If you have lower back pain, pelvic tilts are great for stretching out your muscles. There are several ways to do them but I prefer to get on my hands and knees. Then I slowly tuck my rear end under a little by contracting my abs. My lower back feels pretty good afterward.
I've had two back surgeries and have rods and pins in my back. Several physical therapists have recommended these as one of the best ways to help pain. I can't do them the way described here but I can do them while laying flat with my knees bent. It's usually the first thing I do before I even get out of bed in the morning.