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The Role of the Stirrup Spring System
Consider this counterintuitive structural explanation for piriformis pain and pelvic obliquity. July’s e-newsletter described the antigravity function of what I reference as the Stirrup Spring System (SSS).
Notice in figure 2 how the biceps femoris muscle fires just prior to heel strike and pulls on the tibialis/peroneal stirrup to elevate the arch. During heel strike, force is transmitted back up through the lateral thigh and sacrotuberous ligament. With the help of the piriformis and other hip rotators, they right rotate the pelvis causing reciprocal left rotation of the lumbar spine.
If the bones, muscles and fascia of the foot, ankle, and knee are aligned and functioning properly, kinetic energy is transmitted unimpeded though the pelvis and all is well. However, any kink along the kinetic chain such as a flat foot, displaced fibula or fixated hip capsule will diminish the pull on the sacrum.
This loss of energy from below causes the hip’s external rotators to overwork in an effort to rotate the pelvis. Soon, myospasm and contractures develop in all sciatic notch musculature setting the stage for nerve trunk impingement. |