Is Heat Intolerance State or Trait?
The existing literature suggests two standpoints in defining heat intolerance, which are heat tolerance as state or trait. The former bases its case in the plasticity of human physiology, where one may gain or lose the adaptations associated with heat acclimatization and the ability to tolerate heat is considered transient. This phenomenon is exemplified in the recovery process of exertional heat stroke (EHS) patients in that victims of EHS are able to eventually regain heat tolerance and return to activity without recurrent episodes of EHS. On the other hand, an increasing number of reports imply that genetic predisposition may be associated with one’s vulnerability to heat stress. Individuals who seem to exhibit lower than expected exercise tolerance in moderate heat and those who never regain heat tolerance post EHS fall into this category. However, there is a large area of uncertainty in this debate because a true prospective investigation of factors associated with heat intolerance is methodologically difficult. We conclude from the current literature that both mechanisms of heat intolerance (state and trait) should be considered in interpreting the mechanism and cause of heat intolerance.
Compliance with Ethical Standards
No sources of funding were used to assist in the preparation of this article.
Conflicts of Interest
Yuri Hosokawa has no conflict of interest associated with the submitted work. Rebecca L. Stearns has received royalties from Jones & Bartlett Learning. Douglas J. Casa has served as expert witness, received consulting honorarium from Clif Bar and Sports Innovation Labs, received funding from Gatorade, and royalties from Jones & Bartlett Learning, Lippincott Williams & Wilkins, Springer, and UpToDate. Rebecca L. Stearns and Douglas J. Casa are employee for the Korey Stringer Institute at the University of Connecticut.
Clinical documentation of the Hunter Knighton and Gavin Class exertional heat stroke cases in this article was approved by the Institutional Review Board at the University of Connecticut.
Consent was obtained from Hunter Knighton and Gavin Class to include their case details in this article.
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