Prior SARS-CoV-2 infection does not increase heat stress during one hour of exercise in a hot and moderately humid environment

Emerson P. Heckler; Nathan J. Conrad; Karissa N. Fryar; Rachael S. Badeau; Rachel M. Kowis; Ben J. Lee; Trevor L. Gillum; Matthew R. Kuennen

doi:10.1007/s00421-025-05812-3

Prior SARS-CoV-2 infection does not increase heat stress during one hour of exercise in a hot and moderately humid environment

Emerson P. Heckler
, Nathan J. Conrad
, Karissa N. Fryar
, Rachael S. Badeau
, Rachel M. Kowis
, Ben J. Lee
, Trevor L. Gillum
, Matthew R. Kuennen

Research output: Contribution to journal › Article › peer-review

1 Citation (Scopus)

Abstract

Purpose: Prior viral infection has been suggested to increase exertional heatstroke (EHS) risk. This study examined physiological and immune responses in persons with prior clinical diagnosis of SARS-CoV-2 infection, who were challenged with 1 h of cycling exercise in hot, moderately humid ambient conditions. Methods: Fourteen men and six women (age: 21 ± 1 years, stature: 1.7 ± 0.1 m, mass: 70.7 ± 2.6 kg, VO2 max: 47 ± 1 mL kg lbm−1 min−1) completed 1 h of cycling exercise at an intensity that elicited 7.0 W/kg of metabolic heat production in an environmental chamber (35 °C/35% RH). Ten participants had been previously diagnosed with SARS-CoV-2 and ten participants served as CONTROL. Physiological parameters including heart rate (HR), esophageal temperature (Tc), mean body temperature (Tb), minute ventilation (VE), and oxygen consumption (VO2) were measured throughout exercise. Blood samples collected at Pre, Post, 1 h-Post, and 3 h-Post exercise were assayed for immune markers including Interleukin 1 receptor antagonist (IL-1RA) and interferon gamma (IFN-γ). Results: As compared to CONTROL, prior SARS-CoV-2 infection did not cause greater elevations in HR, Tc, Tb, VE or VO2 during 1 h of cycling exercise [all p > 0.05]. The increase in IL-1RA at 1 h-Post exercise in SARS-CoV-2 (195 ± 104%, p = 0.012) was greater than the increase in CONTROL (44 ± 18%, p = 0.002). IFN-y was elevated at 1 h-Post exercise in SARS-CoV-2 (105 ± 50%, p = 0.021) but did not increase following exercise in CONTROL (p > 0.05). Conclusions: Prior SARS-CoV-2 infection did not alter metabolic responses or increase the rate of rise in HR, Tc or Tb during matched workload cycling exercise under hot, moderately humid ambient conditions. IL-1RA is an anti-inflammatory cytokine and IFN-y exhibits direct anti-viral activity, suggesting that immunocompetence was maintained during exertional heat stress.

Original language	English
Pages (from-to)	3209-3222
Number of pages	14
Journal	European Journal of Applied Physiology
Volume	125
Issue number	11
Early online date	26 May 2025
DOIs	https://doi.org/10.1007/s00421-025-05812-3
Publication status	Published - 1 Nov 2025

Bibliographical note

© The Author(s) 2025
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not
permitted by statutory regulation or exceeds the permitted use, you will
need to obtain permission directly from the copyright holder.

Funding

Open access funding provided by the Carolinas Consortium. Support for this work was provided by the Department of Health & Human Performance within the Congdon School of Health Sciences. We wish to thank the participants for their effort and dedication during the experiments. We would also like to thank the Department of Physical Therapy (Congdon School of Health Sciences) for the use of shared lab space and LJK for his lifetime of guidance and support.

