 The goal of this project is to assess the safety and feasibility of a home based mild to moderate-intensity strengthening exercise program in boys with Duchenne muscular dystrophy DMD. Evidence from milder forms of muscular dystrophy and mouse models of DMD suggests that strengthening exercise may be beneficial for these children, but this area has not been adequately explored using human subjects. The results of this study should provide information to assist in the development of scientifically based recommendations concerning optimal exercise parameters for patients with DMD. 