The QL (Quadratus Lumborum) is a muscle in the back part of the abdominal wall, and is often overlooked as the cause of back pain.
Since the QL is a deep muscle, it can cause alignment issues as well when it is injured or irritated.
For the first QL stretch, getting your legs into a butterfly position will help increase the stretch, but you don’t have to if you have really tight groin muscles.
Then put the leg of the side you want to stretch out at an angle for the next two stretches. You can stretch over to the opposite side, and you can also add a rotation for more of a stretch.
The fourth Quadratus Lumborum stretch is a little tougher, and if you have other issues (knee or hip pain), you might want to hold off on this one.
The last QL stretch is a little easier to do since you have the floor to help keep your hips in place. Pushing up when on your side will give you a great QL stretch.