Instead of testing actual runners, the scientists tested rats. The 84 rodents were divided into two types of cages, ones with wheels and ones without. Over a week, the rats that had access to the wheel naturally increased how much they ran. On day nine, about half the group was only given access to food for one hour per day, while the others continued to have food all the time. The food-restricted rats began exercising even more, and also started to lose weight. All the rats were then given the drug Naloxone, a chemical compound that is often used to help drug abusers recover from addiction and immediately causes withdrawal symptoms. The biggest "gym rats" showed the greatest degree of withdrawal symptoms, while rats that couldn't exercise displayed fewer withdrawal symptoms.
The scientists concluded that the release of chemicals during exercise mimics the sensations morphine and heroin users feel. If a runner's high is similar to a high brought on by drugs, the researchers propose that exercise could be used as a replacement "drug" to help drug addicts recover. What do you think?