One of the PTs had me doing light weights while laying on the table/bench and lifting up so that is like how you describe.
I started with 1lb and was able to progress up to 8 lbs in a couple weeks
We only started that after pain was down @ 1-2 though.
but slow and steady and only to fatigue & ability to do it without any pain increases.

Treadmill/walking doesn't bother me at all - but any bouncing/jumping or wild/fast arm movements do bother me.