Journal Article
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
European Journal of Applied Physiology · Vol. 125, Issue 11 · pp. 3209-3222 · 2025
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, VO 2 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 (T c ), mean body temperature (T b ), minute ventilation (V E ), and oxygen consumption (VO 2 ) 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, T c , T b , V E or VO 2 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, T c or T b 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.