A team of researchers in London studied the composition of muscles and changes in muscle fibers and lactate production following exercise in patients with CFS to determine to what extent any abnormalities might be due to inactivity. Their analysis of muscle fibers did not show the changes that would be expected from inactivity, and there were no abnormalities in the mitochondrial structure. Also, the type of muscle fibers that were more abundant was not typical of a sedentary person. The pattern of muscle fibers they found “is in keeping with other reports concerning reduced oxidative metabolism and mitochondrial enzyme activity in muscle in some patients with CFS,” the researchers concluded.
Lane, R., et. al., (1998). Muscle fibre characteristics and lactate responses to exercise in chronic fatigue syndrome. Journal of Neurology, Neurosurgery and Psychiatry, 64, 362–367.