The Psoas Muscle in Walking
Biomechanical and Fascial Considerations
In my DVD, I speak several times about the importance of propelling the body forward with the back leg and foot, allowing toe-off to be complete. It’s common, in places where space is at a premium (e.g. crowded sidewalks, corridors between work cubicles, small kitchens) for us to pull ourselves forward with the leg that swings forward, rather than propelling our bodies forward from the back leg. When the body is drawn forward from the forward heel, the hamstring muscles don’t complete their potential for movement which is to extend the hip enough to take the leg behind the body. When the hip doesn’t fully extend, the hamstrings are robbed of the opportunity to let go during the swing phase of the walk. This is the scenario of perpetually tight hamstrings. (Watch examples in the last moments of this video post from last year.)
In the above described gait pattern, the distal attachment of the psoas at the groin becomes a fixed point. With every step the psoas stabilizes the trunk: the thigh pulls the trunk forward but because of the truncated push-off, the psoas remains short and tight and doesn’t lengthen to its full extent.
When you push the body forward and really extend the back leg behind, you activate the hamstrings, gluteus maximus and foot plantar flexors. That action elongates the psoas, a natural antagonist to the hamstrings. The psoas fascia is then stretched during push-off, and the energy thus stored rebounds to swing the leg into the next forward step. When the psoas fascia isn’t lengthened during hip extension, its ability to store and rebound energy is wasted.
None of this works unless ease in the ribcage allows respiration to lengthen the spine and free the ribcage from the pelvis. Elevation of the ribcage raises the proximal attachment of the psoas, lengthening it. Normal contralateral rotation of the spine during walking takes place just above the place where the psoas and diaphragm fascias interweave along the front of the spine. Thus breathing well and walking well are inextricable.