Physiologic tolerance to uncompensable heat: intermittent exercise, field vs laboratory

Sawka, Michael N.; Latzka, W. A.; Montain, Scott J.; Cadarette, Bruce S.; Kolka, Margaret A.; Kraning, Kenneth K.

doi:10.1097/00005768-200103000-00014

Cited by 91 publications

(81 citation statements)

References 24 publications

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“…A core temperature of 38°C was selected as an approximate minimum for intolerance (29), as it was well enough below (Ϫ1.5°C) our laboratory safety threshold to allow an ample time ϫ temperature interaction for AUC calculation, which is a more accurate index of total heat strain than peak body temperature (14).…”

Section: Heat Acclimationmentioning

confidence: 99%

Exercise-heat acclimation in humans alters baseline levels and ex vivo heat inducibility of HSP72 and HSP90 in peripheral blood mononuclear cells

McClung¹,

Hasday²,

He³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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107

139

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McClung JP, Hasday JD, He J, Montain SJ, Cheuvront SN, Sawka MN, Singh IS. Exercise-heat acclimation in humans alters baseline levels and ex vivo heat inducibility of HSP72 and HSP90 in peripheral blood mononuclear cells. Am J Physiol Regul Integr Comp Physiol 294: R185-R191, 2008. First published October 31, 2007 doi:10.1152/ajpregu.00532.2007.-The induction of cellular acquired thermal tolerance (ATT) during heat acclimation (HA) in humans is not well described. This study determined whether exercise-HA modifies the human heat shock protein (HSP)72 and HSP90 responses and whether changes are correlated with physiological adaptations to HA. Using a 10-day HA protocol comprising daily exercise (treadmill walking) in a hot environment (T a ϭ 49°C, 20% RH), we analyzed baseline and ex vivo heat-induced expression of HSP72 and HSP90 in peripheral blood mononuclear cells (PBMCs) isolated prior to exercise from eight subjects on day 1 and 10 of the HA protocol. Classical physiological responses to HA were observed, including significantly reduced heart rate and core body temperature, and significantly increased sweating rate. Baseline levels of HSP72 and HSP90 were significantly increased following acclimation by 17.7 Ϯ 6.1% and 21.1 Ϯ 6.5%, respectively. Ex vivo induction of HSP72 in PBMCs exposed to heat shock (43°C) was blunted on day 10 compared with day 1. A correlation was identified (r 2 ϭ 0.89) between changes in core temperature elevation and ex vivo HSP90 responses to heat shock between days 1 and 10, indicating that volunteers demonstrating the greatest physiological HA tended to exhibit the greatest blunting of ex vivo HSP induction in response to heat shock. In summary, 1) exercise-HA resulted in increased baseline levels of HSP72 and HSP90, 2) ex vivo heat inducibility of HSP72 was blunted after HA, and 3) volunteers demonstrating the greatest physiological HA tended to exhibit the greatest blunting of ex vivo HSP induction in response to heat shock. These data demonstrate that physiological adaptations in humans undergoing HA are accompanied by both increases in baseline levels and changes in regulation of cytoprotective HSPs. stress; hyperthermia; adaptation; exertional tolerance HEAT ACCLIMATION (HA) REFERS to biological adaptations that reduce physiological strain (e.g., heart rate and body temperature), improve comfort, and improve physical exercise capabilities after repeated days of heat exposure (28, 30). Acquired thermal tolerance (ATT) refers to the cellular changes induced by repeated exposure to heat that confer cytoprotection against subsequent, more extreme, and potentially lethal heat exposure (11,17,33). For example, rodents with fully developed ATT can survive a 60% greater heat load compared with heat-naïve animals (21). Heat acclimation and ATT are complementary with the former reducing physiological strain and the latter providing cellular protection against serious heat injury for any degree of physiological strain. Few studies have examined the coincident induction of HA and ATT ...

