Friday, July 27, 2012

Fascia Therapy --- Sports Injury and Rehabilitation: Acute or Chronic Swelling

This post is intended to complement my earlier post on Multiple Sclerosis (MS) and the multi-modal approach of the Fascia Therapy (formerly the Activ8 System) to address the common symptomatic challenge of lymphedema and chronic inflammation in the lower leg as well as swelling and edema as a result of sports injury.  The multi-modal approach is designed to integrate complimentary interventions in an effort to maximize the potential impact as well as allow for customized modification and adjustment to ever-changing systemic and mechanical environments.  

Lymphedema is a chronic condition that is characterized by the inability for the lymphatic system to remove fluid from the lower extremities in conditions such as MS and can also be the result of acute injury which results in a level of edema accumulating that the lymph system is unable to remove efficiently.  In chronic conditions such as MS, this symptom can be uncomfortable and even incapacitating...therefore focused intervention is not only a productive long-term objective, but it may also be a very real and critical short-term goal as well.  With respect to sports / acute injury (ankle sprain, calf muscle strain, etc...) swelling is a normal part of the healing process, however it is essentially a "supercompensatory" mechanism where there is often times and inordinate amount of fluid that is drawn to the area (capillary flow, osmosis, etc..). This can sometimes create additional levels of pain and, more importantly, affect the ability to implement more aggressive rehabilitative protocols.  Further, the large amount of local fluid draw can also leave the surrounding tissue in some level of nutritional and oxygen deficit which lead to secondary challenges.

The specific multi-modal approach used to address inflammation in the 
Silicone Stress Transfer Mediums
Fascia Therapy concept is the combination of therapeutic taping (Kinesiotaping) and Trans-Fascial Viscoelastic Stimulation (TFVES). Using various stress-transfer mediums, the practitioner is able to access the connective tissue / fascia at all levels including the very deepest visceral / core level.  TFVES is a very comprehensive set of skills, applications, guidelines, and targets that require an extensive process of learning and development...however the overwhelming scientific and clinical evidence shows that is produces extraordinary benefit and contribution to the improvement of connective tissue strength, health, integrity, and homeostasis...therefore reducing fascial dysfunction and the reduction of abnormal pain signalling.  In addition to the enormous systemic benefit, there is also a very significant improvement in the overall health, strength, and integrity of the connective tissue system which contributes to structural integrity and therefore improves functional performance and the reduction in rate of re-injury.  More importantly, and most relevant to this specific application, TFVES is a very effective tool for the manual movement of fluid.  In other words, the very specific loading properties (guidelines) and the specific viscoelastic characteristics of the stress stransfer medium enable the practitioner to access fluids at the deepest level...which are typically unaccessible using the hands alone.  This powerful tool facilitates very rapid and effective movement of the interstitial fluid through the lymphatic system and therefore replenishes the entire system by flushing stagnant fluid and stimulating return of new nutrient rich fluid. 

Kinesiotaping is a specifc technique that has been widely used since the early 1970's in the rehabilitation setting in Japan but since the 80's has risen to become relatively mainstream.  Its function / implementation serves 2 essential purposes:  1) facilitate movement performance, 2) facilitate fluid flow and systemic homeostasis.  For this particular post, it is being implemented as a facilitator of lymphatic drainage and interstitial flow.  It is applied using the lymphatic correction technique (Kase) and is channelled to another part of the system that is functioning properly...therefore application location is highly variable depending on the individual case.  In combination with the TFVES technique, fluid flow is effectively channelled away and therefore facilitating the return of nutrients back into the system as well as the proper elimination of waste and toxic by-product.  I recommend that you refer to my two previous posts that outline the diverse potential of the systemic implications of the use of Kinesiotape.  

Inflammation of the Lower Leg:

 Patient is positioned with the knee in extension and the foot in dorsiflexion.  

Working from proximal to distal, the first fan tape is placed on the posterior medial aspect of the knee.  

Lay down the strips over the area of edema with approximately 25% tension.  The last 2 inches of the strip should be laid down without any tension. 

The second fan tape is placed just superior to the first (or depending on the specific case, can be placed on the lateral aspect of the knee).  

Angle the strips inferiorly and form a criss-cross pattern over the area of edema.  

Initiate glue activation by rubbing the entire application vigorously (but carefully).  Glue activation should be done before any movement is initiated. 

Completed Application

 TFVES application with Kinesiotape:

As previously mentioned, the TFVES technique has very specific guidelines and movement / loading properties that require some expanded and enhanced demonstration and training in order for it to be effective (SEE FASCIA THERAPY Sports Injury Protocols and Courses).  However, I will provide a demonstration that is to serve for illustration purposes only.  

Starting distally, the stress transfer medium is slowly loaded (pressed) into the posterior leg. 


The cylinder is then rolled until it reaches the mid-palm. The pressure is released slightly, and the action begins again from the starting position.

The same guidelines should be applied along the entire length of the lower leg in separate sections (mid-calf, proximal calf) until the proximal end of the application is reached.

In summary, this particular multi-modal intervention has shown significant results in our MS patients as well as the treatment in the healthy individual / athlete. Not only is there a visible and tangible improvement, the patients report overall relaxation and a slight increase in function and performance. These initial reports conclude that further implementation of the multi-modal approach is indicated. Future posts will demonstrate the diversity of this intervention over a wide spectrum of acute and chronic conditions. In addition, the Fascia Therapy Sports Injury and Rehabilitation protocols will further consilidate and formalize specific taping applications and the respective Fascia Therapy techniques.


Friday, July 20, 2012

The 4 Diaphragms

My recent look into the work of Leon Chaitow and the subsequent "dip" into respiratory mechanics resulted in an exponential growth in understanding (and appreciation) of the continuity of the human organism...more specifically, each and every action, however small, is intimately linked with the entire organism.  To be precise, it is literally impossible to "dissect" unique movements / functions / systemic actions out from the is quite frankly unrealistic to remain adhered to this simplistic idea. 
There are many different examples that can be brought forward and examined, however I think it would be more productive to choose an example that will resonate with the largest number of other words, something that can be understood immediately regardless of their "anatomical competence".  

In a previous post on respiratory mechanics I discussed the effects of dysfunctional breathing patterns on the brain.  This is also an example of the intimate relationship between structural distortion and systemic performance...however it relates to the brain, which remains a relatively "mystical" organ that we still do not completely understand.  This post is intended to demonstrate the pure mechanics of breathing and its relative complexity.  In addition, it becomes very clear that breathing isn't as simplistic as we like to think...or in some cases, not as simple as some people would like you to believe.  The reality is that respiration is a multi-faceted function that engages all of the architectural components (bones, tendons, ligaments, muscles, fascia) of the body as well as the metabolic / systemic components (lungs, organs, brain).  This is best understood through the fundamental examination of the 4 diaphragms of the body.

The 4 Diaphragms:

1)  Cranial Diaphragm 
 It is well documented in Osteopathic studies that the central nervous system (CNS) has a certain "rhythmical motion" to it.  In other words, it has life and actually pulsates as a means to mobilze Cerebral Spinal Fluid (CSF).   This rhythmical movement is said to be intimately linked to cardiac rhythm and is profoundly affected by breathing patterns.  The cranial diaphragm is composed of differentiated connective tissues in the skull called the Falx Cerebrii and the Tentorum Cerebelli.

2) Cervical Diaphragm
The cervical diaphragm is composed of the tongue, the muscles of the hyoid bone, and scalene muscles.

3) Thoracic Diaphragm 
The most common and well-known diaphragm which separates the thoracic cage from the abdomen.

4) Pelvic Diaphragm
Found on the pelvic floor, it links the sacrum to the pelvis and is essentially a large "sheet" of specific muscles. 

In the above video, the 4 diaphragms work together in unison to contribute to the respiratory rythym which is fundamentally important for the proper function of the central nervous system, circulatory system, and critical metabolic / systemic functions.  This very informative video brings into focus the fundamental concept of fascial articulations as a valid consdieration as a true joint. The mechanical movement of the thoracic diaphragm mobilizes the abdominal viscera and therefore requires that the "disconnecting" lubricating physiological appearance of connective tissue is in place and healthy.

In addition, the mechanics of breathing require proper movement and passive excursion of the entire musculoskeletal system (elasticity of the ribcage, mobility of the sacrum between the iliac bones, division and segmentation of the clavicles from the first 3 ribs.  In addition, the impact of the thoracic diaphragm on the viscera stimulates and activates the pelvic diaphragm below.

The video essentially speaks for itself, therefore long paragraphs and a high "word count" isn't necessary.  However, I hope the overall message is relatively clear:  there is no possible way to disentangle the systemic from the architectural.  They are a symbiotic entity and therefore, by definition, depend on each other to ensure the homeostasis of the organism.  

