid heat acclimation would produce somewhat different physiological adaptations from dry heat acclimation. Early investigations supported this premise, indicating that dry heat acclimation might be better retained than humid heat acclimation (Bean & Eichna, 1943;Henschel et al, 1943;Robinson et al, 1943;Lind & Bass, 1963). Fox et al (1964) compared the effects of acclimation to dry and to humid heat on the inhibition of sweating using controlled hyperthermia (∼38.2°C core temperature).…”

Section: Acclimation To Dry and Humid Environmentsmentioning

confidence: 99%

Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports

Périard

Racinais

Sawka

2015

Scandinavian Med Sci Sports

422

486

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Exercise heat acclimation induces physiological adaptations that improve thermoregulation, attenuate physiological strain, reduce the risk of serious heat illness, and improve aerobic performance in warm-hot environments and potentially in temperate environments. The adaptations include improved sweating, improved skin blood flow, lowered body temperatures, reduced cardiovascular strain, improved fluid balance, altered metabolism, and enhanced cellular protection. The magnitudes of adaptations are determined by the intensity, duration, frequency, and number of heat exposures, as well as the environmental conditions (i.e., dry or humid heat).Evidence is emerging that controlled hyperthermia regimens where a target core temperature is maintained, enable more rapid and complete adaptations relative to the traditional constant work rate exercise heat acclimation regimens. Furthermore, inducing heat acclimation outdoors in a natural field setting may provide more specific adaptations based on direct exposure to the exact environmental and exercise conditions to be encountered during competition. This review initially examines the physiological adaptations associated with heat acclimation induction regimens, and subsequently emphasizes their application to competitive athletes and sports.

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Section: Acclimation To Dry and Humid Environmentsmentioning

confidence: 99%

Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports

Périard

Racinais

Sawka

2015

Scandinavian Med Sci Sports

422

486

View full text Add to dashboard Cite

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“…However, although it is accepted that the benefits of HA are transient and disappear if not maintained by repeated exposure to heat stress, studies investigating the nature of HA decay are relatively sparse and have yielded conflicting results (Pandolf 1998). Some papers have reported significant HA decay in less than 1 week (Adam et al 1960;Wyndham and Jacobs 1957), while others have shown that the physiological adaptations are relatively well maintained for up to 3 weeks (Robinson et al 1943;Henschel et al 1943;Lind and Bass 1963;Pandolf et al 1977). Pandolf (1998) noted that the pre-1963 studies were flawed in terms of experimental design and methodology, although subsequent more robust studies have yielded further conflicting results.…”

Section: Introductionmentioning

confidence: 99%

Quantification of the decay and re-induction of heat acclimation in dry-heat following 12 and 26 days without exposure to heat stress

et al. 2007

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Compared with the induction of heat acclimation (HA), studies investigating the decay and re-induction of HA (RA) are relatively sparse and have yielded conflicting results. Therefore, 16 semi-nude men were acclimated to dry-heat by undertaking an exercise protocol in a hot chamber (dry-bulb temperature 46.1 +/- 0.1 degrees C; relative humidity 17.9 +/- 0.1%) on 10 consecutive days (HA1-10) in winter UK. Thereafter, the subjects were divided into two groups and re-exposed to the work-in-heat tests after 12 and 26 days until RA was attained (RA(12), n = 8; RA(26), n = 8). The exercise protocol consisted of 60 min of treadmill walking (1.53 m s(-1)) at an incline individually set to induce a rectal temperature (T (re)) of approximately 38.5 degrees C during HA1 (equating to 45 +/- 4% peak oxygen uptake), followed by 10 min of rest and 40 min of further treadmill exercise, the intensity of which was increased across HA to maintain T(re )at approximately 38.5 degrees C. T(re), mean skin temperature, heart rate and rate of total water loss measured at 60 min did not change after HA7, and HA was taken as the mean of the responses during HA8-10. For both groups, there was no decay in T(re) and for all measured variables RA was attained after 2 and 4 days in RA(12) and RA(26), respectively. It is concluded that once adaptation to heat has been attained, the time that individuals may spend in cooler conditions before returning to a hot environment could be as long as one month, without the need for extensive re-adaptation to heat.

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“…Only a few studies have reported on the decay of HA when individuals stop working in hot environments (Bean and Eichna 1943;Lind and Bass 1963;Wyndham and Jacobs 1957;Adam et al 1960;Henschel et al 1943;Pandolf et al 1977;Williams et al 1967). Following a review of these studies, Givoni and Goldman (1973) tentatively suggested that the rate of decay of HA is such that for every 2 days spent without working in the heat, 1 day of acclimatization status is lost.…”

Section: Introductionmentioning

confidence: 99%

“…Following a review of these studies, Givoni and Goldman (1973) tentatively suggested that the rate of decay of HA is such that for every 2 days spent without working in the heat, 1 day of acclimatization status is lost. However, the data presented in several of the earlier studies are based on very small samples (n=1 or 2), incomplete acclimation, or brief decay periods (Bean and Eichna 1943;Lind and Bass 1963;Wyndham and Jacobs 1957;Adam et al 1960;Henschel et al 1943). In the study by Williams et al (1967) the decay of HA was investigated in three groups of 20 subjects for periods of 1, 2 and 3 weeks in cool conditions.…”

Section: Introductionmentioning

confidence: 99%

Decay of heat acclimation during exercise in cold and exposure to cold environment

et al. 2005

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Sixteen male students exercised for 14 days (1 h/day) in the heat for heat acclimation (HA). During deacclimation (DA) one group exercised in the cold (EXG, n=8) for 60 min/day (morning) and was exposed to the cold for another hour (afternoon) for 14 days. The other group was exposed to the cold (EPG, n=8) for 1 h each in the morning and afternoon (Ta: 18.0 degrees C, RH: 58%) over the same period. All returned to exercise in the heat for reacclimation (RA) for 10 days. Subjects were tested on days 1, 16, 21, 32, 36 and 44 on a bicycle ergometer for 60 min at 60% of VO(2max) in the heat (Ta: 31.1 degrees C, RH: 70%). Rectal temperature (T (re)) and heart rate (HR) at 40 min of exercise were used to determine the decay/gain of HA, which was calculated using the formula described by Pandolf et al. (Ergonomics, 20:399-408, 1977). After HA (day 16) T (re) and HR decreased significantly. During DA, EXG showed decay in T (re) of 24 and 35% and HR of 29 and 35% on days 21 and 32, respectively. For EPG the corresponding decay was of 2 and 9% for T (re) and 17 and 17% for HR. After 10 days of RA, EXG showed gains of 11% in T (re) and 12% in HR, while EPG showed gains of 47% in T (re) and 38% in HR. In conclusion, EXG had greater decay during DA and lower gains in RA compared to EPG. However, the differences between groups were significant only for T (re) after 4 days of DA.

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The Persistence of Heat Acclimatization in Man

Cited by 28 publications

References 0 publications

Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports

Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports

Quantification of the decay and re-induction of heat acclimation in dry-heat following 12 and 26 days without exposure to heat stress

Decay of heat acclimation during exercise in cold and exposure to cold environment

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