They're deep and if we use them incorrectly they cause us pain. What are they? They are rectangular shaped muscles (hence 'quadratus') situated in the lower back Where are they? These muscles run on either side of the spine from the base of the ribcage and the lumbar spine down to the top of the pelvis.
What do they do? They are part of a series of muscles which support and protect the abdominal cavity. They also assist with stabilizing the spine, allowing the pelvis to tilt and with breath control. When they contract they create extension through the spine - leaning backwards - and if they contract on one side only they cause a side lean.
How do I activate them? As the Quadratus lumborum muscles are used predominantly for support and stability, they are usually switched on semi-permanently. We should think less, then, about how we activate them and more about how we ensure they can do their job properly. Overuse of the Quadratus Lumborum If we fail to train our other back muscles by slouching, or otherwise weaken the back through injury, sedentary behaviours or illness, we can come to over-rely on this muscle group to support our back. The quadratus lumborum can then over-tense and create lower back pain. This can be relieved by stretching through these muscles with side bends and rotations, while strengthening the other back and abdominal muscles with extensions and static holds (think every Pilates class EVER!).
Why do we need them? They allow us to both stabilise and control movement around our lower back. Without these muscles it would be hard to stabilise to create the weight or resistance bearing movements which strengthen our overall musculature.