Depression

A melancholy mood; a feeling of hopelessness or an attitude of dejection. Depression varies from mild forms, which most people experience, to very severe clinical forms that require expert medical treatment.
Although depression can affect the motivation to exercise, it is generally agreed that aerobic activity can protect against and relieve depression.
Aerobic exercise sustained for at least 30 minutes, five times a week, can have remarkable anti-depressant effects.
The reason is unclear, but may be linked to the production of endorphins during exercise, or increased self-esteem and control.