In the child with a neuromuscular disease (NMD), one can use exercise for the assessment of physiological function and as a therapeutic modality. Functions most relevant for assessment are muscle strength, muscle endurance, peak mechanical power, and O2 cost of movement. Maximal aerobic power is less important because it seldom is the limiting factor in the child's ability to perform daily physical activities. There are very few well-designed controlled training interventions in children with NMD. There is, however, some evidence to suggest that maximal aerobic power, muscle strength, and O2 cost of locomotion are trainable in children with NMD.