This stretching workout is good for runners because it stretches all the muscles you use while running. It is important to stretch before you run because if your muscles aren't stretched out and warmed up before you run you can pull something more easily.
Psoas muscle attaches to your lower spine and to your thigh bone. If it's tight (sitting too much?) it pulls your lower back. It's one of the common causes of lower BACK PAIN! If you can stretch this regularly then your lower back may feel a lot better!