Interesting study on the physiology of exercise:

For the experiment, researchers at the institute gathered two types of male mice. Some were strong and aggressive; the others were less so. The alpha mice got private cages. Male mice in the wild are territorial loners. So when then the punier mice were later slipped into the same cages as the aggressive rodents, separated only by a clear partition, the big mice acted like thugs. They employed every animal intimidation technique and, during daily, five-minute periods when the partition was removed, had to be restrained from harming the smaller mice, which, in the face of such treatment, became predictably twitchy and submissive.
After two weeks of cohabitation, many of these weaker mice were nervous wrecks. When the researchers tested them in a series of stressful situations away from the cages, the mice responded with, as the scientists call it, “anxiety-like behavior.” They froze or ran for dark corners. Everything upset them. “We don’t use words like ‘depressed’ to describe the animals’ condition,” said Michael L. Lehmann, a postdoctoral fellow at the institute and lead author of the study. But in effect, those mice had responded to the repeated stress by becoming depressed.
But that was not true for a subgroup of mice that had been allowed access to running wheels and nifty, explorable tubes in their cages for several weeks before they were housed with the aggressive mice. These mice, although wisely submissive when confronted by the bullies, rallied nicely when away from them. They didn’t freeze or cling to dark spaces in unfamiliar situations. They explored. They appeared to be, Dr. Lehmann said, “stress-resistant.”

The one downer here is that the weak mice continue to submit to the bully mice even after exercising. I'd like to see them re-run the experiment, but with the weak mice exercise regimen accompanied with a peppy soundtrack:

I bet they'd stand up to the bully mice. If that fails, they could try it with the mice being coached by some kind of wise old man using inscrutable training methods.

(For those unfamiliar with the reference to Billy Zabka, see here.)