I anticipate more informative posts as my look into respiratory mechanics continues and evolves...please stay tuned!


Forced Perspectives In Rehabilitation

Considering the two previous posts were relatively "heavy" in nature and content, I thought it would be appropriate to put a slightly "lighter spin"into this post.  Forced perspective is something that I have always been aware of, but it is only recently clicked on how it actually applies in everyday life...and of course, rehabilitation. 

The image to the left is one of many examples of Forced Perspective Photos.  What is forced perspective?  It's quite simply examples of how reality can sometimes easily be distorted depending on "how you are looking at it".  In photography, this distortion results in some fabulously creative images...however, in the field of rehabilitation, the results are not as pleasant.  Distorted perspective leads to inefficient strategies and therefore unproductive results.  

With forced perspective photography, we KNOW that it is all a trick...whereas in the rehabilitation community it seems like most are convinced that their perspective is the actual reality.  Using the clever image to the left, if this was your only perspective, you would be lead to believe that while two men are enjoying a pleasant day in the city, another man is dangling precariously in the air.  Which is the reality and which is the distortion?  I suppose it depends on who you ask.  In the healthcare industry, the idea of "it depends on who you ask" is an unfortunate reality...however, if there is focused effort to step back and gain some additional perspective, the inevitable product would be an improvement in the desired goal and result. 

In the spirit of keeping this a "zero-calorie" post, I will use a very simple (yet organic) example of how perspective plays a fundamental role in the implementation of successful rehabilitation protocols. 

 Nothing could be simpler than a good old's round, has a skin, and is filled with delicious pulp.  Although this is in fact true, the paradox is that the information it provides is quite complex and comprehensive.  For the sake of efficiency, I will formulate this idea in a conceptual manner...thus it will simply be a question of importing this concept to your existing reality.  Consider the skin of the orange (the bright orange outer layer) as analogous to human skin, the dull orange underlayer as the subcutaneous tissue, the watery orange pulp as the muscle, and the "stringy" portions that seperate the orange segments as the connective tissue. 

Fundamental Perspective Question #1  What provides the structural stability within this organic system?  It seems strange to ask such a complex question about a simple fruit...but the conceptual message is quite important.  Is it the pulp itself that supplies the compressional integrity of the fruit or is it the "connective tissue" within?  Further, is it a combination of both...with the pulp delivering the compressional stability and the rest supplying the tensional support?  If you ask this question in relation to the human organism, the flood of new questions would be quite powerful.

   Fundamental Perspective Question #2:  How is the internal architecture organized? In the case of our friendly orange,  your perspective would be dependant on whether you sliced it axially or transversely.  When most of us think of oranges, we perceive them in the classic "transverse" way...nice triangular pieces housed nicely within the soft skin of the orange.  But the "axial" slice is obviously part of the same orange, but it presents a very different understanding of how the orange os actually organized.  It is a hslf-circle of pulp secured to the center via a thickened extension of the outer layer.                                                                      
These questions and analysis may seem trivial, however the conceptual message should once again be understood:  If a simple orange can demonstrate such vast architectural differences depending on perspective, imagine how important perspective becomes when analyzing the human organism. This is precisely why even professionals gets confused when presented with cross-sectional images...the anatomical perspective changes completely and leaves them confused as to "what is what". 


 Fundamental Perspective Question #3:  Where does the skin end and the pulp begin?  This is perhaps the most important concept to integrate.  Is the orange the sum of an outer skin, an inner skin, and pulp...or is it one complete entity.  My perspective should be obvious...the orange (and therefore the human organism) is a singular entity that is characterized by the differentiation of tissue types.  Each differentiated tissue is intimately connected to the other and function in complete inison.  In addition, integrity of the whole organism is dependant on the balance and stability of the combined tensional and compressional forces within. 

In summary, I am sure you have never devoted as much analysis to a fruit...however, examples of the complexity of life are everywhere...even on the kitchen table.  It is important to realize and understand that it is impossible to import simplistic strategies into complex systems...which is the unfortunate reality in many cases with respect to current healthcare.  Ido not pretend to hold the answers to the complexity of the human body...but gaining proper perspective is most certainly one of the first steps towards responsible and effective strategies.

I will end this post with some more cool forced perspective photos...they are not only fun, they remind us to always think about what we ware looking at!  Cheers!


Wednesday, July 18, 2012

The Cranial Vault

Once again, the work of Graham Scarr D.O.  This is an amazing look into the tensegral properties of the human skull and therefore providing a greater understanding of the mechanics of the cranium.  As usual...a very insightful perspective!


 A model of the cranial vault as a tensegrity structure,
and its significance to normal and abnormal cranial development.
This is a modified version of a paper published in the:
International Journal of Osteopathic Medicine 2008;11:80-89
Traditional views of the human cranial vault are facing challenges as researchers find that the complex details of its development do not always match previous opinions that it is a relatively passive structure. In particular, that stability of the vault is dependant on an underlying brain; and sutural patency merely facilitates cranial expansion. The influence of mechanical forces on the development and maintenance of cranial sutures is well-established, but the details of how they regulate the balance between sutural patency and fusion remain unclear. Previous research shows that mechanical tensional forces can influence intracellular chemical signalling cascades and switch cell function; and that tensional forces within the dura mater affect cell populations within the suture and cause fusion.
Understanding the developmental mechanisms is considered important to the prevention and treatment of premature sutural fusion - synostosis - which causes skull deformity in approximately 0.05% of live births. In addition, the physiological processes underlying deformational plagiocephaly and the maintenance of sutural patency beyond early childhood require further elucidation.
Using a disarticulated plastic replica of an adult human skull, a model of the cranial vault as a tensegrity structure which could address some of these issues is presented.
The tensegrity model is a novel approach for understanding how the cranial vault could retain its stability without relying on an expansive force from an underlying brain, a position currently unresolved. Tensional forces in the dura mater have the effect of pushing the bones apart, whilst at the same time integrating them into a single functional unit. Sutural patency depends on the separation of cranial bones throughout normal development, and the model describes how tension in the dura mater achieves this, and influences sutural phenotype. Cells of the dura mater respond to brain expansion and influence bone growth, allowing the cranium to match the spatial requirements of the developing brain, whilst remaining one step ahead and retaining a certain amount of autonomy. The model is compatible with current understandings of normal and abnormal cranial physiology, and has a contribution to make to a hierarchical systems approach to whole body biomechanics.

For many years it has been widely accepted that the cranial vault expands through an outward pushing pressure from the growing brain, with the sutures merely accommodating its growth and fusing in the third decade of life.1,2 However, recent data suggests that daily brain growth is too small to induce sutural osteogenesis, and that in any case, substantial growth is over before the completion of sutural growth.3,4,5,6 Human facial sutures normally remain patent until at least the seventh or eighth decade, whereas the timing of sutural fusion in the cranial vault is extremely variable and unreliable forensically.7,8 Many factors affect cranial enlargement - some are genetic while others are epigenetic.
Understanding the developmental mechanisms of the cranium is considered important to the prevention and treatment of the pathologies affecting the neonatal cranium. Craniosynostosis is the premature fusion of one or more of the cranial sutures resulting in skull deformity, and occurs in roughly 1 in 2000 live births.4 It may be associated with specific genetic syndromes or occur sporadically, and any cranial suture may be involved, although with differing frequencies.2,9,10 Premature fusion results in arrested bone growth perpendicular to the synostosed suture, with subsequent abnormal compensatory growth in the patent sutures.1,2,9,11 Another skull deformity, not due to synostosis, is positional moulding or deformational plagiocephaly. When present at birth it is the result of in-utero or intrapartum molding, often associated with multiple births, forceps or vacuum-assisted delivery; or post-natally resulting from a static supine positioning.12 One of the difficulties during this period is differentiating premature fusion from abnormal moulding. By the time children are diagnosed with craniosynostosis, the suture has already fused and the associated dysmorphology well established. Surgical intervention may then be necessary for neurological or cosmetic reasons.
The adult skeleton is mostly capable of healing defects and deficiencies via the formation of new bone. However, while children under the age of 2 years maintain the capacity to heal large calvarial defects, adults are incapable of healing the smallest of injuries. The coordinating mechanisms behind normal and abnormal development are currently incomplete,10,13 and the model to follow presents a novel approach to furthering our understanding of the processes involved. Although many readers will have an extensive knowledge of the cranium, others may be unfamiliar with the details which underlie the significance of this model, and a brief overview follows. 

