According to the research done by Dr Christopher Snell and his colleagues at the Fatigue Laboratory at the University of the Pacific, aerobic exercise is just what ME/CFS patients should avoid, because of the metabolic malfunctions in their aerobic energy system. They recommend that people with ME/CFS stay below their anaerobic threshold at all times to avoid post-exertional malaise. http://forums.phoenixrising.me/content.php?246-Exercise-CFS-aerobic-VO2-Max-E-Word-by-Jennifer-Spotila&page=1 The fact that people with other illnesses may benefit from aerobic exercise really isn't germane to the question that was asked, and implying that ME/CFS patients would benefit from it could be damaging. Saying that aerobic exercise is the only kind that's beneficial is simply inaccurate. The goal for ME/CFS patients is to move and/or exercise without raising their heart rate enough to cross their anaerobic threshold, so that slowly, over time, they will be able to raise their anaerobic threshold. Then they will be able to increase the amount they can do without triggering PEM.