SACH-SAWCH

The built-in Gears (gait harmonics) Bottom-up: Forefoot - ('met heads') to ankle center is the spoke of that wheel. (Axis at end of foot) Heel - Heel tip to ankle center is a spoke of a second (smaller) wheel. Shin - Ankle center to knee (shin) is the spoke of a large wheel. Femur - Knee to hip joint ( spoke of a femur wheel ) CmH - Center of mass (an inertial reality without a visible presence) to hip center. This top wheel spoke is nearly the same as the forefoot wheel. Can swap. Being of similar size the CmH & forefoot wheels are able to share adapting to the smaller ground changes. If the forefoot is insufficient then the CmHip wheel gets the remains. This is why vertical hip motion is so prominent wearing high heels as available ankle range is used up by excess plantar-flexion. Lumbosacral fusion makes the wearing of high heels close to impossible. Likewise, high heels produce vertical pelvic oscillation, maybe a goal in itself? The wife of a famous spine surgeon had a lumbosacral fusion after injury in a plane crash. She asked, “Why is it I can't wear high heels anymore?” Answer, “You're married. You don't need them anymore.” No. It didn't go over well. The long explanation followed, which you just suffered through.