My son will be 9 in 3 months. His strength is still good but he seems to be getting so tired even after sleeping a good nine to ten hours. He really does not struggle with stairs and still rides a bike. I thought I should increase the meds from 21 to 24 mg but doc said no, only for strength. Should I be concerned. We try to limit him but he is very active and it's hard to do at times.....Should I be worried or is this normal?