Walking backwards, and quartered to and fro, on a treadmill (or running hillsides) has proven to be one of my more effective back injury prevention practices. As well, keeping the hip flexors stretched helps. I once saw them using a similar harness supported treadmill therapy on people at a spine specialist, during their recovery. Tried it, and along with strengthening the low back and glutes-alleviating back pain, I also stopped having troubles with damaged menisci, and it strengthened my feet's arches, resolving some fasciitis