Why Does Exercise Reduce Stress? How Much Do you Need?

“It’s clear that exercise is beneficial for mental health. What’s not clear is how it works.” according to the Editor-in-Chief of the Harvard Health letter.

In one study, researchers reported that clinically depressed adults who participated in regular exercise for three months had an improvement in symptoms similar to what might have been achieved with antidepressant drugs. Other studies have found that higher levels of physical activity are associated with fewer symptoms of depression in children as well as improvement in symptoms of adults with PTSD, panic and other anxiety disorders.

Possible explanations are that vigorous exercise can increase levels of endorphins, which are known to provide a sense of well-being and increased resistance to pain. Elite marathoners may experience a feeling of euphoria referred to as the “runner’s high” and are often so insensitive to pain that they continue to run on broken bones that would normally bring them to an immediate halt. However, the old adage “no pain, no gain” no longer seems to be valid since many stress reduction rewards can be achieved by walking for 20-30 minutes several times a week or other much milder physical activities that promote a sense of well being. The support provided by others in group exercise activities as well as an improved sense of self–esteem associated with physical activity can also have powerful stress reduction effects.

Some people who are depressed or anxious may not have any desire to exercise but should be encouraged to do as much as they can, even if it’s just a few minutes at a time. The reason is that this often leads them to increase their activities bit by bit as they experience more benefits. According to the Harvard Mental Health Letter, “You don’t have to have a program that includes 45 minutes of sweating and grunting and moaning . . . . A 10-minute walk is as good a place to start as anything else.”

In animal studies, rats who were allowed to exercise as much as they wanted to on a free running wheel showed less severe and fewer “fight or flight” responses to a painful stressor compared to litter mates in similar cages with a fixed wheel. The exercise group had lower levels of stress related hormones and reduced sympathetic nervous system responses that may explain these findings.As will be seen in a future Stress Bulletin, regular exercise also improves cardiovascular and immune system function.

Paul J. Rosch, M.D., F.A.C.P.
Chairman of the Board, The American Institute of Stress

References
Harvard Mental Health Letter, December 2005, Bartholomew JB, et al. Effects of Acute Exercise on Mood and Well-Being in Patients with Major Depressive Disorder. Med Sci Sports Exerc. 2005;37:2032-2037. Fleshner M. Physical Activity Reduces the Negative Effects of Stress on Behavior, Neural, Endocrine and Immune Responses: Med Sci Sports Exerc. May, 2005; 37(5),. Supplement:S134 Greenwood BN, Kennedy S., Smith TP, et al. Voluntary freewheel running selectively decreases the peripheral sympathetic stress response by modulating activity of the central sympathetic circuit. Neuroscience 2003; 120:269-281. Health And Stress Newsletter #1, #12, 1994 and #4, 2005.