We all know someone who can't get enough exercise: the marathon runner who jogged 26 miles in all 50 states, the neighbor who speed walks at the crack of dawn or the cyclist who zooms by every Sunday. We might say these people are addicted to physical activity. But the debate on exercise addiction has remained largely unresolved - until now, that is.
The new study, conducted at the University of Wisconsin-Madison, adds evidence that the same brain circuitry involved in other types of craving - such as for food, drugs or sex - is activated in mice that are denied access to the running wheel. The findings, say the researchers, lend support to the addictive nature of exercise in some animals.
The researchers studied changes in brain activity in two groups of rodents: typical laboratory mice and a special breed of mice selected over 29 generations for their affinity for voluntary wheel running.
"All mice run on wheels, and, therefore, have a motivation to run," says Justin Rhodes, a postdoctoral fellow at Oregon Health & Science University who completed the study while a graduate student at UW-Madison. But he adds that the specially bred mice have a genetic predisposition to run longer distances.
"They represent those few extreme individuals in the population with an intense desire or compulsion to run," he says.
To understand what drives these mice to run faster and farther than the average mouse, Rhodes and his colleagues at UW-Madison designed a study to measure changes in brain activity when both groups of mice were granted or denied access to the running wheel. For six days, they let all mice run as long as they wanted, and they recorded their distances. By and large, the high wheel ru
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Contact: Stephen Gammie
scgammie@facstaff.wisc.edu
608-262-3457
University of Wisconsin-Madison
1-Dec-2003