Interesting topic.
When I was able to start exercising I had to be quite disciplined to not raise my heart rate to high, if I stayed at the upper end for to long it took days to recover.
I had to be content swimming an easy pace which was a lot better than zero exertion for 2 years.
It did take a couple months to arrive at that conclusion.
7 years later there are still certain limits but I'm willing to live with the repercussions, some weight exercises can bother the localized accident area, I believe it is muscular and not neurological.
One of the funny things that I encountered....I couldn't wait to get back to the gym and knew what I wanted to do with weights, remembered all that but the sensations of tired and sore muscles afterwards or lifting to fatigue where foreign, had to relearn those sensations were safe and a normal part of exercise.
Have fun.