The Cranial Vault or calvarium:
  The cranial vault, or calvarium, surrounds and encloses the brain, and is formed from several plates of bone which meet at sutural joints, unique to the skull, and which display a variety of morphologies specific to each suture.2,7,11,14,15 The high compressive and tensile strength of bone provides mechanical protection for the underlying brain, while the sutural joints provide a soft interface and accommodate brain growth.10 The vault bones are the frontal, parietals and upper parts of the occiput, temporals and sphenoid. Inferior to the vault is the cranial base, or chondrocranium, which is made up of the lower parts of the occiput and temporals, the ethmoid and the majority of the sphenoid. In the embryo, the vault bones develop through ossification of the ectomeninx - the outer membranous layer surrounding the brain; while the cranial  base  develops  through  an  additional  cartilaginous stage,2, 16 the significance of which will be discussed later (Individual bones spanning both regions fuse at a later stage). Enlargement of the neurocranium occurs through ossification of sutural mesenchyme at the bone edges, and an increase in bone growth around their perimeters.1,15 During this process, the ectomeninx becomes separated by the intervening bones into an outer periosteim and internal dura mater. By the time of full term birth, the growth of the different bones has progressed sufficiently so that they are in close apposition, only separated by the sutures which intersect at the fontanees (Figure 1). At full-term birth, sutural bone growth is progressing at about 100 microns/day, but this rate rapidly decreases after this. Maintenance of sutural patency is essential throughout for normal development of the brain and craniofacial features.2,4,10 The brain has usually reached adult size by the age of 7 years but the sutures normally persist long after this - until at least 20 years of age. Even after this, there is considerable variation in the pattern and timing of sutural fusion in the human adult throughout life.2,7,8,16 Animal sudies of the cranial vault clearly demonstrate sutural patency throughout.2,16

The Dura Mater: The dura mater is the outer one of three membranes surrounding the brain (fig. 2). Its outer surface – the endosteal layer, is loosely attached to most of the inner bone surface, particularly in children, but more firmly attached around the bone margins, the base of the skull and foramen magnum. The inner meningeal layer of the dura mater continues down through the foramen magnum and surrounds the spinal cord as far as the sacrum. This layer also reduplicates inwards as four sheets which partially divide the cranial cavity and unite along the straight sinus - the falx cerebri, falx cerebellum and bilateral tentorium cerebelli.
The internal structure of the dura mater consists of inner and outer elastic networks and integumentary layers, and a collagen layer; although abrupt boundaries between these ‘layers’ cannot be distinguished histologically.17 The collagen layer occupies over 90% of its thickness, with collagen fibres arranged in parallel bundles and differing orientations - varying from highly aligned to apparently random, and arranged in lamellae.18 Typically, with age, the dura mater thickness changes from 0.3 to 0.8 mm.17,18 Collagen has the strongest mechanical properties of the different structural proteins, and fibre orientation has been observed to coincide with the direction of tensile stress.9,18,19,20

The Sutures: Adjacent cranial vault bones are linked through fibrous mesenchymal tissue, referred to as the sutural ligament (fig. 2).15 The two layers which derive from the embryonic ectomeninx – the periosteum and dura mater, continue across the suture, and also unite around the bone edges.15 In the cranial base, ossification occurs through cartilage precursors, some of which fuse together in the foetus or early childhood.
The synchondroses are the intervening cartilages between the bones of the cranial base. The spheno-basilar synchondrosis normally ossifies in the third decade, and the petro-occipital fissure (synchondrosis) in the seventh.21 The cranial base is relatively stable during development, with the greatest size changes taking place in the vault.
Morphogenesis and phenotypic maintenance of the sutures is a result of intrinsic differences within the dura mater.1,5,10,16,20,22 The significant factors in this are cellular differentiation, intercellular signals and mechanical signals.23

(1) Cells of the dura mater beneath the suture undergo epithelial-mesenchymal transitions - a mechanism for diversifying cells found in complex tissues, and migrate into the suture as distinct cell populations.23,24,25 Fibroblast-like cells in the centre produce collagen and maintain suture patency. Those with an osteoblast lineage also produce a collagen matrix, but lead onto bone formation at the suture margins, causing the cranial bones to expand around their perimeters.13 Osteoclast mediated bone resorption may be necessary for changes in the complex morphological characteristics at the sutures edges.26 A complex coupling between fibroblast, osteoblast and osteoclast populations determines the actual position and rate of sutural development.5,10,26,27 In addition, a critical mass of apoptotic cells within the suture is essential to maintaining the balance between sutural patency and new bone formation.10,14

(2) Intercellular signalling influences epithelial cell function through the production and interactions of soluble cytokines such as the ‘fibroblast growth factors’ and ‘transforming growth factors’.23,25 The cells at the approximating edges of the bones, either side of the suture (bone fronts), set up a gradient of growth factor signalling which regulates the sequential gene expression of other cells, and causes changes in the spatial and temporal development of different cell populations.10,13,22,28

(3) Mechanical signals.The morphology of the suture also reflects the intrinsic tensional forces in the dura mater, in the order of nano or pico Newtons.1,3,27,28 Regional differentials in this tension create mechanical stresses which interact and exert their effects on the cells, stimulating them to differentiate and produce different cell populations.4,20,23,27,28 The sensitivity of the cellular cytoskeleton to tensional forces, and the particular pattern of stress application, has been shown to be crucial in determining the cellular response through a process of mechanotransduction.2,28-34 Given that the cytoskeleton is attached to the surrounding extracellular matrix through mechano-receptors in the cell membrane, a mechanical force transfer between them can produce global changes within the cell by altering the cytoskeletal tension. Multiple chemical signalling pathways are activated within the cell as a result, and together with intercellular chemical signals, provides multiplexed switching between different functional states such as differentiation, proliferation and cell death.29,30,32

It is actually not an essential requirement for a spherical tensional structure to be maintained through an expansive force (such as a growing brain) in order to remain stable.3,35 The proposal here is that the calvarium of the neonate could be such a structure which maintains its shape through other mechanisms, being influenced by the expanding brain as a secondary factor.

The concepts of tensegrity have become increasingly recognized over the last thirty years as a model for understanding some of the structural properties of living organisms.29,30,35-42 This appreciation follows from investigations in the 1940s by the sculptor Kenneth Snelson, and the architect Buckminster Fuller, into novel structures in free standing sculpture and building design.35,41 Although  Snelson  actually  discovered the concept, and has used  it  to great effect in his sculptures, it was Fuller who defined the basic geodesic mathematics. The word ‘tensegrity’ is derived from the words ‘tension’ and ‘integrity’ and describes structures which are inherently stable as a result of their particular geometry. 

Fuller found the icsoahedron to be a useful model for describing certain aspects of geodesic geometry - the geodesic dome and tensegrity.35,36 The outstanding feature of geodesic domes is that they have a rigid external frame maintaining their shape, based on a repeating pattern of simple geometry (fig. 3a). In the human body, this type of structure is found in the cytoskeletal cortex of most cells;43 and in the erythrocyte, the geodesic structure is considered a primary contributor to the functionality of its peculiar shape.44

Tensegrity structures have been well described by Ingber in the inner cytoskeletons of cells;29,30 and Levin in the shoulder, pelvis and spine,36-40 suggesting their ubiquity throughout the organism.
In development of the model, the icosahedron is converted into a tensegrity structure by using six new compression members to traverse the inside, connecting opposite vertices and pushing them apart (fig. 3b). Replacing the edges with cables now results in the outside being entirely under isometric tension. The inward pull of the cables is balanced by the outward push of the struts, providing structural integrity so that the compression elements appear to float within the tension network. A load applied to this structure causes a uniform change in tension around all the edges (cables), and distributes compression evenly to the six internal struts, which remain distinct from each other and do not touch.35 (Some of the edges of the geodesic dome (fig. 3a) have disappeared in the transition to tensegrity (fig. 3b) because they now serve no structural purpose and are redundant.) Replacing the straight struts (fig. 3b) with curved ones (fig. 3c) maintains the same stability, but they now surround a central space. In the same way, the curved struts can be replaced with curved plates (not shown) and the structure still retains its inherent stability.

The use of curved struts in tensegrity can be understood through structural hierarchies. In biology, it is common for component structures to be made up of smaller structures, which are themselves made up of still smaller substructures. Structural hierarchies provide a mechanism for efficient packing of components, dissipation of potentially damaging stresses and integration of all parts of the system. Thus, the appearance of curves at one scale are seen to result from interactions of components at a smaller scale, and the forces of tension (attraction) and compression (repulsion) always act in straight lines within them.

