Howard: Fascia is a fascinating subject, particularly in light of the concept of the body being a self supporting tensegrity system. Tensegrity structures require CONTINUOUS tension networks (fascia, muscle, tendons and ligaments) and DISCONTINUOUS compression components (osseous structures of the skeleton). When tension within the fascia is continually and uniformily applied through the entire network, the body is capable of being a self supportive structure. Many fascia experts assert that the fascia is a continuous structure from the head to the feet. Because of its continuous nature, tension can be applied over the entire system when the windlass winds, and it would appear beneficial for posture in two fashions; overall fascial tightening for improved postural support and that normal sagittal plane dorsiflexion is occurring at the 1st MTP joint allowing normal forward progression. It completely integrates with Grecovetsky’s spinal engine process, as the same tension-compression, support network is synergestic with an energy storage, energy return gait machine.
Robert: I'm probably being grossly simplistic here but If I took a cadaver, stood it up, and dorsiflexed the big toe, it will still probably fall over. Or, better example, if I shot someone full of muscle relaxant and asked them to stand, the fascia / tensegrity won't hold them upright. When we use Botox to chill out a hypertonic Triceps surae group in a CP patient, the muscle relaxes and allows greater dorsiflexion, the fascia has not changed length, but the function has.Howard: By the same logic, if you removed their fascia, and the muscles still functioned (quite the hypothetical).....they would fall over as well. Think of the materials used to make a kite. The plastic covering, balsa wood, etc won't be stable enough to fly until a piece of string is added bowing the balsa wood and adding tension plastic covering and the system as a whole. It then becomes stable enough to fly as long as the tension remains continuous. As muscles press against fascia, they promote tension. It is the combination which allows for support and balance.
Eric: The body is not a tensegrity structure because we do have continuous compression components. The leg bone is connected to the thigh bone....Howard: The last time I looked, the thigh and leg are separated by a joint at the knee, as are the hip and thigh, and ankle and foot. And, these bones would be loose and unstable without the accompanying soft tissues arranged as a continuous tension network.
Kevin: The body can't be a tensegrity structure since a true tensegrity structure does not have compression forces between its structural elements. The last time I checked, the hip, knee, ankle, subtalar, midtarsal joint and first metatarsophalangeal joint all had compression forces between their osseous structural elements. As soon as there are compression forces within the joints of the body, then the body becomes a non-tensegrity structure.Howard: When trying to apply engineering principles to a biologic structure, there is going to be some distortion of the purest of these (engineering) principles to fit what is actually (biologically) present. That neither makes the body nor the principle incorrect. There is clearly a combination of tension/compression occurring in the human structure, and to my way of understanding, tensegrity-esque seems to make the most sense. I fully realize that we are not an absolute anything, so it is easy to find fault and be critical of any of these explanations. However, that does not render any of these "wrong", just that we have yet to develop a single method to describe the body's structural integration. Being able to poke a hole in one aspect does not make tension/compression any less valuable in helping to understand how the body functions. Recognizing the roll of the fascia as a broad based tension band does add to the discussion in a meaningful way, and this was the purpose of my comments.Kevin, I do appreciate your remarks about tension across joints negating the idea that the body could be a tensegrity structure. Many years ago, Steven Levin, an orthopedic surgeon introduced me to the tensegrity concept. He was intrigued by these principles when he realized that after a major knee trauma, once the ligaments of this joint were repaired, and then adequately tightened, the knee joint SEPARATED. He recognized that as tension was applied across the joint surface, the dynamics entirely changed. So, if one were to measure the tension across any joint, it must either be opened or somehow invaded....and this may change the ability to measure the tension influence across these surfaces. We certainly see this on x-ray...that spaces exist between joint surfaces in weight bearing attitudes. I am quite sure that there are other explanations for this phenomena....and I look forward to hearing them.
Kevin: I think the concept of tensegrity is important for the podiatrist and clinician to understand since I believe, as you do, that the mechanical interactions between tension and compression forces within the locomotor apparatus of the bipedal human is critical to allow normal gait function to occur. Is the body a "tensegrity structure" in the strict definition of "tensegrity"? No. By the strict definition of tensegrity, since there are compression forces between the osseous structural components at the joints of the body and there significant bending moments within these osseous structural components during weightbearing activities, the rules of tensegrity are violated within the structure of the human body.However, your term "tensegrity-esque" may be a better one that shows that the body isn't exactly a tensegrity structure but still allows the clinician to understand how important the mechanical interactions between the compression-bearing elements and tension-bearing elements are within the body.
Certainly, we wouldn't have osteoarthritis (OA) developing in the knee joint as individuals age if compression forces didn't exist between the femur and tibia during weightbearing activities. However, without the tensile forces from the meniscal ligaments that restrain the medial and lateral meniscus in their proper positions within the knee joint during these weightbearing activities, knee joint OA would occur at a much earlier age in an individual.
Therefore, the human body does rely on a remarkable balance between compression forces and tensile forces in order to accomplish its daily weightbearing tasks both smoothly and efficiently with little damage to its structural components. Is this tensegrity at work? No. But certainly the principles of tensegrity can be used to better understand how these balancing of compression and tension forces may occur in a harmonious fashion within the human body.
Finis
The cast of characters:
- Kevin A. Kirby, DPM, Adjunct Associate Professor, Department of Applied Biomechanics, California School of Podiatric Medicine at Samuel Merritt College
- Howard Dananberg, J DPM, Bedford Podiatry Group, Eastman Ave, Bedford, NH
- Eric Arthur Fuller, DPM, Berkeley and Oakland, CA
- Robert Isaacs, BSc, MSChP, specialist in Paediatric Biomechanics (children's feet). Writes a column on biomechanics for "Podiatry Now", the journal for the Society of Chiropodists and Podiatrists.
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