--is a common symptom of almost any neurological disorder. The most well-documented occurences are with multiple sclerosis, but are hardly limited to it.

In any case in which there are erroneous nerve signals--due to de-enervation of the muscles, damage to the sensory nerves, whatever--correspondingly more effort must be made to manage and use the muscles and to effectively notice and utilize the propriceptive body signals/feedback that most "normal" people take for granted. This also involves using muscles that are not normally involved in certain motions/positions in a compensatory way, and this adds strain to them. Moreover, de-enervated musclature simply involves more energy to get going and keep moving, as the proper efficient signals are not getting to them.

I've personally found that keeping muscles as strong as possible through exercise helps, although this must be done to individual tolerance. Having a good vitamin staus, especially of the B's, which promote nerve structure and mitochondrial energy release, also is useful.