Steve Sailer has a post about a New York Times article that notes violent criminals tend to be fit. Duh. Do you think someone will attack you unless he possesses force majeur?
A Libertarian Party presidential candidate once had the idea that criminals should spend the first month in jail in bed. That way, they would be less physically fit and easier to control. A riot by 90 lb. weaklings is not to be greatly feared.
There should be no physical training equipment in prisons. The diet and exercise program should be tailored to make sure the lads (and it is mostly lads) come out unfit.
Eric Nagourney, the author cites a Dr. Walker that “Those who are fit may have personalities that are more likely to make them violent.” Even if we can't expunge the propensity, I would much rather be threatened with mugging by someone who is wheezing from the effort.