We are talking PERMANENT scarring, etc., to the heart, a weakened immune system, you name it.

Read it:

http://fitness.mercola.com/sites/fitness/archive/2012/06/01/long-cardio-workout-dangers.aspx

Here is the link:

http://www.suntimes.com/lifestyles/splash/12897596-418/fitness-guru-jim-karas-tackles-a-weighty-topic.html#.T8zgN14R0aQ.facebook