Where did those muscles come from?

I have been in physical therapy for the years and years, mostly for my legs, especially my right leg.  It has been paralyzed multiple times.  With lots of PT and IVIG, I regain my ability to walk at least some.  I've had paralysis in every extremity in my body at some point over the last 10 years.  The majority of the exercise I get come from PT exercises and a recombant bike at a slow pace for 20-30 minutes most days.  These are not the kind of work outs that can make a person sore.  This is why I was very surprised when just a day of rehab made me very, very sore.  I started getting a little sore after my first 2 hours of PT/OT yesterday.  We did core work almost exclusively.  I took some Tylenol and felt better.  This morning though, I was very sore.  My back and obliques hurt a lot.  It's not my normal back pain.  My abs hurt too.  I guess that is what happens when those muscles are paralyzed for a few days, then have to be strengthened.  I feel like I did 500 sit ups.  I guess the soreness is worth it is because my trunk is stronger today than it was yesterday.  I can hold myself up for several minutes before I start to drift.  Do you know what the worst thing about being sore is?  Being in the hospital, I am limited to what the doctor orders for pain and they only ordered Tylenol every 8 hours.  Who gives Tylenol every 8 hours?  I need to get this changed as soon as I  see Dr. Latorre in the morning.