Have been pondering the deconditioning theory in relation to my own ME, though perhaps, given it is so obviously false, this is rather a waste of time.
My ME, of some 25 years standing, has followed a relapsing and remitting course, varying from one period some 19 years ago when I thought I was recovered to the last two years when I have been largely bed bound. Relapses can be triggered by single episodes of over exertion, prolonged periods of 'doing too much', infections or have no obvious trigger. Relapses can have a sudden or a gradual onset. Each relapse in general is worse than the previous, takes longer to remit, less of the original premorbid functioning is regained and over time I develop new symptoms.
I have always been someone who pushed myself to do as much as possible. I always seek to do as much as possible whilst trying not always successfully to avoid PEM. This does mean that I have no spare capacity to deal with unplanned major events, such as deaths or 'divorce', that demand high levels of activity and consequently result in relapses. I have been historically resistant to pacing, and still struggle to suppress my natural tendency to do too much. I did several years ago undertake a very useful course of CBT aimed at getting me to be more realistic in what I attempt to do, to avoid unrealistic expectations of what I can do, even on good days. In effect CBT aimed at countering my false beliefs about how much I should be able to do and aimed at getting me doing less.
If my ME is the result of false cognitions and deconditioning, why do these fluctuate so dramatically? Why do I have a conscious desire to do more than my body is capable of doing? Why do I too often do too much? Why have my symptoms increased over the years? Why do my false cognitions and deconditioning result in what appear to be random new symptoms, unconnected with my initial episode of glandular fever? (Some of the more recent new symptoms, on average one new one each year, include caffeine intolerance, symptoms of prostrate problems - may when bad need to urinate every 15 minutes, chostochonditis and pain in the muscles of the shoulders and upper arms. I take new symptoms to my doctor so that for example prostate cancer or a heart condition were when relevant ruled out. These additional systems do not gain me extra attention or sympathy, as once a medical condition other than ME is excluded, they are consigned to the hours or days when I am alone with my condition and are not raised with my doctor or anyone else again.)
How can the psychosocial model begin to explain a relapsing and remitting condition? How does it explain the emergence of completely new symptoms unconnected with deconditioning? I would argue that deconditioning is not a significant factor in the course of my ME and that any false cognitions I have involve a failure to accept the implications/limitations of a long term disabling condition, diametrically the opposite of that proposed by PACE advocates.