The efficacy of weekly and bi-weekly heat training to maintain the physiological benefits of heat acclimation

Objectives: To examine the efficacy of weekly and bi-weekly heat training to maintain heat acclimatization (HAz) and heat acclimation (HA) for 8 weeks in aerobically trained athletes. Design: Randomized, between-group. Methods: Twenty-four males (mean [m +/- standard deviation [sd]; (age, 34 +/- 12 y; body mass, 72.6 +/- 8.8 kg, VO2peak, 57.7 +/- 6.8 mL.kg(-1).min(-1)) completed five trials (baseline, following HAz, following HA (HAz + HA), four weeks into heat training [HTWK4], and eight weeks into HT [HTWK8] that involved 60 min of steadystate exercise (59.1 +/- 1.8% vVO(2peak)) in an environmental laboratory (wet bulb globe temperature [WBGT], 29.6 +/- 1.4 degrees C) on a motorized treadmill. Throughout exercise, heart rate (HR) and rectal temperature (Trec) were recorded. Following HAz + HA, participants were assigned to three groups: control group (HT0), once per week heat training (HT1), and twice per week heat training (HT2). HT involved heated exercise (WBGT, 33.3 +/- 1.3 degrees C) to achieve hyperthermia (38.5-39.75 degrees C) for 60 min. Repeated measures ANOVAs were used to determine differences. Results: HAz + HA resulted in significant improvements in HR (p < 0.001) and Trec (p < 0.001). At HTWK8, HR was significantly higher in HT0 (174 +/- 22 beats.min-1) compared to HT2 (151 +/- 17 beats.min-1, p < 0.023), but was not different than HT1 (159 +/- 17 beats.min-1, p = 0.112). There was no difference in % change of Trec from postHAz + HA to HTWK4 (0.6 +/- 1.3%; p = 0.218), however, HTWK8 (1.8 +/- 1.4%) was significantly greater than postHAz + HA in HT0 (p = 0.009). Conclusions: Bi-weekly HT provided clear evidence for the ability to maintain physiological adaptions for 8 weeks following HA. (C) 2021 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Automated summary

Weekly or bi-weekly heat training can maintain heat acclimatization and heat acclimation in athletes for 8 weeks, leading to improved heart rate and body temperature.