High-Intensity Exercisers Must Know Their Limits

Web entrepreneur Matt Lombardi said he just wanted to get into shape -- but it took only one session of the popular P90X workout series to send the 29-year-old to the hospital with rhabdomyolysis, a relatively rare condition he said his doctors told him occurs when muscle tissue breaks down to such an extent that toxins released into the blood ... (more)

http://abcnews.go.com/Health/p90x-high-intensity-workouts-carry-risks-rewards/story?id=19896015