Physical Activity Moderates Effects of Stressor-Induced Rumination on Cortisol Reactivity

OBJECTIVE: Physically active individuals have lower rates of morbidity and mortality, and recent evidence indicates that physical activity may be particularly beneficial to those experiencing chronic stress. The tendency to ruminate increases and prolongs physiological stress responses, including hypothalamic-pituitary-adrenal (HPA) axis responses as indexed by cortisol reactivity to stressful experiences. We examined the association between ruminating in response to a laboratory stressor task and HPA axis reactivity and recovery and examined whether a physically active life-style moderates the associations between rumination and cortisol output trajectories. METHODS: Forty-six postmenopausal women underwent the Trier Social Stress Test, whereas salivary cortisol was repeatedly measured. Twenty-five minutes after the end of the stressor, participants reported level of rumination in response to the stress. RESULTS: Findings indicate that physical activity moderated the initial rate (B = -0.10, standard error = 0.04, p < .05) and curvature (B = -0.03, standard error = 0.01, p = .06) of the relationship between rumination and log-transformed cortisol trajectory. Among sedentary participants, those who responded to the stressor with higher levels of rumination had a more rapid initial increase in cortisol level (0.26 versus 0.21, p < .001), a later peak in cortisol reactivity (56 versus 39 minutes), and a delayed recovery from stress (curvature: -0.07 versus -0.08, p < .001) compared with those with lower levels of rumination. In active participants, cortisol trajectories were equivalent, regardless of the level of rumination. CONCLUSIONS: In sum, individuals who maintain a physically active life-style may be protected against the effects of rumination on HPA axis reactivity to and recovery from acute stress.