I have been looking for lower-risk activities than weight lifting. I gave myself 2 impinged shoulders, and severe tennis-elbow over the course of only 1 or 2 months of lifting.
My first thought was rowing, however lower back injuries are really common among rowers. I have been rowing for about a week, and I can already feel what is "bad" soreness (as opposed to "good soreness", not "severe soreness") in my lower back.
In lieu of having anyone reputable to ask, the advice I'd give myself is stick to walking, preferably not on a treadmill. Do lots of stretching. Add cycling when I want to do a lower-impact, or non-weight-bearing activity.
That's it.
Update/Edit: I have continued to row approximately every other day. I haven't increased the volume or intensity from what I started with. I am paying extra attention to technique and drills - in particular body preparation at the finish. I seem to be doing fine.
