Spinal muscular atrophy type III, (SMAIII) is a recessively inherited disease in the lower motor neuron in the anterior horn of spinal cord leading to to progressive muscle weakness and atrophy. Currently there is no effective treatment available for SMA. We have previously shown that patients with muscular dystrophies improve oxidative capacity (VO2max), muscle strength and daily function by aerobic conditioning. Patients with SMAIII share many clinical features with these conditions, although the mechanism of muscle weakness is different. In this study, we investigated how patients with SMAIII respond to aerobic training.