The psoas is a large muscle that reaches from the spine (just above the belly buttom) down through the abdomen and across the hips to attach on the inner, upper femur. The psoas responds to fear to pull the body into a protective, curled up position. It also becomes inflexible from sitting, running, cycling, driving and more. It can cause issues in the low back, hips, sacrum, SI joints and pelvis primarily.
Here's a few ways to release your psoas gently so that it doesn't spasm or recoil. Make sure you release both sides so you feel or see the same amount of flexibility on both sides, which likely means less time on the more flexible side. Make sure to not overdo it. The psoas responds to less not more stretching and be gentle!