SACH-SAWCH

A journey, from SACH to SPMLs

You don't need feet to walk. That was the title of a lecture to our podiatrists in NY & NJ. Simple proof? Amputees running races as fast as anybody else aside from walking to and back from those races – without “feet”. That capability was no accident. Soldiers coming back from the war with parts missing and a need to make them whole again led Inman (et al) to do the seminal work on what did feet and legs actually did. Not so much how big or how fast but what ? There are all kinds of possible make-do things – peg legs for example. However, those were very limiting and the common limiting element was ENERGY. You can do things badly, even quickly. But doing so costs you energy. Disability is more often an inability to sustain the thing you can do. So, the answer was sought to a better question. What do feet and legs do that, working together, conserves energy? When you move the body through space A===>B a steady flat line would seem ideal. Wheels on a chair? Nice, but, not so good when A===>B is through the woods. The anthropologists have not actually caught on (yet) that bipedal-ism is about energy . Long tails to allow bipedal balance are also about that as well. Permissive. Short arms on a toothy predator? Same thing, bigger arms need a bigger tail to balance. Center of mass wants to be close to the two hips axis (if you have hips). It was a neurological development which allowed the modulation of the leg movement mechanism through detected and anticipated momentum and inertial requirements.