Establishing Walking-related Digital Biomarkers in Rare Childhood Onset Progressive Neuromuscular Disorders

Inclusion Criteria: * Genetic confirmation of disease (DMD, SMA) or healthy control * Able to walk independently at least 25 meters * Ongoing corticosteroids therapy or initiation of corticosteroid therapy in the previous 3 months for DMD * Stable dose of FDA approved SMN up-regulator therapy or in an open-label extension phase of a study treatment for at least 6 months for SMA or gene replacement at enrollment for SMA or DMD participants. Exclusion Criteria: * Use foot orthoses or assistive devices for community ambulation or a mobility device for community navigation * Use investigational medications intended for treatment of NMD within 30 days * Prior to study entry had an injury or surgery that would impact gait within the previous 3 months