European Journal of Applied Physiology

, Volume 111, Issue 6, pp 1197–1205 | Cite as

Does summer in a humid continental climate elicit an acclimatization of human thermoregulatory responses?

  • Anthony R. Bain
  • Ollie JayEmail author
Original Article


Many thermal physiologists follow the conventional wisdom that physiological heat adaptations occur in the summer for people living in a humid continental climate (e.g. Central Canada, North-eastern and Mid-western United States and Eastern Europe); therefore experimentation across seasons is often avoided. However, since modern behavioral adaptations, such as air conditioning, are accessible and commonplace, it is not clear whether such physiological adjustments actually do occur. It was hypothesized that despite warm weather, residing in a humid continental climate throughout a summer will not elicit any significant physiological heat adaptations since the environmental stimulus for such adjustments will be mitigated by behavioral adaptations. Eight young healthy male volunteers cycled at 60% VO2max for 90-min in a temperate environment before (mid-May) and at the end of (start of September) summer. Core temperature [measured in the esophagus (T es), rectum (T re) and aural canal (T au)], mean skin temperature (T sk), forearm skin blood flow (SkBf), upper back sweat rate (LSR) and heart rate (HR) were measured throughout exercise. Weekly activity logs and a lifestyle questionnaire were also administered throughout the summer months. No significant differences between pre- and end-summer were observed throughout exercise for T es (p = 0.565), T re (p = 0.350), T au (p = 0.261), T sk (p = 0.955), SkBf (p = 0.112), LSR (p = 0.394) or HR (p = 0.343). Likewise, the thermosensitivity and T es at the onset threshold for LSR (p = 0.177, p = 0.512) and SkBf (p = 0.805, p = 0.556) were also not significantly different. The apparent lack of heat acclimatization could be due to frequent air-conditioning use and an avoidance of outdoor activity during the hottest times of day but may also be due to a lack of environmental stimulus.


Seasonal acclimatization Core temperature Exercise Heat stress Physiological adaptations Skin blood flow Sweating 



This research was supported by a University of Ottawa, Faculty of Health Sciences Research Development Grant-Matched program and a Canadian Foundation for Innovation LOF Infrastructure Grant. Mr. Bain was supported by a University of Ottawa Master’s Scholarship and an Ontario Graduate Scholarship. The authors would like to thank the participants for volunteering for the study.