Funders
Carolinas Consortium
High Point University

Keywords

Exercise
Heat stroke
Immune
Inflammation
SARS-CoV-2
Viral infection

Access to Document

10.1007/s00421-025-05812-3Licence: CC BY

Lee2025VoRFinal published version, 2.51 MBLicence: CC BY

Cite this

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title = "Prior SARS-CoV-2 infection does not increase heat stress during one hour of exercise in a hot and moderately humid environment",

abstract = "Purpose: Prior viral infection has been suggested to increase exertional heatstroke (EHS) risk. This study examined physiological and immune responses in persons with prior clinical diagnosis of SARS-CoV-2 infection, who were challenged with 1 h of cycling exercise in hot, moderately humid ambient conditions. Methods: Fourteen men and six women (age: 21 ± 1 years, stature: 1.7 ± 0.1 m, mass: 70.7 ± 2.6 kg, VO2 max: 47 ± 1 mL kg lbm−1 min−1) completed 1 h of cycling exercise at an intensity that elicited 7.0 W/kg of metabolic heat production in an environmental chamber (35 °C/35\% RH). Ten participants had been previously diagnosed with SARS-CoV-2 and ten participants served as CONTROL. Physiological parameters including heart rate (HR), esophageal temperature (Tc), mean body temperature (Tb), minute ventilation (VE), and oxygen consumption (VO2) were measured throughout exercise. Blood samples collected at Pre, Post, 1 h-Post, and 3 h-Post exercise were assayed for immune markers including Interleukin 1 receptor antagonist (IL-1RA) and interferon gamma (IFN-γ). Results: As compared to CONTROL, prior SARS-CoV-2 infection did not cause greater elevations in HR, Tc, Tb, VE or VO2 during 1 h of cycling exercise [all p > 0.05]. The increase in IL-1RA at 1 h-Post exercise in SARS-CoV-2 (195 ± 104\%, p = 0.012) was greater than the increase in CONTROL (44 ± 18\%, p = 0.002). IFN-y was elevated at 1 h-Post exercise in SARS-CoV-2 (105 ± 50\%, p = 0.021) but did not increase following exercise in CONTROL (p > 0.05). Conclusions: Prior SARS-CoV-2 infection did not alter metabolic responses or increase the rate of rise in HR, Tc or Tb during matched workload cycling exercise under hot, moderately humid ambient conditions. IL-1RA is an anti-inflammatory cytokine and IFN-y exhibits direct anti-viral activity, suggesting that immunocompetence was maintained during exertional heat stress.",

keywords = "Exercise, Heat stroke, Immune, Inflammation, SARS-CoV-2, Viral infection",

author = "Heckler, \{Emerson P.\} and Conrad, \{Nathan J.\} and Fryar, \{Karissa N.\} and Badeau, \{Rachael S.\} and Kowis, \{Rachel M.\} and Lee, \{Ben J.\} and Gillum, \{Trevor L.\} and Kuennen, \{Matthew R.\}",

note = "{\textcopyright} The Author(s) 2025 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article{\textquoteright}s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article{\textquoteright}s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.",

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doi = "10.1007/s00421-025-05812-3",

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TY - JOUR

T1 - Prior SARS-CoV-2 infection does not increase heat stress during one hour of exercise in a hot and moderately humid environment

AU - Heckler, Emerson P.

AU - Conrad, Nathan J.

AU - Fryar, Karissa N.

AU - Badeau, Rachael S.

AU - Kowis, Rachel M.

AU - Lee, Ben J.

AU - Gillum, Trevor L.

AU - Kuennen, Matthew R.

