Photo: Exercise Can Be Like Heroin, "Gym Rats" Show



Hardcore runners who can't bear to skip a workout may have an addiction similar to heroin addiction, according to a new study of rats (above, a rat on a wheel in Maryland).

When highly active rats were given a chemical that helps drug abusers recover, the animals exhibited classic addiction withdrawal symptoms, according to an August 2009 study.

Photograph by Joseph H. Bailey


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