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Section: Heat Acclimationmentioning

confidence: 99%

Exercise-heat acclimation in humans alters baseline levels and ex vivo heat inducibility of HSP72 and HSP90 in peripheral blood mononuclear cells

McClung¹,

Hasday²,

He³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

Self Cite

107

139

View full text Add to dashboard Cite

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“…Miles 1957;Pedoto et al 2003) or hypothermal or hyperthermal atmospheres (see e.g. Sawka et al 2001;Solonin and Katsyuba 2003). So, what about gravity and humans?…”

Section: A Large Radius Human Centrifugementioning

confidence: 99%

The Human Centrifuge

Loon

2008

Microgravity Sci. Technol

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Life on Earth has developed at unit gravity, 9.81 m/s 2 , which was a major factor especially when vertebrates emerged from water onto land in the late Devonian, some 375 million years ago. But how would nature have evolved on a larger planet? We are able to address this question simply in experiments using centrifuges. Based on these studies we have gained valuable insights in the physiological process in plants and animals. They adapt to a new steady state suitable for the high-g environments applied. Information on mammalian adaptations to hyper-g is interesting or may be even vital for human space exploration programs. It has been shown in long duration animal hypergravity studies, ranging from snails, rats to primates, that various structures like muscles, bones, neuro-vestibular, or the cardio-vascular system are affected. However, humans have never been exposed to a hyper-g environment for long durations. Centrifuge studies involving humans are mostly in the order of hours. The current work on human centrifuges are all focused on short arm systems to apply short periods of artificial gravity in support of long duration space missions in ISS or to Mars. In this paper we will address the possible usefulness of a large human centrifuge on Earth. In such a centrifuge a group of humans can be exposed to hypergravity for, in principle, an unlimited period of time like living on a larger planet. The input from a survey under scientists

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“…Another, important, advantage of the temperature pill is the suitability in fieldbased situations, which is of great importance since exercise-induced elevations in Tc are generally higher in field than in laboratory settings 16 . Currently, the temperature pill is able to measure the Tgi every 10 sec with an accuracy of ±0.1°C, which makes this technique very suitable to measure the Tgi during an exercise event or an important match.…”

Section: Introductionmentioning

confidence: 99%

Using an Ingestible Telemetric Temperature Pill to Assess Gastrointestinal Temperature During Exercise

Bongers

Hopman

Eijsvogels

2015

JoVE

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Exercise results in an increase in core body temperature (Tc), which may reduce exercise performance and eventually can lead to the development of heat-related disorders. Therefore, accurate measurement of Tc during exercise is of great importance, especially in athletes who have to perform in challenging ambient conditions. In the current literature a number of methods have been described to measure the Tc (esophageal, external tympanic membrane, mouth or rectum). However, these methods are suboptimal to measure Tc during exercise since they are invasive, have a slow response or are influenced by environmental conditions. Studies described the use of an ingestible telemetric temperature pill as a reliable and valid method to assess gastrointestinal temperature (Tgi), which is a representative measurement of Tc. Therefore, the goal of this study was to provide a detailed description of the measurement of Tgi using an ingestible telemetric temperature pill. This study addresses important methodological factors that must be taken into account for an accurate measurement. It is recommended to read the instructions carefully in order to ensure that the ingestible telemetric temperature pill is a reliable method to assess Tgi at rest and during exercise. Video LinkThe video component of this article can be found at

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Physiologic tolerance to uncompensable heat: intermittent exercise, field vs laboratory

Abstract: Exercise-rest cycles did not alter physiologic tolerance to UCHS. In addition, subjects from field studies demonstrate greater physiologic tolerance than subjects from laboratory studies.

Cited by 91 publications

References 24 publications

Exercise-heat acclimation in humans alters baseline levels and ex vivo heat inducibility of HSP72 and HSP90 in peripheral blood mononuclear cells

Exercise-heat acclimation in humans alters baseline levels and ex vivo heat inducibility of HSP72 and HSP90 in peripheral blood mononuclear cells

The Human Centrifuge

Using an Ingestible Telemetric Temperature Pill to Assess Gastrointestinal Temperature During Exercise

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