European Journal of Applied Physiology

, Volume 112, Issue 1, pp 295–307 | Cite as

Short-term exercise-heat acclimation enhances skin vasodilation but not hyperthermic hyperpnea in humans exercising in a hot environment

  • Naoto Fujii
  • Yasushi Honda
  • Takeshi Ogawa
  • Bun Tsuji
  • Narihiko Kondo
  • Shunsaku Koga
  • Takeshi Nishiyasu
Original Article

Abstract

We tested the hypothesis that short-term exercise-heat acclimation (EHA) attenuates hyperthermia-induced hyperventilation in humans exercising in a hot environment. Twenty-one male subjects were divided into the two groups: control (C, n = 11) and EHA (n = 10). Subjects in C performed exercise-heat tests [cycle exercise for ~75 min at 58% \( \dot{V}_{{{\text{O}}_{{ 2 {\text{peak}}}} }} \) (37°C, 50% relative humidity)] before and after a 6-day interval with no training, while subjects in EHA performed the tests before and after exercise training in a hot environment (37°C). The training entailed four 20-min bouts of exercise at 50% \( \dot{V}_{{{\text{O}}_{{ 2 {\text{peak}}}} }} \) separated by 10 min of rest daily for 6 days. In C, comparison of the variables recorded before and after the no-training period revealed no changes. In EHA, the training increased resting plasma volume, while it reduced esophageal temperature (Tes), heart rate at rest and during exercise, and arterial blood pressure and oxygen uptake (\( \dot{V}_{{{\text{O}}_{2} }} \)) during exercise. The training lowered the Tes threshold for increasing forearm vascular conductance (FVC), while it increased the slope relating FVC to Tes and the peak FVC during exercise. It also lowered minute ventilation (\( \dot{V}_{\text{E}} \)) during exercise, but this effect disappeared after removing the influence of \( \dot{V}_{{{\text{O}}_{2} }} \) on \( \dot{V}_{\text{E}} \). The training did not change the slope relating ventilatory variables to Tes. We conclude that short-term EHA lowers ventilation largely by reducing metabolism, but it does not affect the sensitivity of hyperthermia-induced hyperventilation during submaximal, moderate-intensity exercise in humans.

Keywords

Adaptation to heat Body temperature Respiration Thermoregulation 

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Naoto Fujii
    • 1
  • Yasushi Honda
    • 1
  • Takeshi Ogawa
    • 1
    • 2
  • Bun Tsuji
    • 1
  • Narihiko Kondo
    • 3
  • Shunsaku Koga
    • 4
  • Takeshi Nishiyasu
    • 1
  1. 1.Institute of Health and Sports ScienceUniversity of TsukubaTsukubaJapan
  2. 2.Faculty of EconomicsTokuyama UniversityYamaguchiJapan
  3. 3.Faculty of Human DevelopmentKobe UniversityKobeJapan
  4. 4.Applied Physiology LaboratoryKobe Design UniversityKobeJapan

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