Tensegrity, Biotensegrity and You

Tensegrity is a type of architecture, and here is how it was described by its inventor, R. Buckminster Fuller:

The word "tensegrity" is an invention: a contraction of "tensional integrity." Tensegrity describes a structural-relationship principle in which structural shape is guaranteed by the infinitely closed, comprehensively continuous, tensional behaviors of the system and not by the discontinuous and exclusively local compressional member behaviors. Tensegrity provides the ability to yield increasingly without ultimately breaking or coming asunder.

Huh?  Fuller was saying that a tensegrity structure consists of things (like bones, for example) that can resist compression, and things (like muscles, for example) that can resist tension. (I'll keep using the Bones/Muscles examples as I explain.)  Even though there are many bones piled up which keep your head over your feet, there is no single bone that goes from foot to head. If you always stood perfectly straight, your pile of bones wouldn't need anything else to keep it from falling over. But once you bend anywhere, it starts to get very difficult to trace exactly how the force of gravity travels from your head to your feet. I mean that all of the muscles and ligaments that you use for balance spread the forces out in complicated ways.


For example, when you bend your forearm, some of the force that allows your arm to bend is transferred to the upper arm. But this simple action has changed the way that the upper arm pulls on the shoulder, and the shoulder on the muscles that support it, etc, etc. Figuring it all out exactly is much more complicated than you might think.
Here's what is going on: The bones are very good at withstanding compression. After all, they were designed to support the body against the compression of gravity. They also resist the compression generated by muscles. Unfortunately, unless they're all piled up straight on top of one another, they do not form a continuous structure (that is, they are "discontinuous" from each other.) Muscles, on the other hand, aren't very good at handling compression (they'd just buckle and fold.) What muscles are good at is pulling on things. That is, they're good at handling tension.


Remember that many parts of the body have to adjust whenever a single simple movement is made. This happened because the muscles act as a continuous system where on muscle pulls on one bone, which pulls on another muscle, which pulls on another bone, and so on. Without the muscles to keep everything in its proper shape, everything would tumble down like a bunch of sticks. Looked at from this perspective, it's the things that provide the compressive forces that give the body its shape.


You Use Tensegrity!
A bicycle wheel is a familiar structure that happens to be a tensegrity. The wire spokes are "tension-loaded" while the hub and rim are "compression-loaded." That is, the hub "hangs" from the spokes. This explains why the few flimsy spokes don't just crumple when you hit a bump: The spokes can't retain their shape with much force pushing on them, but can easily withstand lots of force pulling on them.


Now let's throw something else into the mix: Your high school teacher described the musculoskeletal system to you as a bunch of levers and pulleys. However, if you want to think about the musculoskeletal system as just levers and pulleys, you are going to have some 'splainin' to do. This is because there are a number of places (particularly in the spine,) where calculating the forces generated by movement just in terms of levers and pulleys and fulcrums, results in such extreme amounts of force that the muscles should just tear off the bones, and the bones should shear into pieces! But since they don't, there must be something else going on too.


Your Fascia=Your Shape.
In the case of the whole body, that something else is the "fascia," which is the support and wrapping material for the soft-tissue in the body. All of the body structures are covered with layers of fascia, and it is a very fascinating fact that these layers are continuous throughout the body. That is, the same fascia that covers muscles in the leg is directly connected to fascia that covers muscles in the neck! (In fact, not to get too graphic or anything, but there is actually a direct connection of fascia between the cranial bones and the testes! )


The point of all this is that it's not just the muscles that hold the bones together. It's the whole system of fascia. It stretches, slides and supports the body in all of its movements. It gives the body its complete shape. At least it's supposed to.


However, through bruising, tearing and scarring, parts of the fascia can become bound to other layers. These are known as "fascial adhesions," or just "adhesions." Remember how I mentioned that it is difficult to accurately measure how changes in posture cause forces to be distributed throughout the body? These adhesions cause changes in the distribution of forces, and that can change the way the body moves. And that can result, for instance, in a case of whiplash resulting in a sore knee!


Tensegrity at the Cellular Level.
O.K., that's on a macro level. Now let's look at the micro level. Donald Ingber, M.D.,Ph.D. is a professor and reseacher at the Harvard Medical School. He is very interested in tensegrity because it helps to explain the cellular research that he does. Here's how he explains why: Cellular Tensegrity Theory. Cells and tissues are organized as discrete network structures, and they use tensegrity architecture to mechanically stabilize themselves. In the cellular tensegrity theory, complex mechanical behaviors in cells and tissues emerge through establishment of a mechanical force balance between different molecular elements in the cytoskeleton and ECM that maintains the cell in a state of isometric tension.
The things Ingber studies range from the development of blood vessels to the ways in which "cells respond to signals and coordinate their behaviors to produce tissues with specialized form and function."


As you read Ingber's following explanation of why he thinks this is important, think about the following question: Why does exercise makes your muscles bigger?

We introduced the concept that living cells stabilize their internal cytoskeleton, and control their shape and mechanics, using an architectural system first described by Buckminster Fuller, known as "tensegrity". To approach questions relating to how mechanical distortion of the cell and cytoskeleton influence intracellular biochemistry and pattern formation, we have combined the use of techniques from various fields, including molecular cell biology, mechanical engineering, physics, chemistry, and computer science. This work has led to the identification of mechanical forces and the cytoskeleton as critical cell and developmental regulators, and the discovery that transmembrane integrin receptors which anchor cells to extracellular matrix also mediate mechanotransduction - the process by mechanical signals are converted into an intracellular biochemical response.

Doctors have known for a long time that the body builds itself up according to the way it is used. That's why we prescribe rehab and "pain-free range of motion" exercises for injuries. We knew that injuries heal with less scar tissue if the healing part is (gently) used in its normal range and function. We just didn't know why. Now people like Dr. Ingber are showing why: It's because you are a tensegrity.