Mark Twain loathed exercise. “Whenever I get the urge to exercise,” he is said to have remarked, “I lie down until it goes away.”  He did acknowledge that his approach was not right for everyone. Beyond the intended humor of his remarks, we now understand that complete inactivity has tremendously deleterious effects on the body, even for patients in intensive care units. Early mobilization of even the sickest hospitalized patients is now being undertaken to reduce the high rates of fatigue, muscle weakness, and tachycardia after severe critical illness . The ability to tolerate exercise is a key component of good health, and few would argue with the observation that regular exercise is an important part of a healthy lifestyle. But there is a paradox about exercise for those with chronic fatigue syndrome (CFS). While most studies show a modest benefit of graded increases in exercise on CFS symptoms (at least for those healthy enough to participate in the studies), a defining feature of the illness is worsening of fatigue and other symptoms after activity. For many with CFS, especially those who have more severe impairment, a major challenge is to find a way to bridge the gap between their post-exertional worsening of symptoms  and being able to tolerate the kinds of activities that common sense and the available evidence tell us should be helpful.
By Peter C. Rowe et al