endurance

What I don't understand is how everyone says if you are trying to build muscle you shouldn't be doing more than 2-3 cardio workouts a week, otherwise you start to lose muscle. Looking at AFL players, it doesn't quite make sense. They do lots of gym, and a hell of a lot of running, and somehow...

I was wondering if my 11 year old son could get private coaching particularly for strength and conditioning we live in the North near Churchlands. He has difficulty running out a game and tackling or breaking a tackle. These are all strength and conditioning related so I'd like to work with...