Immune Response in Women during Exercise in the Heat: A Spotlight on Oral Contraception

This study compared the immune and stress response of oral contraceptive users (WomenOC; n = 9) to normally-menstruating women (WomenNM; n = 9) at rest and during exercise in temperate (TEMP; 22°C) and hot (HEAT; 35°C) conditions. Participants performed a 3-stage cycling trial in each condition at 90% (Stage 1; 30 min), 135% (Stage 2; 15 min), and 180% (Stage 3; 7.5 min) of lactate threshold 1. C-reactive protein (CRP) and immune cell counts were measured at rest, and serum cytokines (IL-1β, IL-1RA, IL-6, IL-8, IL-10, and TNF-α) and salivary cortisol were evaluated before and after exercise in both the TEMP and HEAT conditions. There were no differences in resting immune cell counts between groups, nor any differences in cortisol or any of the pro- or anti-inflammatory cytokines measured at rest or after completion of the exercise trials (p > 0.05). However, a trend for a higher resting CRP concentration was observed in WomenOC relative to WomenNM (1.102 ± 1.182 and 0.326 ± 0.228, respectively, p = 0.07). The results obtained in the current study indicate similar immunoendocrine function in WomenOC and WomenNM both at rest and after exercise in temperate and hot environments.