Duchenne muscular dystrophy (DMD) is a fatal disease caused by dystrophin deficiency.Dystrophy symptom is seen in the canine but not murine DMD models.To test gene therapy efficacy, we developed a novel protocol to transfer adeno-associated virus micro-dystrophin (AAV μdys) vector into the extensor carpi ulnaris muscle (ECU) of dystrophy dogs.We also developed an apparatus to measure the ECU force.Robust and sustained micro-dystrophin expression was achieved following direct AAV μdys injection.