ACS > ACS POSTS > Tensegrity: an osteopathic journey into structure-function 2 – part two

Tensegrity: an osteopathic journey into structure-function 2 – part two

By Mervyn Waldman

Given that ASOMI College of Sciences is engaged with issues concerning health and, more precisely, osteopathy; ACS recommends the adaptation of the second part of the scientific paper on tensegrity by Mervyn Waldman, a world-famous osteopath and the current president of the Institute of Classical Osteopathy.

The second part of this article on tensegrity talks about the skeleton, cytoskeleton and the fascia.

In case you missed it, click here for the first part of the article. And, if you already have finished reading the second part, please click here for the third and the last part of this article.

From Skeleton to Cytoskeleton

What does tensegrity have to do with the human body? The principles of tensegrity essentially apply to every detectable size scale in the body. At the macroscopic level, the 206 bones that constitute our skeleton are pulled up against the force of gravity and stabilized in a vertical form by the pull of tensile muscles, tendons, and ligaments (Similar to the cables in Snelson’s sculptures; see Fig. 1).

In other words, in the complex tensegrity structure inside every one of us, bones are the compression struts, and muscles, tendons, and ligaments are the tension-bearing members. At the other end of the scale, proteins and further key molecules in the body stabilize themselves also through the principles of tensegrity.

Very simply, the transmission of tension through a tensegrity array provides a means of distributing forces to all interconnected elements to the couple, or “tune,” the whole system mechanically as one.

For example, changing muscle tone would alter the body posture, from recumbent to standing. Once the tone is set, no further muscle activity is necessary to maintain that posture, as the truss i.e., the supporting framework, is stable. For instance, during quiet standing, no additional muscle contraction would be necessary, and the EMG would not record any significant activity.

Muscles act in unison, as they are the tension elements of the truss.

Loads applied at a point, for example, the sesamoid bones under the first metatarsal, distribute their load through the tension system and compression structure of the body, just as the point of contact of a wire wheel distributes its load through the spokes and rim. There is instant communication among all the cells by force transduction. The small bones of the hands and feet are part of the total system and function as truss members. The compression loads on joints transmit through tension in the soft tissues. Only tension and compression exist in the system and there is neither shear nor moments.

As loads are applied to the system, the strength increases. Muscles become stronger as they contract, and bones become denser and stronger as loads are applied.

Compression elements “float” in the interstices of tension wires. It is rigid, strong, lightweight, and omnidirectional. The tower functions as a column but does not depend on gravity to hold it together. It works equally well as a beam and all the same, elements that are under tension or compression remain under pure stress or pressing with no joint moments, no matter the direction. All elements instantly respond by changing position and a new and stable posture is immediately assumed (if and when efficient proprioception is enabled).

A change of tension anywhere within the system is instantly signaled to everywhere else in the body and there is a total body response by mechanical transduction. The structure works equally well right side up, upside down, in sea, land, air, or space.

