Exercise and sports activity are beneficial both physically and psychologically but excessive exercise may have adverse
physiological and psychological effects. There are methodological issues in the definition, diagnosis and etiology of exercise addiction.
Several questionnaires and diagnostic tools have been developed and validated and they show high validity and reliability. Exercise addiction
has been suggested as having an obsessive-compulsive dimension as well as rewarding aspects that may include it among the behavioral
addictions. Biological studies show that in rodents, exercise such as wheel running activates the dopamine reward system and
thus contributing to stress reduction. Further evidence suggests that running is associated with endorphins and cannabinoids thus explaining
the “runners high” or euphoric feelings that may lead to exercise addiction. Genetic studies suggest that genes which control preference
for drugs also control the preference for naturally rewarding behaviors such as exercise. Psychological studies also explain exercise
addiction in terms of reward, habituation, social support, stress-relief, avoidance of withdrawal and reduction of anxiety. It has been suggested
that exercise addiction is a part of a continuum of sportive activity that develops in stages from the recreational exercise to at-risk
exercise, problematic exercise and finally into exercise addiction. Assessment and treatment should take into account the various stages
of exercise addiction development, its comorbidity with other psychiatric disorders such as eating disorders or substance use and alcohol
disorders. Treatment approaches for exercise addiction are based on the cognitive-behavioral approach but little is known about their effectiveness.
A single-case study shows promise of pharmacological treatment for exercise addiction and further studies are required. This
review summarizes diagnostic and phenomenology of exercise addiction with emphasis on physiological and neuro-pharmacological
mechanisms responsible for its rewarding and addictive properties.