Is Heat Intolerance State or Trait?

  • Yuri HosokawaEmail author
  • Rebecca L. Stearns
  • Douglas J. Casa
Leading Article


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.

Ethical Approval

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.

Informed Consent

Consent was obtained from Hunter Knighton and Gavin Class to include their case details in this article.


  1. 1.
    Sawka MN, Leon LR, Montain SJ, Sonna LA. Integrated physiological mechanisms of exercise performance, adaptation, and maladaptation to heat stress. Compr Physiol. 2011;1:1883–928.CrossRefGoogle Scholar
  2. 2.
    Jay O, Kenny GP. The determination of changes in body heat content during exercise using calorimetry and thermometry. J Hum Environ Syst. 2007;10:19–29.CrossRefGoogle Scholar
  3. 3.
    Rowell LB. Human cardiovascular adjustments to exercise and thermal stress. Physiol Rev. 1974;54:75–159.CrossRefGoogle Scholar
  4. 4.
    Nadel ER, Cafarelli E, Roberts MF, Wenger CB. Circulatory regulation during exercise in different ambient temperatures. J Appl Physiol. 1979;46:430–7.CrossRefGoogle Scholar
  5. 5.
    Wingo JE, Crandall CG, Kenny GP. Chapter 2 Human Heat Physiology. In: Casa DJ, editor. Sport and physical activity in the heat—maximizing performance and safety. Berlin: Springer; 2018. p. 15–30.CrossRefGoogle Scholar
  6. 6.
    Nielsen M. Die Regulation der Körpertemperatur bei Muskelarbeit1. Skand Arch Für Physiol. 1938;79:193–230.CrossRefGoogle Scholar
  7. 7.
    Armstrong LE, Maresh CM. The Induction and decay of heat acclimatisation in trained athletes. Sports Med. 1991;12:302–12.CrossRefGoogle Scholar
  8. 8.
    Cramer MN, Jay O. Explained variance in the thermoregulatory responses to exercise: the independent roles of biophysical and fitness/fatness-related factors. J Appl Physiol Bethesda Md. 1985;2015(119):982–9.Google Scholar
  9. 9.
    Cheuvront SN, Kenefick RW. Dehydration: physiology, assessment, and performance effects. Compr Physiol. 2014;4:257–85.CrossRefGoogle Scholar
  10. 10.
    Racinais S, Alonso JM, Coutts AJ, Flouris AD, Girard O, González-Alonso J, et al. Consensus recommendations on training and competing in the heat. Br J Sports Med. 2015;49:1164–73.CrossRefGoogle Scholar
  11. 11.
    Casadio JR, Kilding AE, Cotter JD, Laursen PB. From lab to real world: heat acclimation considerations for elite athletes. Sports Med Auckl NZ. 2017;47:1467–76.CrossRefGoogle Scholar
  12. 12.
    Casa DJ, DeMartini JK, Bergeron MF, Csillan D, Eichner ER, Lopez RM, et al. National Athletic Trainers’ Association position statement: exertional heat illnesses. J Athl Train. 2015;50:986–1000.CrossRefGoogle Scholar
  13. 13.
    Belding HS, Kamon E. Evaporative coefficients for prediction of safe limits in prolonged exposures to work under hot conditions. Fed Proc. 1973;32:1598–601.Google Scholar
  14. 14.
    Sagui E, Montigon C, Abriat A, Jouvion A, Duron-Martinaud S, Canini F, et al. Is there a link between exertional heat stroke and susceptibility to malignant hyperthermia? PLoS ONE [Internet]. 2015. Accessed 2019 18 Jan 2019.
  15. 15.
    Shapiro Y, Magazanik A, Udassin R, Ben-Baruch G, Shvartz E, Shoenfeld Y. Heat intolerance in former heatstroke patients. Ann Intern Med. 1979;90:913–6.CrossRefGoogle Scholar
  16. 16.
    Stearns RL, Deuster PA, Kazman JB, Heled Y, O’Connor FG. Chapter 12 heat tolerance testing. In: Casa DJ, editor. Sport and physical activity in the heat—maximizing performance and safety. Berlin: Springer; 2018. p. 213–27.CrossRefGoogle Scholar
  17. 17.
    Fiszer D, Shaw M-A, Fisher NA, Carr IM, Gupta PK, Watkins EJ, et al. Next-generation sequencing of RYR1 and CACNA1S in malignant hyperthermia and exertional heat illness. Anesthesiology. 2015;122:1033–46.CrossRefGoogle Scholar
  18. 18.
    Potts LE, Longwell JJ, Bedocs P, Sambuughin N, Bina S, Cooper PB, et al. Improving awareness of nonanesthesia-related malignant hyperthermia presentations: a tale of two brothers. Case Rep. 2014;3:23–6.Google Scholar
  19. 19.
    Muldoon S, Deuster P, Voelkel M, Capacchione J, Bunger R. Exertional heat illness, exertional rhabdomyolysis, and malignant hyperthermia: is there a link? Curr Sports Med Rep. 2008;7:74–80.CrossRefGoogle Scholar
  20. 20.
    Hosokawa Y, Casa DJ, Rosenberg H, Capacchione JF, Sagui E, Riazi S, et al. Round table on malignant hyperthermia in physically active populations: meeting proceedings. J Athl Train. 2017;52:377–83.CrossRefGoogle Scholar
