Yes, during the treatment, treatment can always be adjusted according to what you can handle. I had to have PT for 8 months because my upper legs were getting thinner (initially the right one more because I had a cast and knee surgery on that side). They first started with barbells and special contraptions, but that got too heavy fast and I couldn't bare it (I had RSD), so they did electro-stimulation and infra-red from then on.

I got no treatment for RSD back then, just the PT (there was nothing else they could do at the time as they had no clue what was wrong with me at that point) and by the time I was through my upper legs were thinner than my calves - and I have slim calves.

Yeah... those days were awful. But my point is, they can adapt your treatment during the treatment too, if YOU indicate it is not do-able.

Later of course they found out I had RSD but by that point it was too late basically to revert the disease in my legs as it had become chronic and disabling.