We now have two reputable exercise laboratories which have separately published results of two-day cardiopulmonary exercise tests showing the reality of a drop in anaerobic threshold of ME/CFS patients on the day after a first exercise challenge. This is so striking the researchers involved said they went back and recalibrated their equipment, because they had trouble believing what they were seeing. I am not here to dive into the on-going scrum about using this test for diagnosis. I want to ask a different question. These are basic physiological measurements. The researchers have been doing exercise testing for many years, yet still expressed surprise bordering on shock at these results. Why has this not been previously documented? Is it plausible that a million or more people with this condition in the general population have never showed up in tests run for other purposes? One answer would be that this is a new disease or epidemic outbreak, with characteristics never seen before. (I doubt this, but I'm willing to consider the possibility.) Another possibility is that reasoning of the sort "healthy people exercise more" => "exercise improves health" has never been widely tested because expressing doubt on the subject would weaken the effect of medical exhortation about exercise, which is generally a "good thing" for most people, most of the time. If it had been carefully tested, and if incidence of ME/CFS has remained roughly constant, then the absence of earlier results of this kind -- in any medical condition -- would be inexplicable. (I'll admit to having a prejudice here, but I'll listen to reasoned arguments.) I can certainly report that doctors have advocated exercise for me -- even when I had flu-like symptoms. At the time, I thought they knew what they were talking about, but I've since seen enough evidence about patients with myocarditis presenting with similar symptoms to wonder how they can be so sure this is not such a case, where exercise can actually be fatal. The fact that a patient has recently passed a physical is not much of a guarantee. I've also seen patients have heart attacks a week or two after a physical with lab work and an EKG that said they were in good cardiovascular health. This is not a rare sequence of events. Most clinical tests only detect damage after it has occurred. They have poor predictive value, if there is no previous damage. My suspicions were aroused by publication of a study claiming aerobic exercise was beneficial for both MS and ME/CFS, without ever checking for any effect on anaerobic threshold. The "subanaerobic exercise" challenge they used was based on data from the healthy population. They had no idea if this truly was below anaerobic threshold for the patients they studied. Since anecdotal material about the effects of overexertion on MS patients is widespread, I wondered if this was an isolated lapse or evidence of a systematic pattern of research neglect. What I'm asking here is for help in researching the state of the art. How much effort has gone into distinguishing exercise as a measure or consequence of health from exercise as a treatment promoting health in any medical context? If I reach a conclusion I will post a blog entry covering the subject. You can either post references here or you can send me a PM. You can even send email to my handle on this forum via gmail.com.