N1 - © The Author(s) 2025 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

PY - 2025/11/1

Y1 - 2025/11/1

N2 - Purpose: Prior viral infection has been suggested to increase exertional heatstroke (EHS) risk. This study examined physiological and immune responses in persons with prior clinical diagnosis of SARS-CoV-2 infection, who were challenged with 1 h of cycling exercise in hot, moderately humid ambient conditions. Methods: Fourteen men and six women (age: 21 ± 1 years, stature: 1.7 ± 0.1 m, mass: 70.7 ± 2.6 kg, VO2 max: 47 ± 1 mL kg lbm−1 min−1) completed 1 h of cycling exercise at an intensity that elicited 7.0 W/kg of metabolic heat production in an environmental chamber (35 °C/35% RH). Ten participants had been previously diagnosed with SARS-CoV-2 and ten participants served as CONTROL. Physiological parameters including heart rate (HR), esophageal temperature (Tc), mean body temperature (Tb), minute ventilation (VE), and oxygen consumption (VO2) were measured throughout exercise. Blood samples collected at Pre, Post, 1 h-Post, and 3 h-Post exercise were assayed for immune markers including Interleukin 1 receptor antagonist (IL-1RA) and interferon gamma (IFN-γ). Results: As compared to CONTROL, prior SARS-CoV-2 infection did not cause greater elevations in HR, Tc, Tb, VE or VO2 during 1 h of cycling exercise [all p > 0.05]. The increase in IL-1RA at 1 h-Post exercise in SARS-CoV-2 (195 ± 104%, p = 0.012) was greater than the increase in CONTROL (44 ± 18%, p = 0.002). IFN-y was elevated at 1 h-Post exercise in SARS-CoV-2 (105 ± 50%, p = 0.021) but did not increase following exercise in CONTROL (p > 0.05). Conclusions: Prior SARS-CoV-2 infection did not alter metabolic responses or increase the rate of rise in HR, Tc or Tb during matched workload cycling exercise under hot, moderately humid ambient conditions. IL-1RA is an anti-inflammatory cytokine and IFN-y exhibits direct anti-viral activity, suggesting that immunocompetence was maintained during exertional heat stress.

AB - Purpose: Prior viral infection has been suggested to increase exertional heatstroke (EHS) risk. This study examined physiological and immune responses in persons with prior clinical diagnosis of SARS-CoV-2 infection, who were challenged with 1 h of cycling exercise in hot, moderately humid ambient conditions. Methods: Fourteen men and six women (age: 21 ± 1 years, stature: 1.7 ± 0.1 m, mass: 70.7 ± 2.6 kg, VO2 max: 47 ± 1 mL kg lbm−1 min−1) completed 1 h of cycling exercise at an intensity that elicited 7.0 W/kg of metabolic heat production in an environmental chamber (35 °C/35% RH). Ten participants had been previously diagnosed with SARS-CoV-2 and ten participants served as CONTROL. Physiological parameters including heart rate (HR), esophageal temperature (Tc), mean body temperature (Tb), minute ventilation (VE), and oxygen consumption (VO2) were measured throughout exercise. Blood samples collected at Pre, Post, 1 h-Post, and 3 h-Post exercise were assayed for immune markers including Interleukin 1 receptor antagonist (IL-1RA) and interferon gamma (IFN-γ). Results: As compared to CONTROL, prior SARS-CoV-2 infection did not cause greater elevations in HR, Tc, Tb, VE or VO2 during 1 h of cycling exercise [all p > 0.05]. The increase in IL-1RA at 1 h-Post exercise in SARS-CoV-2 (195 ± 104%, p = 0.012) was greater than the increase in CONTROL (44 ± 18%, p = 0.002). IFN-y was elevated at 1 h-Post exercise in SARS-CoV-2 (105 ± 50%, p = 0.021) but did not increase following exercise in CONTROL (p > 0.05). Conclusions: Prior SARS-CoV-2 infection did not alter metabolic responses or increase the rate of rise in HR, Tc or Tb during matched workload cycling exercise under hot, moderately humid ambient conditions. IL-1RA is an anti-inflammatory cytokine and IFN-y exhibits direct anti-viral activity, suggesting that immunocompetence was maintained during exertional heat stress.

KW - Exercise

KW - Heat stroke

KW - Immune

KW - Inflammation

KW - SARS-CoV-2

KW - Viral infection

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U2 - 10.1007/s00421-025-05812-3

DO - 10.1007/s00421-025-05812-3

M3 - Article

SN - 1439-6319

VL - 125

SP - 3209

EP - 3222

JO - European Journal of Applied Physiology

JF - European Journal of Applied Physiology

IS - 11

ER -

Prior SARS-CoV-2 infection does not increase heat stress during one hour of exercise in a hot and moderately humid environment

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Keywords

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