The plastic adult skull model illustrated in figures 4 - 7 shows curved plates of cranial bone - representing the compression struts, apparently ‘floating’ in the dura mater - shown here as elastic tension cords. The bones do not make actual contact with each other at any point. As this paper essentially concerns the cranial vault, the facial bones have not been separated. Bones of the cranial base are shown here as part of an overall tensioned structure, in spite of the synchondroses being under a certain amount of compression in vivo. Their development in the early embryo could be part of a tensegrity structure, only changing to compression as the cartilage growth plates replace membrane between the bones. They are shown as they are in order to demonstrate the potential of the tensegrity principle through all stages of cranial development. Substituting the tension cords of these model sutures with a compression union would not alter that principle in the vault. The spheno-basilar synchondrosis (fig 7) has been distracted in order to display the isolation of each bone within the dura mater more clearly. (It also supports the unbalanced weight of the face; but see the additional wire model below.) Internal cranial structures have been omitted for the sake of clarity.
A fundamental characteristic of tensegrity structures is, as Fuller described it, “...continuous tension and discontinuous compression”.35

 These concepts are illustrated in figure 8a which shows a schematic diagram of the bones spread out in two dimensions. The bones are the compression elements which are being pulled by dural tension  (only a small number of tension forces pulling in one general direction are shown in this diagram). Here they remain distinct from each other and do not make contact with each other at any point - ‘discontinuous compression’. This contrasts with figure 8c, which shows the compressive load of a stone wall bearing down through the keystone and both sides of the arch - the compression force here is continuous.

Returning to figure 8a, the tension cords are pulling in different directions, but a resultant tensional force develops (large arrows) which is dependent on the size and direction of the contributing tensions (the ‘parallelogram of forces’ in mechanics terminology). Starting with the left temporal: the tension pulls the left parietal (indirectly here) towards the left temporal in the direction of the resultant force. At the same time, the left parietal is pulling on the right parietal through the same mechanism, and this in turn is pulling on the right temporal. The consequence of all this is brought together in figure 8b, showing the same  bones  arranged  in  a  circular anatomical  sequence,  the  resultant tension pulling on each bone in turn, passing around the circle, and ultimately pulling on itself – ‘continuous tension’. Before running away with thoughts of perpetual motion, it must be pointed out that an equal and opposite tensional force will also be pulling in the opposite direction with the effect of – zero – nothing happens! This same isometric tension is acting across all the sutures in 3 dimensions, and because it is a tensegrity structure, the consequence is that all the tensional forces are balanced, the bones appear to float, and unless acted upon by another force, the structure will remain as it is. The precise placement and directions of the tensions is extremely important if the structure is to maintain itself as described, and is detailed later. While the simple 6-strut model is useful for demonstrating tensegrity, such structures can be made using any number of compression struts from two upwards, with the compression members remaining distinct from each other.45

The model was constructed from a full size plastic adult skull obtained from a medical suppliers and cut into the individual bones using a fine coping saw, with the exceptions of the facial bones which remain as a unit with the sphenoid. Although the intricacies of the serrate sutures could not be followed exactly, comparison with a real bone skull confirmed their essential similarities for the purpose described. Holes drilled at the bone perimeters were threaded with an elastic cord, as used in textile manufacture.The tension cords are positioned so that they illustrate the nature of the tensegrity structure and do not necessarily follow any particular anatomic structure. However, during positioning of the attachment holes, it became apparent that they should be as close to the edge as possible in order for the structure to work effectively. It was also evident that the various curves of the bone edges, in all three dimensions, facilitated a separation of the bones by making alternate attachments between the peaks of opposing bone edge convexities (fig 9a).

One of the difficulties found in constructing this model was the unexpected vault shape changes caused by adjusting individual cord tensions. Tensegrity structures have visco-elastic properties similar to biological structures, and this can cause them to behave unpredictably because of a non-linear relationship between stress and strain.9,35,46 A summary of some of the significant mechanical aspects of tensegrity design and how they apply to the human skull follows:

3.1. Stability
Stability is achieved through the configuration of the whole network, and not because of the individual components. The model describes a mechanism whereby the calvarial shape could be maintained independently of any outward-pushing pressure from the brain within,1-6 a position currently unresolved. The sutures remain under tension (tension being necessary for regulating bone growth), while the bones remain mechanically distinct from the brain, being influenced through cells of the dura mater to expand. It is likely that the vault shape of the early foetus would be reliant on the expanding brain pushing outwards on the ectomeninx,2,4,10 but tensegrity could become a significant factor after 8 weeks, as ossification stiffens the membranous tissue and transfers tensional stresses across the developing bone (fig 8a).23 Chondrification would transform the base into a more 'geodesic dome' structure with greater stability (fig. 3a), and reorient certain vectors of growth influencing the greater expansion of the vault.1,2

During construction of the model, it became evident that it would only work effectively if the tension cords were attached near the edges of the bone. In children, the strongest attachments of the dura mater are also around the bone margins, suggesting that this may be significant and congruent with the mechanism being modelled.20 Continuity of dural tension is thus maintained beneath the bone and may affect intercellular signalling from one side to another. Firmer attachments of dura mater in the centre of adult bone would not affect the tensegrity principle, but implies a change in that signalling, and may influence the lack of bone healing capability in the skull after early childhood.

It must be emphasized that this model describes a structural mechanism which may be functioning in living tissue. It would not work in preserved skulls or cadavers where sutural and dural tissues have lost their elastic resiliency, and the structure becomes fixed under continuous compression (Figure 8c).

3.2. Balance
The tension and compression components are balanced mechanically throughout the entire structure, which will optimize automatically so as to remain inherently stable. The various curves of the bone edges, in all three dimensions, facilitate a separation of the bones through alternate tension attachments between opposing bone edge convexities (fig 9a). The attachments on either side naturally settle along the tension line. Consequently, if those attachments are at the peak of each convexity, the bones will be pushed apart in a direction perpendicular to the tension force, and held there. Directional tensile stresses in the dura mater and collagen fibre orientations have been found.9,18-20 For example, symmetrical fibre orientations in the temporal regions were observed to be 6.3 degrees +/- 0.8 degrees in respect to the sagittal suture.18 At a different size scale, figure 9b demonstrates the same principle in a serrated suture. The serrate sutures increase the surface area between adjacent bones because of their interlocking projections, but the tension attachments holding the bones apart, as described above, would also decrease the potential for sutural compression in this model. [Since the publication of this paper, it has been shown that tensioned collagen fibres within the sutures are aligned such that they resist compression, as described here. Jasinoski SC, Reddy BD, Louw KK, Chinsamy A. 2010 Mechanics of cranial sutures using the finite element method. Journal of Biomechanics 43:3104-3111.]  In figures 9a and 9b the tension cords are causing the bones to be pushed apart. This is strange behaviour indeed, considering that tension is generally noted for pulling, and not pushing. It underlines how the non-linear relationship between stress and strain in tensegrity and biological structures could be brought about. Conflicting forces resolve themselves by taking the paths of least resistance, eventually settling into a stable and balanced state of minimal energy. However, a living organism has a field of force dynamics which are in a continuous state of flux, so that stability and balance are constantly changing (if that is not a contradiction in terms).32,47,48

Cells of the dura mater respond to brain expansion and influence bone growth, allowing the cranium to match the spatial requirements of the developing brain, whilst remaining one step ahead and retaining a certain autonomy.1-6 This position renders the vault more adaptable to other functional requirements, such as the demands of external musculo-tendinous and fascial attachments.7,21A tensegrity cranium balances its stability through all stages of development, by allowing small and incremental changes compatible with the mechanical demands of all connected structures.