foto interna art44 pt2
Tensegrity counters the notion that the skeleton provides a frame for the soft tissues to hang upon. Instead of that, tensegrity structures are integrated, pre-tensioned (self-tensioned), continuous myofascial networks with floating, containing discontinuous compression struts (skeleton). A rigid column needs to be heavy enough to support the incumbent load above. Internal shears forces are created by the weight of the structure, which in turn would be destabilizing. For keeping keep the structure intact, energy would be required in large amounts. Humans are omnidirectional which means that they are capable of adjusting to every direction, as are all biological organisms, so that the tension elements function at all times in tension regardless of the direction of applied force, while the compression elements in biological structures “float” in a tension network. Biologic structures and Sharkey’s findings Ligaments and fascia, bones, and cartilage would do little to support our upright forms if not for the collective activity of an integrated myofascial system. The latter is made up of surrounding tension-generating muscles and tension-resisting tendons, ligaments and fascia, bones, and cartilage. Bone brittleness is approximately the same in all animals. Otherwise, animals bigger than a lion such as horses would break and fracture their bones when running or jumping on their slim limbs. Working elastically at strains around a thousand times higher than strains that ordinary technological solids can withstand, demonstrates that biological tissues behave differently from non-biologic materials. Biologic tissues, including muscles and fascia, have nonlinear stress/strain curves. Sharkey (2012) provided fresh frozen cadaver images of the fascia profunda at the macro level reflecting and creating a body-wide framework or network. This structure can change or maintain shape and form within a fluid base allowing deformation followed by a return to its original state, whilst keeping volume. This creates a stable, yet flexible environment necessary for the fascia to act as a medium for force transmission. This new model for biologic structures based on the concept of tensegrity identifies the fascia as the tensional, continuous member. In a tensegrity continuous tensile forces (from the myofascial tissue) provide an “ocean” within which the struts float (in the human body these could be the bones that are not continuous with each other and they do not transmit compression directly onto each other.). The tensional members are continuous and distribute their tension load directly to all other tensional parts. Tensegrity structures and tissue stress Tensegrity structures are triangulated allowing force transmission in multiple dimensions. This architectural system for the structural organization provides a mechanism to physically integrate a part and whole. Every time we move our arms, the muscles contract, the bones compress, and the skin stretches without any irreversible injury. This is made possible because most of the load-bearing elements of the discrete cellular and extracellular matrix networks that comprise living tissues rearrange in response to stress. They then return to their original position when they are released, as is observed in all tensegrities. If stresses are excessive or sustained, then our bodies remodel themselves through “mechanochemistry”, i.e., force-dependent changes in molecular polymerization-depolymerization dynamics or alterations of molecular biochemistry. In this way, tensegrity governs how mechanical forces influence the form and function of the living cells that inhabit all of our tissues. The example of knee joint Most readers will be familiar with x-rays of the knee joint. Even while standing the space between the femur and tibia is obvious. This space hints at the special architecture of the human form. It is still currently taught that during running, cartilage tissues absorb the crushing forces of three to six times our body weight compressing and crashing down on our joints. However, not even NASA has invented a material that could do such a job. It is taught that cartilage absorbs crushing forces repeatedly, over hours of impact (six times our body weight crushing down on our joints) such as when running a marathon. The knee joints are frictionless. This tells us the cartilage is not compressed and therefore has no need to absorb the impact. That is, not in a healthy joint supported by healthy tissue as opposed to an unhealthy one where compressive forces damage the cartilage and bone. The space witnessed at joints is a result of the bones floating in the tensional connective tissues. Bones are not meant to touch and when they do (and they sometimes do) this is a reflection of something having gone wrong. In effect, the system is not performing, as it should. What holds the body up? Imagine the body is standing upright, and the skin and soft tissues (muscles, fascia, viscera, and all) were to disappear. What would happen to the skeletal system? Of course, it would crash to the floor. But what if all the bones were removed leaving only the soft tissues? Again it would end as a soft heap on the floor. This begs the question, “what is holding the body up.” In such a scenario it is easy to conclude that it is the relationship between the soft and harder tissues continuously working that provide humans with what we call “lift.” It is exactly this lift that protects the integrity of the joint space. This description supports the more recently accepted image of a continuous tissue, ubiquitous in nature, connecting left to right, front to back, top to bottom, embracing and permeating the entire body. These mesenchyme-derived connective tissues provide a body-wide network of communication. The visceral organs integrate structurally and physiologically into this system. There are no limb segment boundaries and the smaller bones and joints of the hands and feet fully integrate into the tensegrity model. Spine as a tensegrity structure The spine is a tensegrity structure that integrates with the limbs, head, and tail and also to the visceral system. A change of tension anywhere within the system, such as the mid-back, is instantly signaled to everywhere else in the body chemically and mechanically. There is a total body response by mechanical transduction i.e., the molecular mechanism by which cells sense and respond to mechanical stress. Dictated by changes in movement and posture, mechanical forces, comprising of tension and compression, may provide a means of communication resulting in connective tissue signaling and that the fascia translates these signals into a whole-body communication system. Such connective tissue signaling would be affected by changes in posture and motion and may lose mobility in pathological conditions or when experiencing pain. Due to the intrinsic relationship that connective tissue has with, among others, the lungs, intestines, heart, spinal cord, and brain, connective tissue signaling may have a reciprocal influence on the functions, normal or pathological, of a wide spectrum of organ systems. Sensory neural fibers have been identified within the fascia utilizing unique staining techniques coupled with electron microscopy which suggests that fascia contributes to proprioception and nociception. Fascia also has considerably more sensory nerves when compared to muscle including Golgi, Paccini, and Ruffini endings. These include a large number of microscopic unmyelinated ‘free’ nerve endings. These nerve endings are found in a near-ubiquitous manner in fascial tissues including periosteum, endomysial and perimysial layers, and in visceral connective tissues. Click here for the third part of the article including the bibliography.
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