My back feels quite weak, especially while sitting. I always thought it is caused by the weakness of the deep muscles, which stabelize the spine. Maybe poor blood perfusion or something else. I guess this could cause a lot of trouble over time. The deep muscles have three or four layers to give the spine more power.
That's interesting. My posture has tended to be pretty good, but when my excess fat decreased, and muscle strength and flexibility increased, following commencement of my leaky-gut regime, my back muscles were amongst those that I became more aware of again - in a good way, in that I can once again stretch them when I wake up, for example.
Another extraordinary consequence of the leaky-gut regime is that I now need walking sticks 2 inches longer, and can't imagine how I managed with them shorter! I don't seem to have grown taller (pity), but guess that improved musculature has raised my shoulders.
Incidentally, depression can be caused by high levels of interferon (which some of us appear to have), and anxiety can be significantly reduced by a leaky-gut diet and supplements, and many of us have leaky gut/IBS.
So these co-existing 'affective disorders'/'mental illnesses' are, I suggest, simply different manifestations of the same imbalances/physiological abnormalities as the ME/'CFS' itself. Maybe some of the other 'co-morbidities' are too.
Perhaps an example of the shortcomings of modern medicine's definitions of illnesses.