3.3. Energetically efficient
Energetically efficient means it has maximum stability for a given mass of material. The geodesic dome can enclose a greater volume for minimal surface area, with less material than any other type of structure apart from a sphere. When the diameter of a sphere doubles, the surface area increases 4 fold and the volume increases 8 fold, which makes it materially very efficient. The entire structure of the model neurocranium resembles a sphere-like geodesic dome (fig. 3a), with a dural ‘skin’ under tension and bones enmeshed as an endoskeleton. In mechanical terms, a tensegrity structure cannot be anything other than in a balanced state of minimal energy throughout.35,45

3.4. Integration
In a tensegrity structure, a change in any one tension or compression element causes the whole shape to alter and distort, through reciprocal tension, distributing the stresses to all other points of attachment.29,30,32,35-41 In this model, the occiput is fixed at the condyles whilst the sphenoid exerts an elastic compression through the spheno-basilar synchondrosis. Apart from this, the frontal, ethmoid, sphenoid, occiput, temporals and parietals do not make direct contact with each other at any point (‘discontinuous compression’), and are suspended all around (‘continuous tension’) (fig. 8). It has been known for a long time that cranial base dysmorphology may be fundamental to the aetiology of premature suture closure.1,2

The cartilage growth plates in the chondrocranium have been shown to respond to mechanical stresses, although normally the spheno-basilar region is the only one to remain metabolically active for very long after birth, and remains so until adolescence.6,49,50 The dural sheets connecting across the neurocranium short cut mechanical stresses from one part to the other1 - the falx cerebri/cerebelli linking the ethmoid, frontal, parietals and occiput; and the tentorium cerebelli linking the sphenoid, temporals and occiput with the falx along the straight sinus. [The wire model shown is an extra figure, and the shapes correspond to the edges of the inner bone surfaces. All the 'bones' in this model remain separated because of the tensegrity configuration.]
The icosahedron has several attributes that are advantageous for modelling biological structures.35,36

 A full account is beyond the scope of this paper, but a few significant points are worth mentioning. It is fully triangulated, which is the most stable of truss configurations (figure 3a); it comes closest to being spherical, with the largest volume to surface area ratio of all the regular polyhedrons - making it materially efficient; its surfaces can be divided equally into smaller triangles and the structure scaled up into higher frequencies - making it even more energetically efficient;43-45 it provides a link between close-packing in 2 and 3 dimensions; and as a fractal generator, it can polymerize into a sheet, stack in a column or helix, and create complex patterns and shapes. Fractal analysis is commonly applied to natural structures. Their formal definition is rather obtuse for the purposes of this paper, but a working definition could be: ‘A shape or pattern which evolves as it changes, reappearing in a hierarchy of different size scales’. Although the frequencies and amplitudes of the ‘wave’ curvatures seen at the bone edges in figures 9a and 9b vary, they are both examples of a fractal nature – with a similar pattern appearing at different size scales.51 Fractals are probably relevant to linking structural hierarchies throughout the body,2,32,35,36 thus making the icosahedron particularly versatile, because it also gives rise to structures with geodesic dome and tensegrity properties.

As the vault bones approximate each other, a sort of hybrid geodesic dome/tensegrity structure would provide the required rigidity for brain protection, but with the facility for micro-mobility at the sutures.1,2,15 Tensegrity in the cranium allows for flexibility during development, and whatever other functions that patent sutures might serve beyond cranial expansion.4,7,15,21 [It is likely that this explains some of the underlying mechanisms described by 'cranial' osteopaths.] The cranial base naturally develops a geodesic structure and provides a platform from which the vault bones could expand, through tensegrity, to accommodate brain growth. If the transfer of tensional forces in the dura mater, and the suggested mechanisms illustrated in figure 9 really do form an essential part of sutural patency, an aberration in this system which leads to compressive bone contact at any point could be one step towards a rigid geodesic dome cranium.1,5,15 This may explain why cartilage sometimes appears in sutural joints.1,14
A local tensional stress generated within the cellular cytoskeleton could transfer to the extracellular matrix of the dura mater and produce effects on other cells at some distance, with structural rearrangements throughout the network. Long-distance transfer of mechanical forces between different tissues could contribute to dural development, and be responsible for spatially orchestrating bone growth and expansion.3,28,29,30,32,34,47,49,52 Similarly, an ‘aberrant’ tensile stress from elsewhere in the cranium could exert its effects on sutures some distance away, and contribute to a change in interactions between the dura mater, bones and brain, ultimately leading to premature synostosis.1,2

The tensegrity model is a novel approach to understanding how the cranial vault could retain its stability without relying on an expansive force from an underlying brain, a situation currently unresolved.1-6

Tensional forces in the dura mater [and suture] have the effect of pushing the bones apart, whilst at the same time integrating them into a single functional unit. Sutural patency depends on the separation of cranial bones throughout normal development, and the model describes how tension in the dura mater achieves this, and influences sutural phenotype. Cells of the dura mater respond to brain expansion and influence bone growth, allowing the cranium to match the spatial requirements of the developing brain, whilst remaining one step ahead and retaining a certain amount of autonomy. Tensegrity may also be an integrating mechanism in a hierarchical structure that extends from the cell to the whole organism, with complex 3D patterns the outcome of a network of interactions which feedback on each other.2,29,30,32,36-40,47,52 This provides a context for this model and could indicate a new approach to understanding the pathologies seen in the neonate.

One of the most significant aspects of biology is the efficiency with which it packs multiple functions into minimal space. This presents a conundrum in physical modelling, as any structure will inevitably be limited in its behaviour if it is incomplete or in isolation. It must be emphasized that much of the supporting evidence for this model is circumstantial, and more research is needed to verify it, but it is compatible with current understandings of cranial physiology, and has a contribution to make to a hierarchical systems approach to whole body biomechanics.

I wish to express my sincere appreciation to Nic Woodhead, Chris Stapleton and Andrea Rippe, for their contributions and thoughts during discussions in the preparation of this paper.

Sunday, July 15, 2012

Tensegrity in Biology

This is the work of Graham Scarr D.O.  It is such a great piece of work that I had to include it this blog.  Although I try to stick to "original" work, this one is absolutely fabulous.  Very long, but worth every minute.  Enjoy! 


BIO-TENSEGRITY is a structural system that maintains stability by distributing mechanical forces through components that interact in just one of two different ways - attraction (tension) or repulsion (compression). Such simplicity is due to some basic laws of physics and because it is energetically efficient is likely to have developed throughout evolution to produce biological organisms of great complexity. Tensegrity systems eliminate the need for bulky elements and are lightweight structures with a high resiliency that depends on the integration of every part. It seems to be pervasive in biology and is described in the human body through molecules, cells, the extra-cellular matrix, vascular system and entire musculo-skeletal-fascial system.

Many examples of tensegrity in biology can be found but they often occur in obscure journals or are written in complicated scientific language; they are described here in the hope of making them more accessible. Most experimental work has been carried out on cells, which are essentially complete organisms, while generalizations from a 'whole-body' perspective have been reasoned from first principles or inferred from models and observation. Because tensegrity describes biological systems more thoroughly it is only a matter of time before it becomes the standard approach to bio-mechanics.


Structural hierarchies; Cellular cytoskeleton and morphogenesis; Cell cortex; Helix; Collagen; Fascial system; Cranal vault; Spider silk; Shoulder joint, elbow and pelvis; Respiratory system of the bird; Mammalian lung; Central nervous system; DNA nanostructures.

Biological structures appear to be very different to the simple tensegrity models that we make with sticks and bits of string, but they conform to the same simple rules of geodesic geometry, close-packing and symmetry, to build more complex structures (the basic principles and construction of a tensegrity structure are given on the geodesics and models pages). Physical models are usually built with components on the same size scale but the essence of bio-tensegrity is structural and functional interdependency between components at multiple size scales. One particular aspect that is often not appreciated in simple models is structural hierarchies and an example of one is shown here.


Hierarchies are ubiquitous in biology and an inherent capability of tensegrity configurations. They provide a mechanism for efficient packing of components, the dissipation of potentially damaging stresses, and a functional connection at every level, from the simplest to the most complex, with the entire system acting as a unit. Each component in a hierarchy is made from smaller components, with each of these made from smaller still, often repeating in a fractal-like manner.

Tensegrity hierarchies achieve a significant reduction in mass and as tension always tries to reduce itself they automatically balance in the most energy-efficient configuration. Because every part influences every other part forces are distributed throughout the network and stress concentrations avoided.

The separation of tension and compression into separate components means that material properties can be optimized and these forces transferred down to a smaller scale with the elimination of damaging shear-stresses and bending moments. At atomic and molecular levels they automatically balance in the most energetically efficient configuration to form crystals and molecules which are, therefore, tensegrity structures in their own right. The forces of tension and compression always act in straight lines, but components arranged in hierarchies can give the appearance of curves at larger scales, and curves are common in biology (see definitions page).

The helix is a common motif in protein structure and a general model for coiled winding at multiple size scales throughout the body; its functional value has been demonstrated in a diverse group of organisms and is also described in relation to tensegrity (also see geodesics and helix pages).

The hierarchical arrangement of helixes in muscle shows this scaling up and links with the close-packing geometry of a myofibril.

At the nano level, tensegrity helixes describe the mechanical behaviour of the cellular cytoskeleton - a semi-autonomous structural system amenable to such analysis because of its size.


Ingber showed how the cytoskeleton behaves as a multi-functional tensegrity structure that influences cell shape and activates multiple intra-cellular signalling cascades. Within the cell, microtubules under compression are balanced by microfilaments of actin under tension with bundles of actin and spectrin fibres playing similar respective roles in the cell cortex. Intermediate filaments link them all together from the nucleus to the cell membrane so that any change in force at one part of the structure causes the entire cytoskeleton to alter cell shape. Tension is generated through the action of actomyosin motors and polymerization of microtubules.

