Exercise Improves Mood

As noted in several of our Newsletters, regular physical exercise has been shown to reduce depression and anxiety and to provide other stress reduction rewards that can improve cardiovascular and immune system function. In addition, aerobic exercise increases blood flow to the heart and causes dilation of small blood vessels that allows them to deliver more oxygen to muscle and other tissues. Because of its ability to prevent heart attacks exercise is the cornerstone of cardiac rehab programs and has been shown to lower blood pressure in some hypertensive patients.

Exercise can also improve immune system function. Teen-age girls who exercised regularly had fewer colds and other infections than their more sedentary classmates. Aerobic exercise also bolsters immune system defenses in HIV patients. Weight lifting and other anaerobic exercises improve muscle tone and strength and both types of exercise can increase bone density that helps to prevent osteoporosis. Along with a proper diet, exercise can reduce body fat and weight.

Some of these benefits may be due to the ability of exercise to prevent stress-induced suppression of the immune system by its effects on the sympathetic nervous system. In one study, rats were housed in a cage with a mobile running wheel and were allowedto run whenever they wanted. Littermates were housed under identical circumstances but with a running wheel that did not move. After four weeks, both groups were exposed to a painful stressor and an antigen was administered to determine immune system responses. Periodic blood tests showed that the production of protective immune system components was much higher in the exercise group of rats. This group also had a corresponding reduction in stress hormone levels that could explain these effects. In addition, exercise was associated with less severe and fewer “fight or flight” sympathetic nervous system responses to a painful stressor.

References: Fleshner, M.
Physical Activity and Stress Resistance: Sympathetic Nervous System Adaptations Prevent Stress-Induced Immunosuppression. Exercise & Sport Sciences Reviews. 33(3):120-126, July 2005. Kennedy S, Smith L, Taro P, Fleshner M. Resting Cellular and Physiological Effects of Freewheel Running. Med Sci Sports Exerc 2005: 37:79-83. 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 #4,#5 2005, #7 2000, #5 1999.