I was thinking about cardio the other day and it got me thinking...how does a heart get stronger?
The heart is a muscle. We know that our other muscles tear (with use) and then the scar tissue that is built during recovery increase muscle size and thus strength. SO when cardio excercise is performed does that mean that your heart is tearing in some fashion?
And would taking extra protein on cardio days help improve your results as it does when you work your other muscle groups?