Do fast workouts really work?

... a part of the all-intensity programs popularized by CrossFit-style gyms and the bestselling at-home DVD workouts like P90X and Insanity. But skepticism abounds, as some doctors say the idea sounds too good to be true. The pace might be too much. ...

http://www.macon.com/2014/01/13/2876736/do-fast-workouts-really-work.html#storylink=rss