scholarly journals The optimal exercise intensity for the unbiased comparison of thermoregulatory responses between groups unmatched for body size during uncompensable heat stress

2017 ◽  
Vol 5 (5) ◽  
pp. e13099 ◽  
Author(s):  
Nicholas Ravanelli ◽  
Matthew Cramer ◽  
Pascal Imbeault ◽  
Ollie Jay
Keyword(s):  
Heat Stress ◽  
Body Size ◽  
Exercise Intensity ◽  
Thermoregulatory Responses ◽  
Uncompensable Heat Stress

Physiological tolerance to uncompensable heat stress: effects of exercise intensity, protective clothing, and climate

1994 ◽  
Vol 77 (1) ◽  
pp. 216-222 ◽  
Author(s):  
S. J. Montain ◽  
M. N. Sawka ◽  
B. S. Cadarette ◽  
M. D. Quigley ◽  
J. M. McKay
Keyword(s):  
Heat Stress ◽  
Relative Humidity ◽  
Core Temperature ◽  
Exercise Intensity ◽  
Protective Clothing ◽  
Heat Exposure ◽  
Heat Strain ◽  
Published Data ◽  
Physiological Tolerance ◽  
Uncompensable Heat Stress

This study determined the influence of exercise intensity, protective clothing level, and climate on physiological tolerance to uncompensable heat stress. It also compared the relationship between core temperature and the incidence of exhaustion from heat strain for persons wearing protective clothing to previously published data of unclothed persons during uncompensable heat stress. Seven heat-acclimated men attempted 180-min treadmill walks at metabolic rates of approximately 425 and 600 W while wearing full (clo = 1.5) or partial (clo = 1.3) protective clothing in both a desert (43 degrees C dry bulb, 20% relative humidity, wind 2.2 m/s) and tropical (35 degrees C dry bulb, 50% relative humidity, wind 2.2 m/s) climate. During these trials, the evaporative cooling required to maintain thermal balance exceeded the maximal evaporative capacity of the environment and core temperature continued to rise until exhaustion from heat strain occurred. Our findings concerning exhaustion from heat strain are 1) full encapsulation in protective clothing reduces physiological tolerance as core temperature at exhaustion was lower (P < 0.05) in fully than in partially clothed persons, 2) partial encapsulation results in physiological tolerance similar to that reported for unclothed persons, 3) raising metabolic rate from 400 to 600 W does not alter physiological tolerance when subjects are fully clothed, and 4) physiological tolerance is similar when subjects are wearing protective clothing in desert and tropical climates having the same wet bulb globe thermometer. These findings can improve occupational safety guidelines for human heat exposure, as they provide further evidence that the incidence of exhaustion from heat strain can be predicted from core temperature.

Ten-day endurance training attenuates the hyperosmotic suppression of cutaneous vasodilation during exercise but not sweating

2005 ◽  
Vol 99 (1) ◽  
pp. 237-243 ◽  
Author(s):  
Takashi Ichinose ◽  
Kazunobu Okazaki ◽  
Shizue Masuki ◽  
Hiroyuki Mitono ◽  
Mian Chen ◽  
...  
Keyword(s):  
Endurance Training ◽  
Exercise Intensity ◽  
Plasma Osmolality ◽  
Young Male ◽  
Cycle Ergometer ◽  
Peak Oxygen Consumption ◽  
Cutaneous Vasodilation ◽  
Thermoregulatory Responses ◽  
Before And After ◽  
The Individual

It is well known that hyperosmolality suppresses thermoregulatory responses and that plasma osmolality (Posmol) increases with exercise intensity. We examined whether the decreased esophageal temperature thresholds for cutaneous vasodilation (THFVC) and sweating (THSR) after 10-day endurance training (ET) are caused by either attenuated increase in Posmol at a given exercise intensity or blunted sensitivity of hyperosmotic suppression. Nine young male volunteers exercised on a cycle ergometer at 60% peak oxygen consumption rate (V̇o2 peak) for 1 h/day for 10 days at 30°C. Before and after ET, thermoregulatory responses were measured during 20-min exercise at pretraining 70% V̇o2 peak in the same environment as during ET under isoosmotic or hyperosmotic conditions. Hyperosmolality by ∼10 mosmol/kgH2O was attained by acute hypertonic saline infusion. After ET, V̇o2 peak and blood volume (BV) both increased by ∼4% ( P < 0.05), followed by a decrease in THFVC ( P < 0.05) but not by that in THSR. Although there was no significant decrease in Posmol at the thresholds after ET, the sensitivity of increase in THFVC at a given increase in Posmol [ΔTHFVC/ΔPosmol,°C·(mosmol/kgH2O)−1], determined by hypertonic infusion, was reduced to 0.021 ± 0.005 from 0.039 ± 0.004 before ET ( P < 0.05). The individual reductions in ΔTHFVC/ΔPosmol after ET were highly correlated with their increases in BV around THFVC ( r = −0.89, P < 0.005). In contrast, there was no alteration in the sensitivity of the hyperosmotic suppression of sweating after ET. Thus the downward shift of THFVC after ET was partially explained by the blunted sensitivity to hyperosmolality, which occurred in proportion to the increase in BV.

Heat acclimation, aerobic fitness, and hydration effects on tolerance during uncompensable heat stress

1998 ◽  
Vol 84 (5) ◽  
pp. 1731-1739 ◽  
Author(s):  
Stephen S. Cheung ◽  
Tom M. McLellan
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Aerobic Fitness ◽  
Protective Clothing ◽  
Sweat Rate ◽  
Heat Acclimation ◽  
Short Term ◽  
Chemical Protective Clothing ◽  
Uncompensable Heat Stress ◽  
C 30

—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.

Effects of cold exposure and exercise intensity on metabolic and thermoregulatory responses

2020 ◽  
Vol 3 (5) ◽  
pp. 464-472
Author(s):  
Brittany Followay ◽  
Yongsuk Seo ◽  
Jeremiah Vaughan ◽  
Ellen L. Glickman ◽  
Adam R. Jajtner
Keyword(s):  
Cold Exposure ◽  
Exercise Intensity ◽  
Thermoregulatory Responses

Influence of Intermittent Hand Cooling and Fluid Replacement on Inflammatory Cytokines During Uncompensable Heat Stress

2015 ◽  
Vol 47 ◽  
pp. 460-461
Author(s):  
Robert A. Huggins ◽  
William M. Adams ◽  
Jenna M. Bartley ◽  
Colleen X. Munoz ◽  
J Luke Pryor ◽  
...  
Keyword(s):  
Heat Stress ◽  
Inflammatory Cytokines ◽  
Fluid Replacement ◽  
Uncompensable Heat Stress
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