Many enzymes and substrates are immobilized on the cytoskeletal lattice and mediate critical metabolic functions including glycolysis, protein synthesis and messenger RNA transcription. DNA replication and transcription are also carried out on nuclear scaffolds that are continuous with the rest of the cytoskeleton. Changes in the cytoskeleton and cell shape thus alter cellular biochemistry leading to a switch between different functional states such as growth, differentiation or apoptosis.

Experiments that allowed individual cells to assume certain shapes showed that those able to distort or spread had the highest rates of growth; rounded cells became apoptotic (died) while those intermediate in shape became quiescent and differentiated. Cells also tend to extend new motile processes (lamellipodia and filopodia) on sharp corners rather than blunt ones and this is linked with the cytoskeleton.

The cytoskeleton connects to the extracellular matrix (ECM) and other cells through adhesion molecules such as integrins and cadherins, respectively. These transmembrane proteins create a mechanical coupling that transfers tension generated within the cytoskeleton to the ECM and adjacent cells. Because a prestressed state of tension exists between them, so a change in ECM tension also causes a realignment of structures within the cytoplasm and a change in cell function; this process is known as mechanotransduction.

Integrins act as strain gauges that respond to changes in tension on both sides of the membrane and their ativation promotes the binding of proteins such as talin, vinculin, alpha-actinin, paxillin and zyxin. These physically link them to contractile actin bundles ('stress fibres') in the cytoskeleton and form part of a specialized complex called a 'focal adhesion'.

The transfer of tension from the ECM stimulates actomyosin tension generation, causing an increase in integrin binding and clustering, and the recruitment of more focal adhesion proteins that balance the ECM tension. Force transfer is also transmitted via the cytoskeleton to other focal adhesions and integrins, stress-sensitive ion channels, cadherins, caveolae, primary cilia and nuclear structures etc.

The attachment of fibronectin molecules (ECM) to the outside of certain integrins (alpha-5-beta-1) is what stimulates a reorganization of actin in the cytoskeleton and the accumulation of focal adhesions to the area. Changes in tension then feed back to cause unfolding of the fibronectin molecule and exposure of cryptic sites within it that lead to fibrillogenesis of itself and ultimately of collagen. The spacing of fibronectin nanofibrils on the outside of the membrane is proportional to the spacing of cross-linked actin bundles in the cytoskeleton and the cell is thus able to maintain tight regulatory control over collagen morphogenesis.

During embryogenesis, tension generated in the cytoskeleton is transferable to the ECM, and changes in matrix tension cause a realignment of structures within the cytoplasm and a change in cell function. Consequently changes in enzymatic activity produce local and regional variations in the compliance of the basal membrane and cells adhering to these regions then distort more than neighbouring cells. Mitogen stimulation can then lead to the development of more complex tissue patterns such as budding, branching (alveoli) and tubular structures (capillaries) or produce motile cells that are able to migrate(epithelial-mesenchymal transition).

Branching can create a pattern similar to the 'Koch snowflake' fractal and it has been suggested that the position of coronary artery lesions around the heart follows a pattern related to the Fibonacci sequence and Golden Mean, maximising perfusion of the myocardial bed.Gibson Simple geometry seems to get everywhere.

If the reciprocal transfer of mechanical forces between the cytoskeleton and extracellular matrix orchestrates cellular growth and expansion, it is likely that complex multi-cellular tissue patterns can emerge based on the same principles, and continuity of the extracellular matrix with the fascia could extend this throughout the entire body. Levin and Ingber have both proposed this as a tensegrity configuration but it is not universally accepted as yet; however, new developments in computer modelling confirm the relevance of tensegrity to the cytoskeleton  and multi-cellular systems.


The cellular cortex (cortical cytoskeleton) lying just beneath the cell membrane can be considered as many tensegrity units within a geodesic dome and has been modelled around an icosahedron. It is essentially made from triangulated hexagons of the helical protein spectrin (tension) coupled to underlying bundles of the helical protein actin (which in this case are under compression). The network is organized into ~33,000 repeating units, each with a short central actin protofilament, linked by 6 spectrin filaments to a lipid-bound suspension complex (model). About 85% of these units appear as hexagons, with ~3% pentagons and ~8% heptagons, which suggests that the hexagonal arrangement is a biological preference (see the geodesic page).

The erythrocyte with a diameter of 8um has a composite membrane that distorts as it flows through smaller capillaries but allows the cell to recover its biconcave shape. Deformation of the membrane network may cause turbining of the actin protofilaments through the suspension mechanism thereby facilitating oxygen transfer from one side of the membrane to the other. The membrane is itself a bilayered structure of phospholipid molecules with outer heads under tension separated by hydrophobic tails under compression (see 'spheres' on the geodesics page).


The helix is a common motif in protein construction and creates a general model for coiled winding in many other structures throughout the body; it has links to tensegrity through a common origin in the geodesic geometry of the platonic solids (see geodesic and helix pages). Helical molecules behave as tensegrity structures in their own right as they naturally stabilize through a balance between the forces of attraction (tension) and repulsion (compression). Globular proteins contain multiple helical domains and can themselves polymerize into larger helixes such as those in the cytoskeleton. Similar helixes can form hierarchies as they wind around each other to form coiled-coils (eg. spectrin) or assemble into mechanically rigid rods or filaments, or further combine into more complex structures with specialized functions (eg. collagens). Collagens are major structural proteins that consist of several hierachical levels of helixes within bone, tendon, ligaments and fascia.

Axial stretching or compression of a helix initiates rotation in a direction that depends on the direction of twist or chirality. Linking it to another one surrounding it with opposite chirality causes resistance as each helical layer counteracts the rotation of the other. Crossed-fibres of collagen scale up to form tubular helixes in the walls of blood vessels, the urinary system and intestinal tract and influence their mechanical properties. Elastic arteries such as the aorta have walls organized into lamellar units with collagen reinforcement and smooth muscle cells that form crossed-helixes with an orientation of 55o. It is likely that wall components under tension contain sub-structures under compression at a different hierarchical level, and vice versa.

Capillary formation results from tension-dependent interactions between endothelial cells and an extra-cellular scaffold of their own construction and these cells form a selective barrier that allows vascular contents to pass out between capillary walls. The internal cellular cytoskeleton determines cell shape and orientation through tensegrity, is affected by signalling mechanisms and variations in fluid flow, and alters the tension between cells through adherens junctions, ultimately affecting tube permeability. This compares with the wall of a helical tensegrity model that has many gaps but if the struts could be expanded into plates that just touched each other they could be made to 'seal' the internal space; just like the capillary cells.

An optimum helical angle of ~55o balances longitudinal and circumferential stresses and helical fibre arrays allow pressurized tubes to bend smoothly without kinking and resist torsional deformation. Cardiac muscle fibre orientation varies linearly between inner and outer walls, from 55o in one direction to 55o in the other, with tangential spiralling in a transverse plane. The heart is a helical coil of muscle that contracts with left and right-handed twisting motions, and a simple tensegrity pump that may have relevance to cardiac dynamics has also been described using the 'jitterbug' mechanism.

Similar helixes form hierarchical 'tubes within tubes' in fascia and permeate and surround the muscles, limbs and body walls of a huge variety of species, all considered through tensegrity (see helix page). Tubular organs that maintain constant volume throughout changes in shape have been described in the tongues of mammals and lizards, the arms and tentacles of cephalopods and the trunks of elephants. The arrangement of scales in the pangolin and snake illustrate the helix at the macro level although notice how the orientations of left and right-handed helixes on the body are different in the limbs; the pattern in the limbs may be related to the Fibonacci sequence (see geodesics page). The thoraco-lumbar and abdominal fasciae also have a spiral appearance, if only in part, and helical fascial sheaths that transfer tensional forces within and between themselves have been described in controlling movement in a way that the nervous system is incapable of. Fascial tissues are also reinforced by two helical crossed-ply sets of collagen with the 'ideal' resting fibre orientation of 55o (axial) that varies with changing muscle length.


Bones, tendons, ligaments and fascia are all arranged in hierarchies with collagen the most widespread of all structural proteins appearing at several different levels. In collagen type I repeating sequences of amino acids spontaneously form a left-handed helix of procollagen with three of these combining to form a right-handed tropocollagen molecule. Five tropocollagen molecules then coil in a staggered helical array, that lengthens longitudinally by the addition of more tropocollagen to form a microfibril, and pack radially to form a fibril; with higher arrangements forming fibres and then fascicles. (see helix page).

The collagen molecule exists in many different configurations and is a major component of the extracellular matrix (ECM) that surrounds virtually every cell. The matrix attaches to the cellular cytoskeleton through adhesion molecules in the cell membrane and forms a structural framework that extends through the fascia to every level in the body.


