Researchers at Tufts University gave naloxone, a medicine for heroin overdose that produces immediate withdrawal symptoms, to rats that ran in exercise wheels. The rats showed withdrawal symptoms like those seen in narcotics addicts. And the rodents that ran the hardest had the most severe withdrawal symptoms.
The scientists found that the rats showed similar behaviors to rats addicted to drugs. "Exercise, like drugs of abuse, leads to the release of neurotransmitters such as endorphins and dopamine, which are involved with a sense of reward," noted lead author Robin Kanarek, PhD.
But don't let a potential addiction be another excuse to not run. "As with food intake and other parts of life, moderation seems to be the key. Exercise, as long as it doesn't interfere with other aspects of one's life, is a good thing with respect to both physical and mental health," said Kanarek.
So scientists got a bunch of rats addicted to running. That's just not that impressive. Let me know when the rats are addicted to their Garmins. (GARMIN: Praise Be Thy Name!).