I just got over a bout with back pain, and I think I attribute it to doing squats. I've taking a new stretching regimen with emphasis on my hamstrings and lower back to keep my lower back loose. I've started light on the Smith machine. Any hints to get back on the squat rack without giving me the back pain? Sadly I was only doing 135# (3 sets x 20 reps) on the squat rack when I hurt my back.