I'm studying cardio...

I was never a HUGE fan of cardio, but after studying it... it seems extremely useful. Unfortunately, cardio 3x a week means less time to of good rest for muscles. Thinking realistically, when will you run in a real-life situation? Either you will be running away from something in a strange panic, or you will be running to something because you are in a rush. You don't jog in real life. In both cases, I would expect that a person would be moving fast, maybe 60%-90% of max effort. So if you want to be practical, do interval training for something to get your body used to workin'.

But if you just want an efficient heart, I guess jogging 3x a week is Ok. What am I talking about?