The Quadratus Lumborum (or QL for short) is a muscle that is often tight in those who suffer with lower back pain. Carrying your bag on one side, leaning on one elbow when sitting, favouring one leg too much when standing, sleeping on your side... ALL of these can lead to stiff QL. Best way to help it RELAX?... S..T..R..E..T..C..H it out!! Hold for at least 30 seconds. Repeat 3 times on each side.