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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

Abstract

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.

Keywords

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

Notes

Acknowledgments

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.

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

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

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