Why Exercise Resolutions Are Hard to Keep

The fact that scores of people resolve to start an exercise regimen in the new year and then slide back into their old couch potato ways is common knowledge. But why is this so? Researchers in France, who published their findings in the journal Biological Psychiatry, contend that a protein called the CB1 cannabinoid receptor in a region of the brain associated with motivation and reward systems controls whether or not a person will voluntarily engage in physical activity. The endocannabinoid system is involved in physiological processes including appetite, pain, mood, memory, and – you guessed it! -- the psychoactive effects of marijuana.  

A release from the research institution, called INSERM, quotes Francis Chaouloff as saying, "The inability to experience pleasure during physical activity, which is often quoted as one explanation why people partially or completely drop out of physical exercise programs, is a clear sign that the biology of the nervous system is involved."

Based on the results of this study and earlier work, the team suggests that at the beginning and for the duration of physical exercise, the CB1 receptor is constantly simulated by the endocannabinoids, lipid molecules that naturally activate this receptor in response to pleasant stimuli (rewards) and unpleasant stimuli (stress). The research shows that physical exercise can be added to the array of natural rewards regulated by the endocannabinoid system. "If confirmed, this motivational hypothesis would imply that the role played by the CB1 receptor has more to do with 'staying power' in the exercise than with actual physical performance levels", the researchers explain.

The research opens up new avenues of research into the mediators of pleasure – and even addiction – associated with regular physical exercise. "After endorphins, we now need to consider endocannabinoids as another potential mediator of the positive effects that physical exercise has on our mood," the researchers conclude. 


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