Here is a great article written by Danielle Prohom Olson on the importance of the Psoas Muscle. I feel that when a client comes in with back pain of any kind, I need to work on this muscle and let them know how they can exercise to relax it. One of the ways I relax my psoas is to lay on my stomach with a tennis ball under my abdomen. I don’t push hard I just lay on it and breath for a few minutes or as long as comfortable if I am experiencing any pain. I just breath and allow my whole body to relax.