Effectiveness of short-term heat acclimation on intermittent exercise in thermoneutral and hot environments

—The purpose of the present study was to determine the separate and combined effects of aerobic fitness, short-term heat acclimation, and hypohydration on tolerance during light exercise while wearing nuclear, biological, and chemical protective clothing in the heat (40°C, 30% relative humidity). Men who were moderately fit [(MF); <50 ml ⋅ kg−1 ⋅ min−1maximal O2 consumption; n = 7] and highly fit [(HF); >55 ml ⋅ kg−1 ⋅ min−1maximal O2 consumption; n = 8] were tested while they were euhydrated or hypohydrated by ∼2.5% of body mass through exercise and fluid restriction the day preceding the trials. Tests were conducted before and after 2 wk of daily heat acclimation (1-h treadmill exercise at 40°C, 30% relative humidity, while wearing the nuclear, biological, and chemical protective clothing). Heat acclimation increased sweat rate and decreased skin temperature and rectal temperature (Tre) in HF subjects but had no effect on tolerance time (TT). MF subjects increased sweat rate but did not alter heart rate, Tre, or TT. In both MF and HF groups, hypohydration significantly increased Tre and heart rate and decreased the respiratory exchange ratio and the TT regardless of acclimation state. Overall, the rate of rise of skin temperature was less, while ΔTre, the rate of rise of Tre, and the TT were greater in HF than in MF subjects. It was concluded that exercise-heat tolerance in this uncompensable heat-stress environment is not influenced by short-term heat acclimation but is significantly improved by long-term aerobic fitness.

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Differential stimulation of c-fos expression in hypothalamic nuclei of the rat brain during short-term heat acclimation and mild dehydration

Brain Research ◽

10.1016/s0006-8993(98)00405-3 ◽

1998 ◽

Vol 798 (1-2) ◽

pp. 127-139 ◽

Cited By ~ 56

Author(s):

Panagiotis Patronas ◽

Michal Horowitz ◽

Eckhart Simon ◽

Rüdiger Gerstberger

Keyword(s):

Rat Brain ◽

Heat Acclimation ◽

Short Term ◽

Hypothalamic Nuclei ◽

Fos Expression ◽

Stimulation Of

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THE INDUCTION AND DECAY OF SHORT-TERM HEAT ACCLIMATION

Medicine & Science in Sports & Exercise ◽

10.1097/00005768-200305001-00158 ◽

2003 ◽

Vol 35 (Supplement 1) ◽

pp. S30

Author(s):

A T. Garrett ◽

N G. Goossens ◽

N J. Rehrer ◽

M J. Patterson ◽

J D. Cotter

Keyword(s):

Heat Acclimation ◽

Short Term

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Impairment of Cycling Capacity in the Heat in Well-Trained Endurance Athletes After High-Intensity Short-Term Heat Acclimation

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2018-0537 ◽

2019 ◽

Vol 14 (8) ◽

pp. 1058-1065 ◽

Cited By ~ 9

Author(s):

Thomas Reeve ◽

Ralph Gordon ◽

Paul B. Laursen ◽

Jason K.W. Lee ◽

Christopher J. Tyler

Keyword(s):

High Intensity ◽

Interval Training ◽

Heat Acclimation ◽

Endurance Athletes ◽

Stress Tests ◽

High Intensity Interval Training ◽

Short Term ◽

High Intensity Interval ◽

C 50 ◽

Perceived Strain

Purpose: To investigate the effects of short-term, high-intensity interval-training (HIIT) heat acclimation (HA). Methods: Male cyclists/triathletes were assigned into either an HA (n = 13) or a comparison (COMP, n = 10) group. HA completed 3 cycling heat stress tests (HSTs) to exhaustion (60% Wmax; HST1, pre-HA; HST2, post-HA; HST3, 7 d post-HA). HA consisted of 30-min bouts of HIIT cycling (6 min at 50% Wmax, then 12 × 1-min 100%-Wmax bouts with 1-min rests between bouts) on 5 consecutive days. COMP completed HST1 and HST2 only. HST and HA trials were conducted in 35°C/50% relative humidity. Cycling capacity and physiological and perceptual data were recorded. Results: Cycling capacity was impaired after HIIT HA (77.2 [34.2] min vs 56.2 [24.4] min, P = .03) and did not return to baseline after 7 d of no HA (59.2 [37.4] min). Capacity in HST1 and HST2 was similar in COMP (43.5 [8.3] min vs 46.8 [15.7] min, P = .54). HIIT HA lowered resting rectal (37.0°C [0.3°C] vs 36.8°C [0.2°C], P = .05) and body temperature (36.0°C [0.3°C] vs 35.8°C [0.3°C], P = .03) in HST2 compared with HST1 and lowered mean skin temperature (35.4°C [0.5°C] vs 35.1°C [0.3°C], P = .02) and perceived strain on day 5 compared with day 1 of HA. All other data were unaffected. Conclusions: Cycling capacity was impaired in the heat after 5 d of consecutive HIIT HA despite some heat adaptation. Based on data, this approach is not recommended for athletes preparing to compete in the heat; however, it is possible that it may be beneficial if a state of overreaching is avoided.

