Contrary to conventional wisdom, certain kinds of exercise may be beneficial for patients with neuromuscular diseases, according to UC Davis physician David Kilmer, who specializes in physical medicine and rehabilitation. It's a mystery to medical researchers and clinicians why some patients thrive by ignoring their doctors' advice and pursuing strenuous exercise while others decline at the least bit of exertion. "We need to know why they can get away with it, and whether we should be telling all our patients to keep running and skiing and biking," Kilmer says. "Our research suggests a particular sensitivity to 'eccentric' exercise, the kind that involves lengthening the muscle fibers, like when a weight is lowered through a range of motion." This kind of exercise -- the kind you get when you trek downhill -- can damage muscles in even the healthy and well-conditioned. Kilmer suspects the key may be found by closer examination of the muscle cell membranes, known to be damaged in eccentric exercise and thought to be the site of a defect causing many muscular dystrophies.