  21. 21.
    Keren G, Epstein Y, Magazanik A. Temporary heat intolerance in a heatstroke patient. Aviat Sp Environ Med. 1981;52:116–7.Google Scholar
  22. 22.
    Druyan A, Yanovich R, Heled Y. Misdiagnosis of exertional heat stroke and improper medical treatment. Mil Med. 2011;176:1278–80.CrossRefGoogle Scholar
  23. 23.
    Adams WM, Hosokawa Y, Huggins RA, Mazerolle SM, Casa DJ. An exertional heat stroke survivor’s return to running: an integrated approach on the treatment, recovery, and return to activity. J Sport Rehabil. 2016;25:280–7.CrossRefGoogle Scholar
  24. 24.
    Chen S-H, Lin M-T, Chang C-P. Ischemic and oxidative damage to the hypothalamus may be responsible for heat stroke. Curr Neuropharmacol. 2013;11:129–40.CrossRefGoogle Scholar
  25. 25.
    Leon LR, Bouchama A. Heat stroke. Compr Physiol. 2015;5:611–47.CrossRefGoogle Scholar
  26. 26.
    Moran DS, Erlich T, Epstein Y. The heat tolerance test: an efficient screening tool for evaluating susceptibility to heat. J Sport Rehabil. 2007;16:215–21.CrossRefGoogle Scholar
  27. 27.
    Mee JA, Doust J, Maxwell NS. Repeatability of a running heat tolerance test. J Therm Biol. 2015;49–50:91–7.CrossRefGoogle Scholar
  28. 28.
    Stearns RL. True Story #4……. returning a complicated exertional heat stroke case to activity. In: Gorse K, Feld F, Blanc R, editors. True stories Athl Train Room. Thorofare: SLACK Inc; 2018.Google Scholar
  29. 29.
    Kenney WL. A review of comparative responses of men and women to heat stress. Environ Res. 1985;37:1–11.CrossRefGoogle Scholar
  30. 30.
    Kenney WL. Physiological correlates of heat intolerance. Sports Med Auckl NZ. 1985;2:279–86.CrossRefGoogle Scholar
  31. 31.
    Druyan A, Amit D, Makranz C, Moran D, Yanovich R, Epstein Y, et al. Heat tolerance in women—reconsidering the criteria. Aviat Sp Environ Med. 2012;83:58–60.CrossRefGoogle Scholar
  32. 32.
    Smoljanić J, Morris NB, Dervis S, Jay O. Running economy, not aerobic fitness, independently alters thermoregulatory responses during treadmill running. J Appl Physiol Bethesda Md. 1985;2014(117):1451–9.Google Scholar
  33. 33.
    Cramer MN, Jay O. Selecting the correct exercise intensity for unbiased comparisons of thermoregulatory responses between groups of different mass and surface area. J Appl Physiol Bethesda Md. 1985;2014(116):1123–32.Google Scholar
  34. 34.
    Nelson DA, Deuster PA, O’Connor FG, Kurina LM. Timing and predictors of mild and severe heat illness among new military enlistees. Med Sci Sports Exerc. 2018;50:1603–12.CrossRefGoogle Scholar
  35. 35.
    Stearns RL, Hosokawa Y, Adams WM, Belval LN, Huggins RA, Jardine JF, et al. Repeated exertional heat stroke incidence in a warm-weather road race. J Athl Train. 2017;52:S106.Google Scholar
  36. 36.
    Abriat A, Brosset C, Brégigeon M, Sagui E. Report of 182 cases of exertional heatstroke in the French Armed Forces. Mil Med. 2014;179:309–14.CrossRefGoogle Scholar
  37. 37.
    Sagui E. Malignant hyperthermia, exertional heat illness, and RYR1 variants: the muscle may not be the brain. Anesthesiology. 2016;124:510.CrossRefGoogle Scholar
  38. 38.
    Smith R, Jones N, Martin D, Kipps C. “Too much of a coincidence”: identical twins with exertional heatstroke in the same race. BMJ Case Rep. 2016;2016:bcr2015212592.CrossRefGoogle Scholar
  39. 39.
    Bouchama A, Knochel JP. Heat stroke. N Engl J Med. 2002;346:1978–88.CrossRefGoogle Scholar
  40. 40.
    Hashim IA. Clinical biochemistry of hyperthermia. Ann Clin Biochem. 2010;47:516–23.CrossRefGoogle Scholar
  41. 41.
    Heled Y, Fleischmann C, Epstein Y. Cytokines and their role in hyperthermia and heat stroke. J Basic Clin Physiol Pharmacol. 2013;24:85–96.Google Scholar
  42. 42.
    Horowitz M. Heat acclimation, epigenetics, and cytoprotection memory. Compr Physiol. 2014;4:199–230.CrossRefGoogle Scholar
  43. 43.
    Stearns RL, Casa DJ, O’Connor FG, Lopez RM. A tale of two heat strokes: a comparative case study. Curr Sports Med Rep. 2016;15:94–7.CrossRefGoogle Scholar
  44. 44.
    Casa DJ. Don’t gamble: complex considerations for return to play following exertional heat stroke. J Sport Rehabil. 2007;16:161–2.CrossRefGoogle Scholar

Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.College of Sport and Health ScienceRitsumeikan UniversityKusatsuJapan
  2. 2.Korey Stringer Institute, Department of KinesiologyUniversity of ConnecticutStorrsUSA

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