Effects Of A Dual Challenge On Stress Hormones, Th1/th2 Cytokines, And Lymphocyte Responses In Firefighters

Abstract

Absent from the literature is an examination of the effects of a dual mental and physical challenge on stress hormones cortisol (CORT), epinephrine (EPI), norepinephrine (NE), Th1 and Th2 cytokines (IL-2, IL-6), and lymphocytes (CD8, CD56) in firefighters. PURPOSE: The purpose of this study was to examine the changes in CORT, EPI, NE, IL-2, IL-6, CD8, and CD56 in firefighters exposed to a decision-making challenge (firefighting strategies and tactics drill) while participating in moderate intensity exercise. Furthermore, relationships among these variables were examined. METHODS: Nine professional firefighters (VO2max = 36.94 ± 5.60 ml/kg/min) were asked to participate in two exercise conditions on a cycle ergometer: 1) 37 min at 60% VO2max along with 20 min of mental stress (firefighting strategies and tactics decision-making challenge (FSC)), and 2) 37 min at 60% VO2max without FSC. Stress hormones and cytokines were obtained at 0 min (baseline), after 37 minutes of exercise, and at 30 and 60 min post-exercise. Lymphocytes were analyzed at 30 min and 37 min during exercise and at 60 min post-exercise. RESULTS: A significant condition by time interaction was revealed in EPI, NE, and IL-2 In addition, significant main effects for time were observed in CORT and CD56, whereas IL-6 and CD8 demonstrated no significant changes. EPI area under the curve (AUC) was correlated with NE AUC, CORT AUC, and peak CD56 (r = 0.72, r = 0.74, and r = 0.66, respectively). NE AUC was correlated with CORT AUC and peak IL-2 (r = 0.64 and r = 0.51, respectively). CORT AUC was correlated with peak CD56 (r = 0.65). IL-6 and CD8 were not related to any of the variables assessed. CONCLUSION: Firefighters participating in a firefighting simulation task (dual challenge) responded with elevations in stress hormones that are related to elevations in IL-2 (Th1) and not related to IL-6 (Th2). These results suggest that firefighting can activate the immune system in support of a response to a possible antigen invasion. However, it is likely that if these stress hormones remained elevated or increased further, a shift from Th1 to Th2 could occur, which may suppress immune function.