A 5-day Heat Acclimation Program Improves Heat Stress Indicators While Maintaining Exercise Capacity

Floris C. Wardenaar, Carmen P. Ortega-Santos, Kaila A.S. Vento, Joshua S. Beaumont, Stephanie C. Griffin, Carol Johnston, Stavros A. Kavouras

Research output: Contribution to journalArticlepeer-review


This study aimed to evaluate whether a daily 60 minutes isothermic biking protocol during a 5-day period could improve physiological heat acclimation and exercise performance capacity in partially acclimated subjects. A quasi-experimental study consisted of an intervention (INT, n = 7) and control (CON, n = 7) group completing 2 12 minutes Cooper tests (pre-CT on day 1 and post-CT on day 7) and a heat stress test (HST, on day 9). INT performed additional intensive exercise 1 hour per day on days 1-5, whereas CON did not. During CTs and HST, core temperature (Tc, telemetric capsule), skin temperature (Tsk, sensors at neck, right shoulder, left hand, and right shin), and heart rate (HR, chest strap) were continuously monitored and baseline, average, peak, and increment were calculated. During the HST, the INT group showed a smaller baseline-peak Tcincrement (INT 0.88 ± 0.27 vs. CON 1.64 ± 0.90° C, p = 0.02), a lower HR peak (150.2 ± 12.6 vs. 173.0 ± 16.8 b·min-1, p = 0.02), and lower Tskpeak (36.47 ± 0.62 vs. 36.54 ± 0.46° C, p = 0.04). There was a nonsignificant, but practical difference based on a moderate effect size for change in pre-CT to post-CT performance of nearly +2.7 ± 12.3% in INT and -3.0 ± 8.5% in CON (p = 0.32 and d = 0.51), and HST distance covered resulting in a nonsignificant difference of 464 ± 849 m between INT and CON (p = 0.38 and d = 0.44). In conclusion a short-term 5-day heat acclimation program including 300 minutes of extra exercise resulted in positive physiological adaptions to heat stress, as indicated by lower core temperature and HR in comparison with a control group.

Original languageEnglish (US)
Pages (from-to)1279-1286
Number of pages8
JournalJournal of Strength and Conditioning Research
Issue number5
StatePublished - May 1 2021


  • heat adaptation
  • heat tolerance
  • hydration status
  • physical performance
  • sweat rate
  • thermoregulation

ASJC Scopus subject areas

  • Physical Therapy, Sports Therapy and Rehabilitation
  • Orthopedics and Sports Medicine


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