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

By Mervyn Waldman

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.