Does aerobic capacity protect against stress? Insights from two stress-induction paradigms

Introduction: Prior evidence suggests that individuals with higher fitness exhibit attenuated endocrine and autonomic responses to acute stress. However, it remains unclear whether this stress-buffering effect depends on the type of stressor. This study examined whether aerobic capacity modulates psychophysiological responses to two stress induction paradigms (Trier Social Stress Tests, TSST; Maastricht Acute Stress Test, MAST). We hypothesized that fitter participants show lower stress reactivity, with stronger attenuation expected for the MAST, which includes a physical stress component. Methods: Healthy participants (n = 59; 28 women; age: 27.1 ± 5.5 yrs) completed the TSST and MAST on separate days under standardized conditions. We assessed self-reported stress, salivary hormones (cortisol, cortisone, DHEAS), and autonomic cardiac regulation (heart rate, RMSSD). Aerobic fitness was determined via graded exercise testing (VO2peak: 50.4 ± 8.6 ml/kg/min). We used multilevel regression models to examine the associations between VO2peak and stress responses. Results: Higher VO2peak was significantly associated with lower heart rate across both stress induction paradigms (b = 0.99 bpm, p = 0.002). For other outcomes, no significant association with VO2peak was found. The associations did not differ between TSST and MAST. Discussion: Aerobic fitness was linked to lower heart rate during the experimental sessions, indicating a modest cardiovascular advantage under acute stress. Contrary to our hypothesis, this effect did not differ between the two stress paradigms, suggesting that the influence of fitness was not specific to the type of stressor. Aerobic capacity, therefore, seems to reduce cardiovascular load during stressful situations in a general manner.