Traditionally considered as mere packing tissue fascia has been show to exert considerable influence over muscle generated force transmission. It naturally develops into compartments, or 'tubes within tubes', particularly noticeable in cross-sections of the limbs. Within muscle a delicate network of endomysium surrounds individual muscle fibres and is continuous with the perimysium ensheathing groups of fibres in parallel bundles, or fasciculi. Perimysial septa are themselves inward extensions of the epimysium, which covers the muscle and is continuous with the fascia investing whole muscle groups. These fascial tissues are reinforced by two helical crossed-ply sets of collagen with the 'ideal' resting fibre orientation of 55o (axial) that varies with changing muscle length (see helix page).

The fascial system has been described as a tensegrity system which might seem rather strange initially because there dont appear to be any compression struts. The extracellular matrix/fascial system is a complex biological hierarchy which means that it is likely to be different to simple models. As tension and compression always occur together it must have structures under tension and others under compression.

Considering a sheet of tensioned fascia between two bones, or even both ends of the same bone, any two points along that tension line (x,y) will be separated by a pull from either end. The points are held apart by tension but as one of the functions of a 'strut' is to hold two points apart (nodes) the tissue between them is behaving as such to other parts lower down in a tensegrity hierarchy. Collagen and proteoglycans probably interact in a tensegrity way at the nano level. Fascia could thus be considered as a network of tensioned cables and [virtual] 'struts' but only if it is part of a larger tensegrity system that includes 'real' struts such as bones at a higher level. The basic tensegrity principles remain the same but the description starts to become a bit more complex (see definitions page).

At the macro level,bones (struts) are compressed by muscles and fascia under tension. Muscles are cables that generate axial tension on contraction, but the resulting changes in their diameter also make them variable length compression struts perpendicular to this, which probably contributes to the tension in associated fascia and force appearing at tendons. The balance of ‘agonist/antagonist’ muscle tensions has also been shown to reduce stress concentrations in long bones (bending stresses) making them compatible with the resiliency required of tensegrity struts.

Guimberteau described a 'microvacuolar' system that allows sliding between different tissues throughout the body as the basic network of tissue organization. These microvacuoles are collagen envlopes containing proteoglycans and "histological continuum without any clear separation" was observed between fascia, skin, muscles and vasculature; sounds remarkably like a tensegrity.


Many aspects of normal cranial development are poorly understood, with some previously held views now outdated, but a tensegrity model can explain some of these and improve understanding of normal and abnormal development. A more detailed explanation is given on the cranial vault page.

The skull is generally considered to be a solid box but is actually made up of 22 bones most of which remain distinct throughout life; several of these bones contribute to the cranial vault that covers and protects the brain. The sutural spaces between the bones are filled with fibrous tissue and are important to the mechanism that allows the cranium to grow larger and accommodate the developing brain. A tough membrane called the dura mater lines the internal surface of the bones. Until recently the general opinion was that the growing brain pushes the bones outwards but this is now known not to be the case; an increase in dural mater tension does stimulate bone growth but the mechanism is much more complex than previously thought and better explained through tensegrity.

The geodesic dome (icosahedron) is developed into a tensegrity model (T6-sphere) with the struts connecting opposite vertices. The straight struts are then replaced with curved struts and these are replaced with curved plates (not shown) to produce the model skull with bones that surround a central space. The bones of the cranial vault are tensioned by the dura mater (elastic cord in model) and configured as a tensegrity structure. The curved struts are at the top of a bone hierarchy (at least seven different levels within bone) that extends down to the molecular level (see definitions page).

Adult bones are separated by a sutural gap of about 100 microns and have curved outlines with a fractal relationship between them. Dural membrane (tension cords) attached to the peaks of bone convexities, and the alignment of collagen fibres in sutures, cause adjacent bones to be pushed apart as they form the tensegrity structure. (see definitions page).

The vault bones develop totally within membrane which they separate into an outer periosteum and inner dura mater membrane as they grow around their edges (bone fronts). Tension in the dural membrane beneath the sutures, combined with chemical signals from the osteoblasts (bone-making cells) at the bone fronts, influence the cytoskeleton of epithelial cells in the membrane beneath the suture through the process of mechanotransduction, and change cell activity that results in further bone growth. It is a cyclic mechanism that regulates bone growth and maintains sutural patency up until at least seven years of age (when the brain stops growing). Even after this age the sutures should remain patent and may contribute to the small amounts of bone mobility recognized by 'cranial' osteopaths and 'cranio-sacral' therapists.

The bones form a dome that provides protection to the brain, compression struts of a tensegrity structure that maintains sutural flexibility and accomodates brain growth, and a microstructure that transfers external forces down through a hierarchy to the nano-scale. The centre of the bone is a honeycomb like structure made from collagen and mineral reinforcement. Curved-strut plates are still compatible with tensegrity when considered in terms of hierarchies because the forces of tension and compression ultimately act in straight lines at some smaller scale.

A tensegrity configuration allows the skull to enlarge and remain one step in front of the growing brain rather than being pushed out by it. It also allows the skull to respond to the mechanical demands of external muscular and fascial structures and integrates the entire cranium. The dural membrane also reduplicates into four sheets that penetrate the cranial cavity (falx cerebri and cerebellum and two halves of the tentorium cerebelli). Abnormalities in the cranial base may alter the tension pattern in these sheets and cause the sutural/dural mechanism to behave differently, leading to premature sutural fusion in babies (craniosynostosis) and malformation in head shape (plagiocephaly).


Spider silk can be considered as a tensegrity structure with some similarities to fascia. It is a composite material with a hierarchical structure composed mainly of the proteins Spidroin I and II. Spidroin I consists of poly-alanine chains in anti-parallel beta-sheet conformation packed into an orthorhombic crystallite unit. These crystallites are interconnected by helical oligopeptides rich in glycine that form a polypeptide chain network within an amorphous glycine-rich matrix. The overall network shape is circular segments (40-80 nm diameters) interconnecting in series to form a silk fibril with many of these arranged laterally to form the silk thread with a diameter of 4-5 microns. It is the regular spacing and orientation of these crystallite units and hierarchical structure that suggests that it is a tensegrity structure.

An analogy can be made between a spiders web and the spoked bicycle wheel where cable tension is balanced by compression within the rim and central hub. If the cables were relatively elastic the central hub could be moved around always returning to the same position of stable equilibrium. The multiple hubs in the second model could also be reduced so that they looked like single nodes between crossing cables (although under a microscope they would appear unchanged). The common spider web is made from silk woven into a configuration of radial and spiral tension cables attached to a gate post and tree. These latter form a single compression element connected through the ground like the rim of the bicycle wheel. Each of the connecting nodes between cables represents one of many ‘hubs’ that can be displaced within the elastic tension network but that always returns to the same position of stable equilibrium, one of the conditions of tensegrity. However these examples of the bicycle wheel and spiders web should probably be considered as on the limit of 'tensegrity' (see definitions page).


Levin was the first to describe the higher complexities of the human body in terms of tensegrity using the analogy of a bicycle wheel. Here the outer rim and central hub are considered as compression elements held in place by a network of wire spokes in reciprocal tension. This type of wheel is a self-contained entity maintained in perfect balance throughout with no bending moments or torque, no fulcrum of action, and no levers. He suggested that the scapula functions as the hub of such a wheel, in effect as a sesamoid bone, and transfers its load to the axial skeleton through muscular and fascial attachments. The sterno-clavicular joint is not really in a position to accept much compressional load and the transfer of axial compression across the gleno-humeral joint is at maximum only when loaded at 90o abduction. The joint is essentially a frictionless inclined plane which means that it must rely heavily on ligamentous and muscular tension in all other positions. The humerus as a hub model would function equally well with the arm in any position. Interestingly, different parts of the gleno-humeral capsule that transfer specific tensional stresses can only do so if the capsule is intact, even if those stresses do not apparently pass through the missing parts (this would make sense if the capsule is a tensegrity sheet at a microscopic level).

In a similar way the ulna could be likened to a hub within the distal humeral ‘rim’ of muscle attachments, where load bearing across the joint may be significantly tensional and allow compressional forces to be distributed through a tensioned network and the hand to lift loads much larger than would otherwise be the case (see the elbow page).

The pelvis is also like a wheel, with the iliac crests, anterior spines, pubis and ischia representing the outer rim and the sacrum representing the hub tied in with strong sacro-iliac, sacro-tuberous and sacro-spinous ligaments. Similarly the femoral heads may act like hubs within the ‘spokes’ of the ilio-femoral, pubo-femoral and ischio-femoral ligaments.

