Exacerbated heat strain during consecutive days of repeated exercise sessions in heat

Riana R Pryor; J Luke Pryor; Lesley W Vandermark; Elizabeth L Adams; Rachel M Brodeur; Lawrence E Armstrong; Elaine C Lee; Carl M Maresh; Jeffrey M Anderson; Douglas J Casa

doi:10.1016/j.jsams.2019.06.003

Exacerbated heat strain during consecutive days of repeated exercise sessions in heat

J Sci Med Sport. 2019 Oct;22(10):1084-1089. doi: 10.1016/j.jsams.2019.06.003. Epub 2019 Jun 18.

Authors

Affiliations

¹ Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, SUNY, University at Buffalo, United States; Korey Stringer Institute, Department of Kinesiology, University of Connecticut, United States. Electronic address: rpryor@buffalo.edu.
² Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, SUNY, University at Buffalo, United States; Korey Stringer Institute, Department of Kinesiology, University of Connecticut, United States.
³ Korey Stringer Institute, Department of Kinesiology, University of Connecticut, United States; Exercise Science Research Center, Department of Health, Human Performance, and Recreation, University of Arkansas, United States.
⁴ Korey Stringer Institute, Department of Kinesiology, University of Connecticut, United States.
⁵ Department of Human Sciences, The Ohio State University, United States.

PMID: 31235386
DOI: 10.1016/j.jsams.2019.06.003

Abstract

Objectives: An exercise session in a hot environment may increase thermal strain during subsequent exercise sessions on the same and consecutive days. Therefore, this study was conducted to determine lasting physiological strain from moderate-high intensity, intermittent exercise in heat on subsequent exercise.

Design: Repeated measures laboratory study.

Methods: Seventeen healthy, recreationally active men (age: 22±3 y, maximal oxygen consumption: 54.6±5.3mLkg^-1min^-1) underwent two intermittent moderate-high intensity aerobic exercise sessions separated by 2h of rest one day, followed by one session 24h later in a 40°C, 40% relative humidity environment. Heart rate, rectal temperature, heat stress perception, and environmental symptoms were assessed.

Results: 100%, 35%, and 71% of participants completed the full exercise protocol during the first exercise session, second exercise session, and the following day, respectively. Exercising heart rate and rectal temperature were greater during the second exercise session (189±11bpm, 38.80±0.47°C) than the first identical exercise session (180±17bpm, p=0.004; 38.41±0.52°C, p=0.001), respectively. Immediate post-exercise heart rate, rectal temperature, thirst, thermal sensation, fatigue, and perceived exertion were similar among exercise sessions despite a shorter exercise duration during the second exercise session (93±27min, p=0.001) and the following day (113±12min, p=0.032) than the first exercise session (120±0min).

Conclusions: Moderate-high-intensity intermittent exercise in the heat resulted in greater heat strain during a second exercise session the same day, and exercise the subsequent day.

Keywords: Environment; Heat stress; Hydration; Thermoregulation.

MeSH terms

Adult
Body Temperature
Exercise*
Heart Rate
Heat-Shock Response*
Hot Temperature*
Humans
Male
Oxygen Consumption
Time Factors
Young Adult