Tony Judt, author of the magisterial book Postwar—really, one of my absolute favorites—has Lou Gehrig’s disease, and it’s progressed to the point where he can’t move his arms or legs.
In the NYRB, he writes:
During the day I can at least request a scratch, an adjustment, a drink, or simply a gratuitous re-placement of my limbs—since enforced stillness for hours on end is not only physically uncomfortable but psychologically close to intolerable. It is not as though you lose the desire to stretch, to bend, to stand or lie or run or even exercise. But when the urge comes over you there is nothing—nothing—that you can do except seek some tiny substitute or else find a way to suppress the thought and the accompanying muscle memory.
But then comes the night.