'Hinge' joints in the skeleton are very different to those in man-made structures. A standard door hinge has metal plates screwed to the door and fram, with one side of each plate bending around a central metal rod. The rod holds the door part of the hinge to the frame part and is compressed between them as the door swings. Most skeletal joint movements display helicoid motion around a variable fulcrum and in the knee joint it has been shown that there is no continuous compression between bones and cartilage, even when they are pushed together.  A tensegrity ‘hinge’ joint in a biological context doesn’t need a single compression element to carry the entire load and the tensegrity arm models clearly shows these features (see the elbow page for more anatomical details).

The body is made of many joints and they are all linked together through the fascial system. Theo Janssen is a Dutch artist who has linked multiple joint units so that they can walk; a comparison with the human locomotor system seems inevitable. A Janssen mechanism is a structure made of parts with specific lengths according to a precise formula so that they can move as a single entity.

The second model is a multi-joint tensegrity based on the same mechanism with each joint modelled with the six struts of a T6-sphere. Some of the struts are elongated so that they become parts of two of these joints. The rotation then produces the same relative motion and interactions although it needs a bit more head scratching to work out which parts are pushing and pulling during the movement. The long thin struts between the 'joints' are substructures in a hierarchy where the next level above is comparable to the metal plates of the original TJ mechanism. Apart from the fixings to the wooden block there are no fixed fulcrums, levers, or moments of inertia in this model. This model shows how the movement of a tensegrity joint can cause other joints to move passively at a basic level and that muscles just refine that movement further down the chain as a higher active level of control. We can separate passive and active components in models but in biology they are often inseparable. This model still has a long way to go but it is one more step.

According to Wolff’s law, tensional forces remodel the bony contours and alter the positions and orientations of their attachments, contributing to the complexity of shapes apparent in the skeleton. As part of a tensegrity structure each attachment would influence all the others, distributing forces throughout the system and avoiding points of potential weakness, in contrast to a rod or truss which is vulnerable to buckling. Such a mechanism would be an advantage in long-necked animals such as giraffes, camels and dinosaurs, where the load from the head is distributed throughout the neck, as opposed to a stress-ridden cantilever system such as the Forth Bridge.

The erect spine and bipedal weight bearing capability of humans has traditionally been viewed as a tower of bricks and compressed disc joints that transfer the body weight down through each segment until it reaches the sacrum; but a vertical spine is a relatively rarity amongst vertebrates. Most other species have little or no use for a compressive vertebral column which is frequently portrayed as a horizontal truss and cantilever support system. As the main difference in vertebrate anatomies is in the detail it seems reasonable to suppose that they have some structural properties in common. Tensegrities are omni-directional ie. they are stable irrespective of the direction of loading, and the spine, pelvis and shoulder all demonstrate this property (within physiological limits), enabling dancers to tip-toe on one leg and acrobats to balance on one hand.


The respiratory system of the bird differs substantially from the mammalian lung; it is an exceptionally efficient gas exchanger that processes the large amounts of oxygen required to sustain flight. Some of the reasons for this are considered to be its geodesic design and hierarchical tensegrity arrangement that mechanically couples each part into a functionally unified structure. The volume of the bird lung is about 27% less than that of a mammal of similar body mass although the respiratory surface area is about 15% greater. The lung is attached to a rigid ribcage and its volume changes relatively little during a respiratory cycle (1.4%); instead, separate air sacs act like bellows and cause unidirectional and continuous ventilation. The air passages of the lung have a hierarchical arrangement with two-thirds of the lung volume taken up with several hundred parabronchi; their polygonal atrial openings each give rise to several funnel shape ducts (infundibulae) that terminate in numerous air capillaries, the terminal respiratory units (fig. ?). Both blood and air capillaries anastomose and interdigitate to form a tightly packaged three-dimensional network.

The parabronchi develop from epithelial cells that are compressed due to space restraint and naturally form hexagons with lumens that enlarge during development (fig. ?). This geodesic packing arrangement persists into the adult and makes the most economical utilization of space, thus maximizing the potential respiratory surface area. The constitutive parts of the parabronchus act together to function as an integrated unit that prevents the air capillaries from collapsing under compression and blood capillaries from distending with over-perfusion; mechanically, it is rather similar to the tensegrity bicycle wheel described in chapter 2.

Intertwined smooth muscle bundles and collagenous tissue surround the atrial openings into the central lumen and form a complex helical arrangement. The collagen forms an intricate system of longitudinal, transverse and oblique fibres that connect to elastic fibres in the interatrial septa and floor of each atrium, and continue as the interfundibula septa that eventually becomes the basement membrane surrounding the exchange tissues. The smooth muscle, collagen and elastic fibres surrounding the atrial openings form an internal parabronchial column that lies next to the lumen (fig. ?). The collagenous septa and exchange tissues are also continuous with the interparabronchial septa that enclose the walls of larger blood vessels and form an external parabronchial column. The exchange tissues and associated septa are thus suspended between the internal and external parabronchial columns like the spokes in a bicycle wheel.

Contraction of smooth muscles around the atrium tenses the interatrial and interfundibula septae and stretches the elastic fibres, with collagen limiting their stretchability; the elastic fibres then act as energy-storage elements and recoil when the muscles relax. The interatrial, interfundibula and interparabronchial septa thus balance the centripetal force produced by contraction of the smooth muscle. An outward centrifugal force is also produced, by surface tension generated within the air capillaries and the prevailing intramural pressure in the interparabronchial arteries, and this is balanced by the elastic and inflexible collagen fibres. The parabronchus thus exists in a dynamically tensed state, with the inward pull of the atrial smooth muscles (internal column/wheel hub) ultimately counterbalanced by the interparabronchial septa (external column/wheel rim) and surrounding parabronchi. The morphology of the parabronchus and its constitutive parts thus fits every definition of a tensegrity structure.


The matrix surrounding alveoli is considered to be a tensegrity structure. “The septa between alveoli are very thin and contain a single dense capillary network. They are supported by a fine network of fibres that are interwoven with the capillaries and anchored at both ends in axial fibres that form the network of alveolar entrance rings in the wall of alveolar ducts; and peripheral fibres that extend through interlobular septa towards the pleura. This allows the spreading of the capillaries by mechanical tension on the fibres. Because of this disposition of capillaries and fibres, alveoli in the mature lung are not structural units that can be separated: each of their walls is shared by two adjoining alveoli, both in terms of gas exchange with the capillary and with respect to mechanical support. Even the epithelial lining is shared by two adjacent alveoli as it extends through the pores of Kohn... This disposition of the fibre system makes the lung a tensegrity structure, which means that, in terms of mechanics, the integrity of lung parenchymal structure is exclusively ensured by the tension of the fibre continuum that supports alveolar walls and their capillaries. If one fibre is cut, this causes collapse of the septum followed by rearrangement of the adjacent parts, as occurs in emphysema.


It may be that a tensegrity mechanism is responsible for morphogenesis of the central nervous system, based on some particular characteristics of developing neurites and anatomy of the cerebral cortex. Tension along axons in the white matter is considered to be the primary driving force for cortical folding and is counterbalanced by hydrostatic and growth-generated pressures.

When neurites are transiently stretched, their length increases in proportion to the applied tension, indicating simple elastic behaviour. Under sustained stretching, however, they display visco-elastic properties as the initially elevated tension passively relaxes to a lower level over a period of minutes. Active elongation occurs when tension is maintained above a threshold level and active retraction occurs when tension is fully released. Collectively these passive and active mechanical properties allow neurites to adjust their length by a negative feedback mechanism that tends to maintain a steady tension, much as a fishing line is reeled in or out to regulate tension on the line.

Early in development, neurons migrate to the cortical plate along radial glial cells, differentiate and emanate axons that reach specific target structures. Many structures have pronounced anisotropies in the orientation of axons, dendrites and glial processes; and are under tension. Consequently tissue elasticity will vary in different directions and expansion will occur preferentially in the direction with the greatest compliance, generally perpendicular to the main fibre axis.

The trajectories of long-distance processes arising or terminating in a given region of the cerebral cortex are biased towards one side as they enter and leave exclusively through the underlying white matter. During cerebral growth collective axon tension pulls strongly interconnected regions towards one another (conjoining arrows), forming outward folds (gyri) and allowing weakly connected regions to drift apart and form inward folds (sulci). Consequently cortical cell layers vary in thickness beneath gyri and sulci (similar to the effect of folding a paperback book).


The self-assembly of three-dimensional tensegrity nanostructures of the simplest 3-strut tensegrity model and platonic solids is now possible using single and double strands of synthetic DNA. They confirm that the tensegrity concept can realistically be applied to the evolutionary development of biological structures.