The primary control

Dear Kevin, 

A great deal of work has been done studying movement in terms of biomechanics. Muscles are motors that move levers, and by analyzing the forces produced by the motors, we can analyze how movement takes place, gauge movement efficiency, and suggest ways to make it more efficient.

 But human movement is actually far more complicated than this because we are not just muscles and motors but a complex locomotor system that is balanced on two feet and capable of changing shape and moving in all kinds of ways. To balance on two feet, muscles have to maintain the body in an upright arrangement, but in such a way that the system is still completely mobile. The solution nature found to this problem was to place the head on top of the vertically-poised spine, but in such a way that the head counterbalances the muscles at the back of the neck, the spine acts as a lengthening device for the muscles of the back, and the muscles of the legs stabilize the struts of the legs but remain lengthened by the struts. This way, the entire structure is maintained upright, but at the same time, muscles are lengthened and not constricted so that the entire structure is mobile. The structure is then able to lengthen or support itself against gravity, and this is accomplished by the relationship of the head which counterbalances the neck muscles, and the spine, which lengthens against gravity as muscles act on the spine.

 Does this structure support from the ground up? Yes–but to do this it must also be organized from the top down, because it cannot maintain lengthened and efficient support against gravity unless the head is counterbalanced on top of the spine and the spine lengthens–that is, unless the head leads and the spine lengthens. So the structure is supported from the ground up but organized from the top down.

 This is why I do not think that analyzing movement biomechanically from the point of view of how we support from the ground up is a sufficiently complex or subtle concept to adequately describe how we move. Biomechanically we support from the ground up, because we have to apply force to the ground to come up off the ground; dynamically we support from the top down because the system cannot maintain efficient length in muscles unless it lengthens with the top leading upward and the spine lengthening. That’s why I said, in my earlier comment, that the main organizing principle in human movement is the relationship of the head to the spine: it is this basic relationship that organizes the muscle system dynamically in order to permit the body to maintain itself biomechanically from the ground up.

 Coincidence has it that I have a book which has just come out, which addresses many of the points raised above.  It’s called “The Body in Motion”–see the “Books” page on the site for details.

I hope this answers your question!

Best,

Ted Dimon