  1. Armstrong LE, Hubbard RW, DeLuca JP, Christensen EL (1987) Heat acclimatization during summer running in the northeastern United States. Med Sci Sports Exerc 19:131–136PubMedGoogle Scholar
  2. Bates GP, Miller VS (2008) Sweat rate and sodium loss during work in the heat. J Occup Med Toxicol 3:4PubMedCrossRefGoogle Scholar
  3. Canada S (2000) Commercial and Institutional Building Energy Use Survey. Statistics CanadaGoogle Scholar
  4. Canada S (2009) Dwelling Characteristics and Household Equipment for Canadian Provinces/Territories and Selected Metropolitan Areas. Statistics CanadaGoogle Scholar
  5. Chinevere TD, Kenefick RW, Cheuvront SN, Lukaski HC, Sawka MN (2008) Effect of heat acclimation on sweat minerals. Med Sci Sports Exerc 40:886–891PubMedCrossRefGoogle Scholar
  6. CSEP (1986) Canadian Society for Exercise Physiology:Certified Fitness Appraiser Resource Manual, Ottawa, ONGoogle Scholar
  7. Fox RH, Goldsmith R, Hampton IF, Hunt TJ (1967) Heat acclimatization by controlled hyperthermia in hot–dry and hot–wet climates. J Appl Physiol 22:39–46PubMedGoogle Scholar
  8. Havenith G, Luttikholt VG, Vrijkotte TG (1995) The relative influence of body characteristics on humid heat stress response. Eur J Appl Physiol Occup Physiol 70:270–279PubMedCrossRefGoogle Scholar
  9. Henane R, Bittel J (1975) Changes of thermal balance induced by passive heating in resting man. J Appl Physiol 38:294–299PubMedGoogle Scholar
  10. Ihzuka H, Hori S, Akamatsu T (1986) Seasonal variations of physiological responses to heat of subtropical and temperate natives. Int J Biometeorol 30:107–113PubMedCrossRefGoogle Scholar
  11. Inoue Y, Nakao M, Okudaira S, Ueda H, Araki T (1995) Seasonal variation in sweating responses of older and younger men. Eur J Appl Physiol Occup Physiol 70:6–12PubMedCrossRefGoogle Scholar
  12. Kondo N, Takano S, Aoki K, Shibasaki M, Tominaga H, Inoue Y (1998) Regional differences in the effect of exercise intensity on thermoregulatory sweating and cutaneous vasodilation. Acta Physiol Scand 164:71–78PubMedCrossRefGoogle Scholar
  13. Kruk J (2009) Physical activity and health. Asian Pac J Cancer Prev 10:721–728PubMedGoogle Scholar
  14. Marcus P (1972) Heat acclimatization by exercise-induced elevation of body temperature. J Appl Physiol 33:283–288PubMedGoogle Scholar
  15. Masterton J, Richardson F (1979) Humidex, a method of quantifying human discomfort due to excessive heat and humidity In: Environment Canada AES (ed), Downsview, Ontario, p. 45Google Scholar
  16. McMurray RG, Horvath SM (1979) Thermoregulation in swimmers and runners. J Appl Physiol 46:1086–1092PubMedGoogle Scholar
  17. Mekjavic IB, Rempel ME (1990) Determination of esophageal probe insertion length based on standing and sitting height. J Appl Physiol 69:376–379PubMedGoogle Scholar
  18. Moseley PL (1994) Mechanisms of heat adaptation: thermotolerance and acclimatization. J Lab Clin Med 123:48–52PubMedGoogle Scholar
  19. Nadel E (ed) (1977) Problems with temperature regulation during exercise. Academic Press, Inc, New York, NYGoogle Scholar
  20. Nagashima K (2006) Central mechanisms for thermoregulation in a hot environment. Ind Health 44:359–367PubMedCrossRefGoogle Scholar
  21. Nielsen B (1998) Heat acclimation—mechanisms of adaptation to exercise in the heat. Int J Sports Med 19(Suppl 2):S154–S156PubMedCrossRefGoogle Scholar
  22. Nielsen B, Hales JR, Strange S, Christensen NJ, Warberg J, Saltin B (1993) Human circulatory and thermoregulatory adaptations with heat acclimation and exercise in a hot, dry environment. J Physiol 460:467–485PubMedGoogle Scholar
  23. Pandolf KB, Cadarette BS, Sawka MN, Young AJ, Francesconi RP, Gonzalez RR (1988) Thermoregulatory responses of middle-aged and young men during dry–heat acclimation. J Appl Physiol 65:65–71PubMedGoogle Scholar
  24. Ramanathan NL (1964) A new weighting system for mean surface temperature of the human body. J Appl Physiol 19:531–533PubMedGoogle Scholar
  25. Roberts MF, Wenger CB, Stolwijk JA, Nadel ER (1977) Skin blood flow and sweating changes following exercise training and heat acclimation. J Appl Physiol 43:133–137PubMedGoogle Scholar
  26. Romanovsky AA (2007) Thermoregulation: some concepts have changed. Functional architecture of the thermoregulatory system. Am J Physiol Regul Integr Comp Physiol 292:R37–R46PubMedCrossRefGoogle Scholar
  27. Sawka MN, Young AJ, Francesconi RP, Muza SR, Pandolf KB (1985) Thermoregulatory and blood responses during exercise at graded hypohydration levels. J Appl Physiol 59:1394–1401PubMedGoogle Scholar
  28. Senay LC, Mitchell D, Wyndham CH (1976) Acclimatization in a hot, humid environment: body fluid adjustments. J Appl Physiol 40:786–796PubMedGoogle Scholar
  29. Shapiro Y, Hubbard RW, Kimbrough CM, Pandolf KB (1981) Physiological and hematologic responses to summer and winter dry–heat acclimation. J Appl Physiol 50:792–798PubMedGoogle Scholar
  30. Siri WE (1993) Body composition from fluid spaces and density: analysis of methods. 1961. Nutrition 9:480–491 (discussion 480, 492)PubMedGoogle Scholar
  31. Stapleton J, Gagnon D, Kenny GP (2010) Short-term exercise training does not improve whole-body heat loss when rate of metabolic heat production is considered. Eur J Appl Physiol 109:437–446PubMedCrossRefGoogle Scholar
  32. Taylor NA (2006) Challenges to temperature regulation when working in hot environments. Ind Health 44:331–344PubMedCrossRefGoogle Scholar
  33. Werner J (2009) System properties, feedback control and effector coordination of human temperature regulation. Eur J Appl Physiol 109:13–25PubMedCrossRefGoogle Scholar
  34. Wright HE, Selkirk GA, McLellan TM (2010) HPA and SAS responses to increasing core temperature during uncompensable exertional heat stress in trained and untrained males. Eur J Appl Physiol 108:987–997PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.Thermal Ergonomics Laboratory, School of Human KineticsUniversity of OttawaOttawaCanada

Personalised recommendations