Could I say that all you should be doing,i s making it Fun. He is a Boy, just let Him eat a Balanced Diet Healthy Food.At this moment of Time a normal Boy is Fit. But His joints have not got the stability, to Train Hard without injury. Im workng with some young Footballers at the moment, From a big Pro Club. Problem, Trying to Hard, and having major problems with there Hips. Too much impact and hard work to young, be careful.