Magnetic Resonance Imaging and Biomarkers for Muscular Dystrophy

Inclusion Criteria for boys with DMD: 1\. Ambulatory and non-ambulatory males (ages 5-30 at baseline testing) previously diagnosed with DMD based on: * clinical features with onset of symptoms before age five * elevated serum creatine kinase level or * absence of dystrophin expression, as determined by immunostain or western blot (\<2%) and/or DNA confirmation of a dystrophin mutation \*Subjects will not be excluded based on corticosteroid treatment or other clinical trials Inclusion Criteria for adults with Becker MD: 1. Ambulatory males (ages 18-62) without disease or injury to the lower extremities 2. Specific recruitment of a subset of individuals with deletion mutations in the dystrophin gene involving either exon 51 or exon 45. Inclusion Criteria for age matched controls for Becker MD subjects: 1\. Ambulatory males (ages 18-62) without disease or injury to the lower and/or upper extremities will be eligible to participate in this study Exclusion Criteria: 1. Males with a contraindication to an MR examination 2. Males with unstable medical problems 3. Males who are not able to cooperate during testing 4. Males with a secondary condition that may impact muscle metabolism, muscle function or functional ability (i.e. cerebral palsy, endocrine disorders, mitochondrial disease) 5. Daytime ventilation 6. Implantable Cardioverter Defibrillator- (ICD) or pace maker 7. Healthy boys/men who participate in competitive sports specific training in excess of 8 hours per week