Years ago at chiro college, I had to do a presentation on core stability. Fortunately, for me, I had just picked up a copy of Dr. Stuart McGill’s Low Back Disorders: Evidence-based Prevention and Rehabilitation. What a gem!
Anyway, I read his book and knocked the presentation out of the park. Years later, the information that I presented and ultimately in Dr. McGill’s book is just as relevant as it was back then.
For those of you who haven’t read it, READ it.
A concept that Dr. McGill presents in his book is that the muscles that protect and stabilize the spine are arranged like guy-wires, similar to that on a ship. These guy-wires hold up the spine on all sides, exerting balancing the forces.
Which is the best muscle or muscle group to stabilize the lumbar spine during the squat?
The erector spinae? While it’s true that the erector spinae muscles extend the spine, their distance away from the spine may create instability.
How about the abs? The rectus abdominus (and obliques), similar to the erector spinae lay a certain distance away from the spine. Again, they create global movement at the expense of intrinsic stability.
What about the iliopsoas? Believe it or not, the iliopsoas or hip flexors will best stabilize your spine during a squat. First of all, they extend the top three lumbar vertebrae, maintain the 4th in neutral, and create only slight flexion in the fifth.
More importantly, since they lay close to the spine, their contraction actually compresses the spine, creating more stability. Keep this in mind – the iliopsoas compresses and extends the spine (compression and flexion are dangerous).
As you set up for the squat, extend your spine from the inside. In other words, extend your lumbar spine WITHOUT using your erector spinae. Now hold this contraction…during the setup…on the way down…and on the way back up.