Mental Health
The relationship between exercise and mental health is well established

Click on images below for articles from major health advocates.
"The importance of exercise is not adequately understood or appreciated by patients and mental health professionals alike. 
"Aerobic exercises, including jogging, swimming, cycling, walking, gardening, and dancing, have been proved to reduce anxiety and depression."

"There's good epidemiological data to suggest that active people are less depressed than inactive people. And people who were active and stopped tend to be more depressed than those who maintain or initiate an exercise program,says James Blumenthal, PhD, a clinical psychologist at Duke University.
Suzanne Yokoyama, M.D., 
Kaiser Permanente
on exercise and health
Benefits of exercise for managing stress
Dr Alan Cohen says that when people get depressed or anxious, they often feel they're not in control of their lives.
"Exercise gives them back control of their bodies and this is often the first step to feeling in control of other events," he says.

The National Health Service, U.K. on benefits of exercise for mental health