Had a quick question regarding why its best to do cardio first thing in the morning on an empty stomach. I constantly have read on this board that its the best thing to do (and I myself do it as well--low impact )...Im not questioning that its the best just wondering what makes it so good. My idea is moring cardio on an empty stomach is the best because when you wake up your glycogen stores are depleted therefore your body goes straight to fat to burn for energy?

Continuing w/ this I've heard/read from other people that it takes 20minutes for your body to start burning calories when doing cardio...is this simply a myth or is it factual if ones glycogen stores were "full" thats how long it would take to deplete them hence rendering morning cardio "the best time" to do cardio?

My last question is why wouldnt it be ideal for a person to do cardio after a workout. A persons glycogen stores are depleted following a workout (someone correct me if im wrong in any of my statements please) which would make it an ideal time? but then i take into consideration your muscles are in a catabolic state following a workout therefore placing further strain on them via cardio (even low impact) could result in further muscular depletion?

Sorry for the long post guys but thank you for the help! just trying to get my thoughts straight on this