Short term heat acclimation reduces heat strain during a first, but not second, consecutive exercise-heat exposure. Issue 8 (August 2021)

• Record Type: Journal Article
• Authors: Pryor, Riana R.; Pryor, J. Luke; Vandermark, Lesley W.; Adams, Elizabeth L.; Brodeur, Rachel M.; Armstrong, Lawrence E.; Lee, Elaine C.; Maresh, Carl M.; Casa, Douglas J.
• Is Part Of: Journal of science and medicine in sport. Volume 24:Issue 8(2021)
• Page Start: 768
• Page End: 773
• Publication Date: 2021-08
• Subjects: Exercise -- Acclimatisation -- Consecutive days -- Subsequent exercise -- Rest; Sports sciences -- Periodicals; Sports medicine -- Periodicals; Exercise -- Physiological aspects -- Periodicals; Sports -- physiology -- Periodicals; Sports Medicine -- Periodicals; Sportgeneeskunde; 617.102705
• DOI: 10.1016/j.jsams.2021.03.020
• Languages: English
• ISSNs: 1440-2440

Abstract

Abstract: Objectives: Determine whether five days of heat acclimation reduces cardiovascular and thermoregulatory strain during consecutive exercise-heat exposures on the sixth day in the heat. Design: Pair-matched randomized control trial. Methods: Twenty-four males completed two, 120 min exercise sessions (Session 1, Session 2) in a single day before (Day 1) and after (Day 6) four additional days of exercise in either hot (HOT: 40 °C, 40% relative humidity, n = 16) or temperate (CON: 23 °C, 25% relative humidity, n = 8) environments. A mixed-methods heat acclimation approach was implemented. Day 2 consisted of 120 min of moderate-high intensity treadmill exercise. Days 3–5 consisted of 90 min of moderate-high intensity exercise, with HOT completing this in a hyperthermia clamped manner at rectal temperature ≥38.5 °C, and CON < 38.5 °C. Results: Session 1 end of exercise rectal temperature and heart rate were lower on Day 6 compared to Day 1 for HOT (p = 0.012, p = 0.003) but not CON (p = 0.152, p = 0.437). Session 2 end of exercise rectal temperature was not different between days for HOT (p = 0.104) or CON (p = 0.275). Session 2 end of exercise heart rate was lower on Day 6 compared to Day 1 for HOT (p = 0.004) and CON (p = 0.039). Session 1 sweat sensitivity was greater on Day 6 compared to Day 1 for HOT (p = 0.039) but not CON (p = 0.257). Sweat rate was unchanged for HOT and CON between days during Session 1 (p = 0.184, p = 0.962) and Session 2 (p = 0.051, p = 0.793), respectively. Conclusions: Five days of heat acclimation reduced cardiovascular strain but not thermoregulatory strain during the second, consecutive exercise-heat exposure. ClinicalTrials.gov Identifier: NCT04053465.