I'm glad to see that he's growing healthy; the parents must be spending a fortune for food bills. The one article I was reading said that people with that disorder (myostatin-related muscle hypertrophy) often end up with brain damage since their body requires so much nourishment that the brain often becomes malnourished, for lack of a better word, since their body is in a constant state of starvation.
Given the modern protein and vitamin supplements though, it looks like the parents are raising him correctly and encouraging heavy activity from the get-go along with gymnastic trainers, which means that he will have an outlet to use his amazing gift. Given that he's already so strong, if his growth patterns continue, he may grow up to be the best athlete of his time. The base condition typically has 40% more muscle mass than a standard person, and the muscles themselves appear to be stronger and more dense.