Eccentric muscle-damaging exercise in the heat lowers cellular stress prior to and immediately following future exertional heat exposure

Ryan A Dunn; Hui-Ying Luk; Casey R Appell; Nigel C Jiwan; Marcos S Keefe; Jan-Joseph S Rolloque; Yasuki Sekiguchi

doi:10.1016/j.cstres.2024.05.001

Eccentric muscle-damaging exercise in the heat lowers cellular stress prior to and immediately following future exertional heat exposure

Cell Stress Chaperones. 2024 May 10;29(3):472-482. doi: 10.1016/j.cstres.2024.05.001. Online ahead of print.

Authors

Ryan A Dunn¹, Hui-Ying Luk², Casey R Appell², Nigel C Jiwan², Marcos S Keefe¹, Jan-Joseph S Rolloque¹, Yasuki Sekiguchi³

Affiliations

¹ Sports Performance Laboratory, Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, TX, USA.
² Applied Physiology Laboratory, Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, TX, USA.
³ Sports Performance Laboratory, Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, TX, USA. Electronic address: Yasuki.Sekiguchi@ttu.edu.

PMID: 38735625
DOI: 10.1016/j.cstres.2024.05.001

Abstract

Muscle-damaging exercise (e.g., downhill running [DHR]) or heat exposure bouts potentially reduce physiological and/or cellular stress during future exertional heat exposure; however, the true extent of their combined preconditioning effects is unknown. Therefore, this study investigated the effect of muscle-damaging exercise in the heat on reducing physiological and cellular stress during future exertional heat exposure. Ten healthy males (mean ± Standard Definition; age, 23 ± 3 years; body mass, 78.7 ± 11.5 kg; height, 176.9 ± 4.7 cm) completed this study. Participants were randomly assigned into two preconditioning groups: (a) DHR in the heat (ambient temperature [T_amb], 35 °C; relative humidity [RH], 40%) and (b) DHR in thermoneutral (T_amb, 20 °C; RH, 20%). Seven days following DHR, participants performed a 45-min flat run in the heat (Flat_HEAT [T_amb, 35 °C; RH, 40%]). During exercise, heart rate and rectal temperature (T_rec) were recorded at baseline and every 5-min. Peripheral blood mononuclear cells were isolated to assess heat shock protein 72 (Hsp72) concentration between conditions at baseline, immediately post-DHR, and immediately pre-Flat_HEAT and post-Flat_HEAT. Mean T_rec during Flat_HEAT between hot (38.23 ± 0.38 °C) and thermoneutral DHR (38.26 ± 0.38 °C) was not significantly different (P = 0.68), with no mean heart rate differences during Flat_HEAT between hot (172 ± 15 beats min^-1) and thermoneutral conditions (174 ± 8 beats min^-1; P = 0.58). Hsp72 concentration change from baseline to immediately pre-Flat_HEAT was significantly lower in hot (-51.4%) compared to thermoneutral (+24.2%; P = 0.025) DHR, with Hsp72 change from baseline to immediately post-Flat_HEAT also lower in hot (-52.6%) compared to thermoneutral conditions (+26.3%; P = 0.047). A bout of muscle-damaging exercise in the heat reduces cellular stress levels prior to and immediately following future exertional heat exposure.

Keywords: Downhill running; Heat shock protein 72; Heat shock response; Preconditioning; Thermotolerance.