No use pushing too hard
I am not a doctor but a recovering/recovered GBSer. Prior to having GBS, I worked out 5-7 days per week including lifting weights and jogging.
As such, after coming out of the hospital, I was very focussed on getting back to the gym and working out.
What I learned what that no matter how much I worked out, my muscles needed a long time to regenerate/recover, literally months.
So in hindsight, I would recommend working out, but not too much as (i) possible to get too drained and relapse and (ii) initially the muscles will take a long time to regenerate, so there is not much point in working out a lot.