The physical benefits of exercise — improving physical condition and fighting disease — have long been established, and physicians always encourage staying physically active.
Exercise is also considered vital for maintaining mental fitness, and it can reduce stress. Studies show that it is very effective at reducing fatigue, improving alertness and concentration, and at enhancing overall cognitive function. This can be especially helpful when stress has depleted your energy or ability to concentrate.
When stress affects the brain, with its many nerve connections, the rest of the body feels the impact as well. Or, if your body feels better, so does your mind. Exercise and other physical activity produce endorphins — chemicals in the brain that act as natural painkillers — and also improve the ability to sleep, which in turn reduces stress.
Scientists have found that regular participation in aerobic exercise has been shown to decrease overall levels of tension, elevate and stabilize mood, improve sleep, and improve self-esteem. About five minutes of aerobic exercise can begin to stimulate anti-anxiety effects.
Stress and anxiety are a normal part of life, but anxiety disorders , which affect 40 million adults, are the most common psychiatric illnesses in the U.S. The benefits of exercise may well extend beyond stress relief to improving anxiety and related disorders.
Psychologists studying how exercise relieves anxiety and depression suggest that a 10-minute walk may be just as good as a 45-minute workout. Some studies show that exercise can work quickly to elevate depressed mood in many people. Although the effects may be temporary, they demonstrate that a brisk walk or other simple activity can deliver several hours of relief, similar to taking an aspirin for a headache.
Science has also provided some evidence that physically active people have lower rates of anxiety and depression than sedentary people. Exercise may improve mental health by helping the brain cope better with stress. In one study, researchers found that those who got regular vigorous exercise were 25 percent less likely to develop depression or an anxiety disorder over the next five years.
According to some studies, regular exercise works as well as medication  for some people to reduce symptoms of anxiety and depression, and the effects can be long lasting. One vigorous exercise session can help alleviate symptoms for hours, and a regular schedule may significantly reduce them over time.
Although exercise has a positive effect for most people, some recent studies show that for some, exercise may not have a positive effect on anxiety or depression  or may not make a strong impact on long-term mental health.
Like all forms of therapy, the effect can vary: Some people may respond positively, others may find it doesn’t improve their mood much, and some may experience only a modest short-term benefit. Nonetheless, researchers say that the beneficial effects of exercise on physical health are not in dispute, and people should be encouraged to stay physically active.
Read all about it: Exercise for Mood and Anxiety, Proven Strategies for Overcoming Depression and Enhancing Well-Being,  by Michael W. Otto, PhD, and Jasper A.J. Smits, PhD (Oxford University Press, 2011)
The most recent federal guidelines  for adults recommend at least 2½ hours of moderate-intensity physical activity (e.g. brisk walking) each week, 1¼ hours of a vigorous-intensity activity (such as jogging or swimming laps), or a combination of the two.
If you have an exercise program already, keep up the good work. If not, here are tips to get you started.