Form and Force

I was talking with a client about the purposes of an exercise and it brought up a couple of terms that I want to share more widely.  We get stability from our bodies in at least two ways:  form closure and force closure.

 

Form closure is how our bones fit together.  For example, at the back of our pelvis, the sacrum (base of the spine) fits like a wedge in the slot between the two halves of the pelvis.  This is stability by design and unless something goes seriously wrong with our bones, we don’t have to do anything about it—we can’t really do anything about it.

 

Force closure is something we have a bit more influence over.  Our bones are connected by ligaments (directly), and tendons and muscles (less directly).  When we work with muscles around a joint using good form, we are improving our force closure.  In other words, hip exercises improve the stability of our hips, shoulder exercises keep our shoulders stable, and so on.  The extra good part about force closure is that it is about stability in motion—we want to be able to move those joints, not live our lives as stable statues.

 

Let’s be strong, stable, and mobile!