Relax, for your health
March 2, 2008
Recent research has demonstrated that exercise can be nearly as effective at combating clinical depression as modern prescription medication. Prolonged physical exertion has been linked to brain activity involving mood and motivation enhancing neurotransmitters like dopamine, serotonin, and norepinephrine.
A study published by the American College of Sports Medicine reports that just 30 minutes of moderate treadmill exercise can elevate mood and wellbeing for more than 24 hours. Other studies have returned similar results by examining clinically depressed individuals’ exercise habits. However, relying on an external force to consistently adjust the brain’s natural chemical levels, even something as physically healthy as exercise, can be dangerous.
The human body employs delicate feedback systems that make sure neurotransmitter and hormone levels remain balanced. Outside influences that increase these levels often prompt the body to reduce their own production of the chemical, which can result in a chemical dependence on that influence. Many prescription and illicit drugs can lead to this type of physical addiction, and it is possible that regular exercise may have a similar effect on some people.
In 2003 the University of Wisconsin performed a study to measure the neural activity in mice that were denied access to the running wheel they usually used. Researchers discovered that preventing these mice from exercising triggered cravings just like those exhibited by a junkie or an alcoholic.
The brain regions activated in these mice were the same as experimental mice who were not given their daily fix of morphine, alcohol, or cocaine. But what specific mechanism is regulating this addiction? Studies of overtrained athletes may provide unexpected insight into this question.
Doctors at the Kuopio Hospital studied an athlete who developed insomnia, depression, and a variety of other problems shortly after he had increased his training intensity by 200 percent. Brain imaging techniques revealed that the patient exhibited remarkably imbalanced serotonin activity in regions that are associated with emotion, higher thought processes, and sleep.
Other studies of overtrained athletes have yielded similar results. Exercise constantly activates a brain region that controls the regulation of neurotransmitters like serotonin. Chronic activation of this region is known to lead to the body’s response to down-regulate serotonin, which ultimately causes the chemical imbalance identified in overtrained athletes.
This same mechanism of action is likely involved with exercise dependence in less extreme athletes. When the activation of this brain region is more moderate, the body’s down-regulation response would be more subtle. Instead of resulting in the severe symptoms of overtraining syndrome, it may present as merely transient depression or sleeplessness.
Humans, however, are typically clever creatures. Even if the effects of an addiction are subtle, an individual would probably still modify their behavior according to the demands of their dependence. This response may not even be consciously registered.
Human addiction to exercise has previously been considered a rare psychological symptom of an obsessive personality or an eating disorder. Society’s fixation on physical beauty or the individual’s damaged self esteem are often the reasons cited for this behavior, but there is no clear consensus in the medical community.
Psychological factors may certainly have some influence, but our current understanding of neurochemistry provides a convincing hypothesis to explain this condition. However, without further research and analysis many individuals may continue to unknowingly sacrifice their mental health for physical fitness.
References
American College of Sports Medicine study of exercise and depression:
University of Wisconsin exercise addiction study:
Kupio University Hospital study on serotonin reuptake and athlete overtraining
The neurobiology of exercise and overtraining in athletes
