You’ve probably never heard of it, but it’s an essential part of human movement, and one of the most ignored structures when it comes to lower back pain.
So, what is the posterior oblique sling?
The posterior oblique sling (POS) is a chain of muscles and fascia that runs across your back and into your gluteal region, and is one of many myofascial chains within the body. Formed by your latissimus dorsi on one side, and the glute max of the opposite side, along with the thoracolumbar/thoracodorsal fascia inbetween.
These slings cross over, creating an X across your lower back, which helps to provide stability to the lower back as well as supporting lower extremity movements.
The POS is an essential part of the gait cycle and is the reason that as you step forward with one foot, the arm on the opposite side swings forward. This action places the POS on stretch, and as it recoils from the stretch it propels you forward as you swing your next leg forward. This is an energy saving mechanism, as it means that for a large part of the gait cycle, we use the stretch and recoil of the myofascia instead of actually contracting muscles to move. This effectively reduces the metabolic cost of walking and makes walking and running for efficient. This is one of the many reasons humans are able to be bipedal.
So how does the POS affect your lower back?
Well contraction of the POS tensions the Thoraco-Lumbar fascia, a structure that is designed to stabilise the lower back whilst we move. So by making sure we have a strong and functional POS, we can help to stabilise our lower back.
The POS also travels over the Sacro-iliac joints, a common source of lower back pain. Sometimes this joint can be particularly sensitive to the forces applied to it, and in some cases a strong POS supporting it will be beneficial in minimizing the stress on the joint.
So, how do we strengthen our POS?
There are a number of exercises that will strengthen your POS. My personal favourite is the single-leg romanian deadlift. It sounds complicated but in reality the whole movement is using one hand to reach down and touch the opposite foot whilst keeping your standing leg strong and slightly bent at the knee. If you check out the Alpha Health instagram in the coming days there will be a video demonstrating the exercise (follow the link at the very bottom of this page to our Instagram account). The reason I like this exercise is that its so adaptable to every level of strength. For someone just beginning you can use no weight and keep both feet on the floor. Then we can progress to lifting the non-weight bearing leg and finally doing the movement with weight.
The POS isn't the only myofascial chain the helps to provide stability to the lumbar/pelvic region. Keep an eye out for future blogs and posts looking into these other structures!