Adapting traditional content validation methods to fit purpose: an example with a novel video assessment and training materials in Duchenne muscular dystrophy (DMD)

Purpose The Duchenne muscular dystrophy (DMD) Video Assessment requires a caregiver to record six videos of their ambulatory child performing physical activities using a smartphone application (app). Innovative assessments that combine a performance measure, technology, and an observer require new approaches to content validation studies. This study presents a novel approach to establish the feasibility and content validity of the Video Assessment and usability of the app.