The problem comes from the fact that the psoas contracts many thousands of times every day, and unless we fold over backward, it never gets stretched. Both of these muscles originate on the lumbar vertebrae (low back), when either one of them goes into a spasm they pull on the vertebrae, and the pain is felt in the low back.
Since the erector spinae is stretching many thousands of times every day, it rarely goes into a spasm in the low back area – but it is common for the psoas to become contracted because of the phenomenon called ‘muscle memory’. In this case, the muscle memory for the psoas is to be contracted. As the muscle contracts in a spasm it pulls the lumbar vertebrae forward and down, and you feel the pain in your low back. People automatically rub their back, but the pain is actually coming from the muscle that is located on front of the spine, and behind your intestines.
This is the reason why the pain actually feels a bit better when you bend over – you are going into the contraction and taking the pressure off the lumbar vertebrae. But, when you stand up, the muscle is again pulling on the vertebrae: pulling the bone out of alignment; compressing the disks; impinging on the nerves; and you are also feeling the tug of the muscle on the bone. The muscle definitely needs to be stretched.
We have found that the psoas never gets stretched because the only way to stretch it is to keep your hips and legs completely straight and ONLY lean back at your waist. This is a very slight stretch; you aren’t looking to do a back-bend since you would need to move your pelvis and legs. While you will have discomfort along your lumbar vertebrae and possibly across the top of your posterior pelvis, only go to the point of a “feel good” stretch, not to the point of causing sharp pain. As soon as you feel the stretch go a tiny-bit further and then slowly stand up straight. Don’t hold yourself in the painful position. You will be able to go further each time you do it, and your back will feel better each time. You’ll be amazed at how quickly this helps low back pain.
To help yourself with positioning the first few times you do the psoas stretch, turn around at the sink – putting your calves up against the cabinet, and your hips resting against the counter. Keep your hips and calves gently touching the cabinet; also keep facing straight ahead, and lean back, moving your upper back over the sink.
Be aware to keep the pressure the same on your hips and calves, if you feel it increasing you will know you are leaning back with your lower body. Also, check to make sure that your weight is evenly distributed on your feet and you aren´t leaning back onto your heels. It helps if you place your hands on your stomach and lift up your chest, stretching your abdominal muscles. This will raise the spine a bit before you lean back. Do this movement 10 times. On the last stretch bend forward, arching your back and moving your hips side to side.