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

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 [Tamb], 35 °C; relative humidity [RH], 40%) and (b) DHR in thermoneutral (Tamb, 20 °C; RH, 20%). Seven days following DHR, participants performed a 45-min flat run in the heat (FlatHEAT [Tamb, 35 °C; RH, 40%]). During exercise, heart rate and rectal temperature (Trec) 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-FlatHEAT and post-FlatHEAT. Mean Trec during FlatHEAT 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 FlatHEAT 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-FlatHEAT was significantly lower in hot (−51.4%) compared to thermoneutral (+24.2%; P = 0.025) DHR, with Hsp72 change from baseline to immediately post-FlatHEAT 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.

Description

© 2024 cc-by-nc-nd

Keywords

Downhill running, Heat shock protein 72, Heat shock response, Preconditioning, Thermotolerance

Citation

Dunn, R.A., Luk, H.-Y., Appell, C.R., Jiwan, N.C., Keefe, M.S., Rolloque, J.-J.S., & Sekiguchi, Y.. 2024. Eccentric muscle-damaging exercise in the heat lowers cellular stress prior to and immediately following future exertional heat exposure. Cell Stress and Chaperones, 29(3). https://doi.org/10.1016/j.cstres.2024.05.001

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