Washington ? Sure, exercise is good for your waistline, your heart, your bones – but might it also help prevent addiction to drugs or alcohol?

There are some tantalizing clues that physical activity might spur changes in the brain to do just that.

Now the government is beginning a push for hard research to prove it.

This is not about getting average people to achieve the so-called runner’s high, a feat of pretty intense athletics.

Instead, the question is just how regular physical activity of varying intensity – dancing, bicycling, swimming, tae kwan do – might affect mood, academic performance, even the very reward systems in the brain that can get hijacked by substance abuse.

What first caught the attention of National Institute on Drug Abuse chief Dr. Nora Volkow: A study found tweens and teens who reported exercising daily were half as likely to smoke as their sedentary counterparts, and 40 percent less likely to experiment with marijuana.

Volkow knows – from her own six-mile daily runs and from her scientific experiments – that the brain literally likes physical activity. Exercise seems to invigorate neurochemicals that sense and reinforce pleasure.

“In children, it’s innate,” she notes. “Children want to move.”

But the nation’s children are becoming more sedentary, and the sedentary child turns into the sedentary adult.

“Why do we lose the ability to experience pleasure from physical activity?” Volkow asked.

Last week she brought more than 100 specialists in exercise and neurobiology to a two-day conference to explore physical activity’s potential in fighting substance abuse, and announced $4 million in new research grants to help.

Drug treatment programs often include exercise, partly to keep people distracted from their cravings, but there’s been little formal research on the effects.