Investigation of the stress-buffering effect of physical exercise and fitness on mental and physical health outcomes in insufficiently active men: A randomized controlled trial

Objective: Exercise is seen as a possible way to manage stress, yet causal evidence regarding the stress-buffer potential of exercise is still very limited. The present study experimentally tested the stress-buffer hypothesis of exercise by examining whether participation in an aerobic exercise training program reduces the detrimental effects of stress on health. 

Methods: A total of 149 healthy and insufficiently active men were randomly assigned to a 12-week exercise training intervention, a 12-week relaxation training intervention, or a wait list control group. Health, stress, exercise levels, and physical fitness were assessed before and after the interventions. One hundred and six subjects completed all measurements and were included in the final analyses. 

Results: As the main result, covariance analyses showed that both intervention programs buffered negative effects of stress on general health and mental health; however, no significant buffer effects for physical health and physical complaints were found. Furthermore, regression analyses provided support for the assumption that the amount of exercise participants engaged in functions as a moderator of the relationship between stress and general health; physical fitness was not found to moderate the stress–health relationship. 

Conclusions: Overall, the findings present experimental support for the assumption that physical exercise buffers the effects of stress on general and mental health. Remarkably, the same effects were found for the participants of the relaxation training program. Thus, future studies need to further examine the stress-buffering effects of different exercise types as well as the effects of alternative stress-regulative interventions to determine which interventions are the most effective.