Core, Pelvis, and Midsection by Ken Blank

The psoas may be the body's most essential muscle. It is the only muscle in the body that connects the legs to the upper body. The psoas is worked with core building exercises in fitness classes and brings balanced muscular action to the core, pelvis, and midsection.

There are two psoas muscles, one on each side. Each originates on the side of the spine from the 12th thoracic vertebrae to the 5th lumbar vertebrae. The psaos runs thru the pelvis, inserting on the lesser trochanter (bony ridges on the upper, inner femur).     

The psoas is a postural muscle, acting as a hip flexor, shortening when lifting the knee and lengthening when extending the hip.  A short, tight psoas can cause (1) pain in the lower back or hip and (2) the thoracic and cervical spine to pull forward and down, making a yoga practice uncomfortable and difficult.  A healthy psoas is strong and lengthened, allowing the whole body to open. 

The psoas can be visualized as having two sections, one from the lesser trochanter up to the 5th lumbar vertebrae and the other from the 12th thoracic vertebrae down to the 5th lumbar vertebrae. Because the psoas is a postural muscle it must be eccentrically lengthened. (For a discussion of concentric and eccentric contractions see blog #3, An Alignment Principle to Balance Muscular Action.)  To eccentrically lengthen the bottom portion of the psoas, concentrically engage the glutes, the muscles at the base of the pelvis, and the lower abdominals—in that order. To eccentrically lengthen the upper psoas, concentrically engage the upper abdominals and the obliques (muscles on the side of the waist), then the deeper transverse abdominis. (To feel the action of the transverse abdominis, pretend to suck on a straw.) Because the psoas naturally contracts as it lengthens (an eccentric contraction), engaging the opposing muscle groups (muscles surrounding the pelvis and waist) as described above will  balance the muscular action in the core, pelvis, and midsection.

The Quadratus Lumborum (QL) is another postural muscle. The QL inserts on the back body at the bottom of the 12th rib and originates on the top of the pelvis. It runs parallel to the upper portion of the psoas. If the QL is short and tight, it tends to pull the back of the rib cage down. 

The QL opposes the same muscles as the upper portion of the psoas. The actions taken to eccentrically lengthen the psoas will also eccentrically lengthen the QL.  Therefore, if the pelvic muscles and the muscles surrounding the waist are concentrically engaged, the psoas and quadratus lumborum will eccentrically lengthen.  These engagements can be applied to any yoga pose to balance the muscular action of the core, pelvis, and midsection.


Stay Tuned! Next Blog: Shoulders