This piece serves as the follow up to How To Push Down.
When we are talking about compression, we are also talking about tension. It is the interaction of these two push-pulls that creates suspension. Otherwise everything would collapse. These three revolving concepts: compression, tension, and suspension is the concept behind tensegrity.
If you watched at least 2min of the video, you noticed how a shortening of one rubber band created length in another. Since the insertions and origins of muscles are fixed (a brilliant insight by Adarian Barr) how does a stretch actually occur? It must be a positional adaptation of the stacking of the structure — the joints have shifted out of balanced alignment. Too much tension in one place has shifted the skeleton (the black frame from the video) to ‘sit’ skewed.
Posture plays an enormous role in what our bodies are able to do. How it holds itself is a result of time and tissues. Some tighten, some slack. Gravity is a constant compression force. Whichever lines are used to keep the body upright (neck tension, anyone?) will stay tight even with the position changes (sitting to standing, for example). The slack lines, then, will also stay slack. A spillage or sliding of the bones result.
Imagine if the structure wasn’t a uniform cylinder and certain segments were displaced left, right, or diagonally.
Without the directional pull of gravity, the slinky expands and contracts three-dimensionallly (following the external trajectory imparted on it by the hands):
Newton, everyone. A deeper explanation can be found here.
Now let’s consider these concepts within the body.
First, the displaced cylinder of the torso. The slouch spills the midback and drops the xiphoid, compressing the low back into flexion.
Lifting the xiphoid pulls the ribs up and forward, extending the spine through the pelvis. The torso keeps this shape and structure while the arms and legs move about.
Without the suspension of the xiphoid, you cannot compress the middle to push or pull the pelvis.
Like the bird that balances on its beak, a lifted xiphoid pushes down on the area below it.
Regarding the feet, we circle back to the lift-holding strength of the arches.
Each half of the foot can load folded or compress by suspending the other half:
Loading the fifth metatarsal or the pinky ray is a bit different, but we’ll save the intricacies of this special digit for a separate post.
Note how the center of mass shifts when suspension is paired with compression. Without a down, you get a forward, back, left, or right. Something must move to realign on a smaller base. This is why Adarian constantly preaches “go down” — a drop in one place creates a lift in another — so the structure can support itself vertically under changing conditions.