What the heck happens in your body when you exercise?
What does it do in there??? I have a pretty good mental picture of resistance training, but what goes on during a cardio session? What's the difference to my body whether I sprint or do a light peddle on the stationary bike? Does working different muscles make a difference? Can your body "get used to" a certain cardio workout and become more efficient at it, thereby making it less effective for weight loss? What's the difference between the "cardio zone" and the "fat burning zone", physiologically? (I do remember that thread that mentioned laying in bed as the perfect cardio workout...)
Sorry for all the questions. I'm feel inquisitive today.