What is Tensegrity??

Buckminster Fuller created the word TENSEGRITY from the words TENSION and INTEGRITY to describe an innovation in architecture. (Fuller 1975) When we think of architecture, we picture things like columns supporting a roof, an I beam supporting a floor or even bricks stacked on other bricks with cement. These components rest upon each other and fight gravity. Tensegrity structures are different in several ways. Most notably, they use components in compression inside a net of continuous tension, in such a way that the compressed members (usually bars or struts) do not touch each other(Gómez-Jáuregui 2010). Kenneth Snelson called it ‘floating compression’.Tensegrity pic

The arches in these photos show just how different these forms of architecture are. The photo in the left corner shows the standard rigid stone arch we normally think of. The photo in the middle shows one of Snelson’s models where wires create tension in a matrix of a very flexible arch.  This concept shouldn’t seem completely strange because we see it in use every day. The spoked wheel of a bicycle or motorcycle is considered a tensegrity system. The thin metal spokes that hold it together are in constant tension between the hub and the rim.  In essence, the hub in the middle is floating in a tension system distributing force. The wagon wheel doesn’t use tension like a bicycle wheel. All of it’s parts must withstand substantial compression. The spokes of the wagon wheel must be thick and rigid like columns of a building to sustain weight. The wagon wheel is subject to the sheering forces that are not present in the tensegrity structure of the bicycle wheel.

This concept applies to biological systems, and that discovery has been revolutionary. It is what keeps a cell from collapsing on itself.  It keeps our joints from being destroyed by our weight.  For centuries, those studying the musculoskeletal system of the body viewed it as a compressive structure like a column or stack of blocks. The old paradigm of the pelvis and sacrum was that the sacrum acted as the keystone to an arch(formed by the ilia of the pelvis) and the legs were like columns supporting this arch.(see illustration above) The compressive structure is built for force in one primary direction. The load is from top to bottom; gravity. It is not built for multidirectional loads. What happens to such a column/arch structure when one column is removed? It collapses. But humans pick one foot up off of the ground in single leg support(1 column) thousands of times a day. Yet the integrity of the SI is unchanged. Levin points out that even in a static situation, the sacrum is not shaped to be a keystone of an arch because it’s anterior(front) surface is much wider than it’s posterior(back) surface. This would cause it to slip forward under the weight of the spine and upper body.(Levin 2007)

If we then look at the tremendous forces placed on the pelvis by an athlete jumping and changing direction, most can agree that the old paradigm is NOT valid. The pelvis(like the spine and the rest of the body) is a tensegrity system where forces are attenuated and sheering forces are minimized. The sacrum should be viewed like the hub of the bicycle wheel. It is floating with ligamentous tension placed on it from multiple directions. (Grant 1952; Kapandji 1977, Dijkstra 2007, DonTigny 2007).The shape of the pelvis(or the spine or shoulder etc) can deform to meet the demands placed on it. Shock can be distributed throughout the system.

Tensegrities allow for flexibility and resilience to the dynamic stress our bodies deal with throughout the day to run or twist or pull or even walk.  Those forces are spread through the musculoskeletal system(especially by the fascia).  But that amazing ability to instantaneously distribute forces throughout the structure also means components can be strained (or irritated) far from the site where the force (or problem) originated.  And that fascia that transmits force through out the body is also loaded with nerve endings that detect tension, compression and the chemical changes that accompany inflammation. The nervous system response to noxious incoming information is often a protective reflex causing muscle guarding or inhibition that causes symptoms. For treatment of pain, this makes assessing the whole body, rather than just the painful region, pivotal for treatment to work.

Even the therapist who has never heard of this concept of tensegrity still makes use of it. Muscles don’t push, they pull. That means they are dynamic components to create ‘tension’. So if the therapist has ever used stabilization exercise to aid lumbar pain or trained an inhibited gluteus maximus(gluteal amnesia) for back, piriformis or hamstring symptoms, he has tried to address tensegrity.

Understanding the existence of tensegrity gives the manual therapist two things that will help him with his patients:

  1. Forces are distributed though the structure. A dysfunction in one area that prevents normal motion will also cause forces to be distributed abnormally somewhere else. The symptoms are often at this overloaded tissue away from the dysfunction. The therapist must find and treat the dysfunction, NOT assume it is in the area of the pain symptom.
  2. Since forces are distributed in many directions, a dysfunction and the compensatory movement patterns it causes may lead to other dysfunctions. The therapist must find and treat the most important dysfunction(also called the area of greatest restriction-AGR, or key lesion) and re-assess the patient to see if treatment affected the AGR and to see if there are other significant dysfunctions.

 

For more information as to tensegrity’s application to the musculoskeletal system see Ed Stiles D.O. or Stephen Levin M.D.  For its ramifications at a cellular and disease level, see the work of Harvard professor Donald Ingber M.D. PhD .

 

 

Dijkstra PF. 2007. In Movement, Stability and Lumbopelvic Pain,  Vleeming, moody, Stoeckhart, Eds. Churchill Livingstone, Edinburgh

DonTigny RL 2007. In Movement, Stability and Lumbopelvic  Pain, Vleeming, Moody, Stoeckhart Eds., Churchill Livingstone, Edinburgh

Fuller RB. 1975. Synergetics. New York: McMillian. 314-431 p.

Gómez-Jáuregui, V (2010). Tensegrity Structures and their Application to Architecture. Servicio de Publicaciones Universidad de Cantabria, p.19.

Grant JCB. 1952. A Method of Anatomy. Baltimore: Williams and Wilkins.

Kapandji IA. 1977. The Physiology of the Joints. Honore LH, translator.

Levin SM. Chapter 15 in Movement, Stability & Lumbopelvic Pain, Churchill Livingstone 2007. Vleeming, Mooney, Stoeckart eds.

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