SACH-SAWCH

The 6 determinants (of Inman): The capacitor in the ankle (heel/foot) is #6

but we re going ground up, so?

As the heel hits and the ankle lowers and the foot drops flat to the ground we get some height reduction, a lower

radius of arc to travel over. As mass moves forward, above, the calf becomes quite tight and freezes further ankle motion (passive dorsiflexion stops with the shin about 8 to 10 degrees forward tilted – knee center is forward that of the ankle with center of body mass CENTERED on the foot [heel contact to metatarsal heads]. (Not included by Inman, but obvious, toes are feelers not do-ers. Forward roll is over metatarsal heads not toes.). Got that? Toes are detectors. Not doers. Don't blind them. The calf, by making the ankle mechanically solid, diverts the forward roll to over the forefoot (MT heads). That roll lifts the heel which rises off the floor just as center of mass has passed the mid foot. This would otherwise now be a roller coaster car at the top of the first hill. The supporting leg rising – AT THIS POINT – lifts and so flattens the top of hill drop that would otherwise follow. ' Midstance ' is when our center of mass is over the point of floor support. But,for quick eyeballing, use hip over midfoot as close enough, visually. In our method, MIDSWING is when the swinging ankle is at same forward point as the stance ankle (one hides the other on side view).