Loving and caring for your psoas (pronounced so-az) is a worthwhile intention in your yoga practice.
The psoas muscle lies deep within, connecting to the spine and leg bone. It is a large and intensely important muscle that connects the top half of your body to the bottom half, and the back of the body to the front.
A healthy, flexible psoas has much to do with ease of movement; alleviating lower back pain, including sciatica; and healthy breathing.
One of the best illustrations of the psoas and how it works is a post by Todd Norian, linked below. I have taken a number of workshops with Todd. He is terrific, and I thank him for sharing his knowledge.
Judy Gudmestad shows us how to locate, strengthen and stretch the psoas in this article.