With a recruitment target of 80 DMD patients across 5 centres (London, Newcastle, Paris, Leiden, Nijmegen), subjects are assessed 6 monthly according to a shared protocol. Assessments include 6-minute walk distance (6MWD), North Star Ambulatory Assessment (NSAA), Performance of Upper Limb (PUL) and MyoSet (myogrip, myopinch and moviplate). Both ambulant and non-ambulant subjects undergo upper limb evaluation and respiratory function test including forced vital capacity (FVC), maximum inspiratory and expiratory pressures (MIP/MEP). A subgroup of patients performs annual whole body DEXA scan. An imaging sub-study will aim to characterize muscle (upper/lower limb) and brain MRI.