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Short term heat acclimation reduces heat stress, but is not augmented by dehydration

Journal of Thermal Biology ◽

10.1016/j.jtherbio.2018.10.004 ◽

2018 ◽

Vol 78 ◽

pp. 227-234 ◽

Cited By ~ 5

Author(s):

Michael W. Schleh ◽

Brent C. Ruby ◽

Charles L. Dumke

Keyword(s):

Heat Stress ◽

Heat Acclimation ◽

Short Term

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Broadening human thermal comfort range based on short-term heat acclimation

Energy ◽

10.1016/j.energy.2019.04.007 ◽

2019 ◽

Vol 176 ◽

pp. 418-428 ◽

Cited By ~ 1

Author(s):

Daokun Chong ◽

Neng Zhu ◽

Wei Luo ◽

Zhiyu Zhang

Keyword(s):

Thermal Comfort ◽

Heat Acclimation ◽

Short Term ◽

Human Thermal Comfort

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Effects of adrenocorticotropin on temperature- and pressure-dependent metabolic functions

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1959.197.6.1291 ◽

1959 ◽

Vol 197 (6) ◽

pp. 1291-1296 ◽

Cited By ~ 8

Author(s):

Henry B. Hale ◽

Roy B. Mefferd

Keyword(s):

Barometric Pressure ◽

Male Rats ◽

Short Term ◽

Metabolic Functions ◽

Metabolic States ◽

Environmental Extremes ◽

Temperature And Pressure ◽

Hot Environments ◽

Low Dosage

Effects of adrenocorticotropin (ACTH) in low dosage on metabolic aspects were determined in adult male rats acclimated to cold, neutral or hot environments or to low barometric pressure. Urinary determinations provided the means for indirectly assessing metabolic states. The metabolic aspects studied were Na, K, Ca, P, Mg, urea, uric acid, creatinine, creatine, taurine, ß-alanine, glycine, α-alanine, valine, methionine, serine, threonine, tyrosine, glutamic acid, aspartic acid, lysine, arginine, histidine, glucose, glucuronic acid, phenolic acids and coproporphyrin. Additionally, fecal determinations were made for coproporphyrin, protoporphyrin and deuteroporphyrin. The interplay between endocrine and environmental factors and their importance to metabolic states during short-term and long-term exposures to environmental extremes thus received some clarification. With the low dosage employed, ACTH had a ‘restraining’ influence on nonspecific metabolic responses.

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Hypohydration and heat acclimation: plasma renin and aldosterone during exercise

Journal of Applied Physiology ◽

10.1152/jappl.1983.55.6.1790 ◽

1983 ◽

Vol 55 (6) ◽

pp. 1790-1794 ◽

Cited By ~ 26

Author(s):

R. P. Francesconi ◽

M. N. Sawka ◽

K. B. Pandolf

Keyword(s):

Environmental Conditions ◽

Plasma Levels ◽

Plasma Renin ◽

Heat Acclimation ◽

Renin Activity ◽

Hydration State ◽

Hot Environments

This study was designed to assess the effects of hydration, acclimation, environment, and exercise on plasma levels of renin and aldosterone. Sixteen subjects exercised (1.34 m X s-1), both pre- and postacclimation, when euhydrated or hypohydrated (-5% of body wt) in a comfortable (20 degrees C, rh = 40%), hot-wet (35 degrees C, rh = 79%), or hot-dry (49 degrees C, rh = 20%) environment. Although light exercise in a thermoneutral environment had no effects on plasma levels of renin activity (PRA) or aldosterone (ALD), exercise in both hot environments resulted in significantly increased levels of both. Increments in both PRA and ALD were greater when hypohydrated, and PRA effects were significantly moderated by heat acclimation in both the euhydration and hypohydration experiments. Although PRA and ALD responses were generally correlated, acclimation did not consistently attenuate ALD increments. We concluded that hydration state, acclimation level, and environmental conditions all affected the responses of PRA and ALD to light exercise.

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