Muscle fatigue in animal models of neuromuscular disease

This review summarizes the literature regarding the fatigue properties of skeletal muscles in animal models of neuromuscular disease and the effect of exercise training on these properties in diseased muscles. Results of these studies are not consistent. Reasons for the variability may include the use of differing experimental conditions, varying stimulation protocols, different methods of muscle preparation, and a range of temperatures and ages. Despite the variability and small sample sizes, these studies of muscle fatigue have revealed definite trends. Whereas the slow oxidative soleus muscle from the diseased animals fatigued more slowly or at the same rate as controls, the extensor digitorum longus (a fast, glycolytic muscle) from the diseased animals fatigued more rapidly than controls. The diaphragm-a fast, oxidative, glycolytic muscle that is generally fatigue resistant-did not reveal significant changes in fatigability. Exercise training had a minimal impact on the fatigue properties of skeletal muscle from diseased animals. As molecular and biochemical mechanisms are further identified and defined, additional therapeutic interventions may become available for these disorders. It is hoped that this review will serve as a guide for investigators who use an animal model to evaluate interventions for neuromuscular diseases.