The Architecture: How Muscles Work in the Context of the Skeletal Framework

 

There is in all human movement a basic organizing principle, an active force that ensures effortlessness, vitality, and optimal control in everything we do. It is the foundation for healthful functioning throughout life; it is also the basic mechanism over which we must gain control as the basis for higher levels of awareness and skill. This principle has not been taught as part of any spiritual disciplines, yet it is fundamental to self-knowledge and will one day be understood as a key element in self-realization. It is not accepted or understood by modern science, yet is demonstrable and observable and will one day be considered among the most important principles in our understanding of the natural world. It is not taught in conjunction with any holistic or medical techniques, yet it is as central and fundamental to health as any principle taught in Western or Eastern medicine. It is not taught in movement training programs, and yet it is the key system governing how the body is organized to move.

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I am speaking about the central organizing principle in movement, described in these pages as the postural neuromuscular reflex, or PNR system. Today there are virtually hundreds of movement and exercise methods designed to increase strength and flexibility, all of them promising improved health and functioning. As we’ll see in these talks, however, the basis for human as well as animal movement is a natural system that ensures effortless action without any meddling or interference from us. When this system works well, muscles do not strain but are naturally healthy and toned; joints have room and are supported so that they can work with maximum ease; breathing is full and unimpeded; vitality is heightened by improved muscle tone; and circulation is maximized by a lack of excessive contraction in muscles. In short, the key to improved movement and health is not the practice of this method or that, but an understanding of how the body is designed to function naturally--that is, with a minimum of strain and effortless grace based on our body’s natural design.

 

The Body’s Elastic Latticework

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When we ask ourselves what the function of muscles is, what comes most quickly to mind is that muscles contract to produce movement. To lift a glass, walk down the street or type a letter, we have to contract, or tighten, particular muscles; otherwise we would not be able to produce movement in space, manipulate objects, speak, or even breathe.

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But movement is not nearly as simple as that, because in order to move in space or even to move an arm, we first have to maintain our skeletal structure upright in the field of gravity—in other words, we have to maintain postural support. Most of us have heard about the postural muscles that keep us upright—most notably in the neck, back, and legs. By contracting, it is said, these muscles keep the head from toppling forward, the trunk from buckling, and the legs from collapsing under us.

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But exactly how do these muscles work? When you lift a phone book, muscles in your shoulder and arm contract, moving the levers of the arm. Using a great deal of force to accomplish the task is a perfectly acceptable strategy because you don’t have to hold the book up for very long. If your arm tires, no matter; you can soon put the book down and rest your muscles. However, this strategy is quite inadequate for supporting our entire body in the gravitational field. To sit or stand, we must maintain the entire trunk erect for hours at a time; trying to do this by simply contracting muscles would be impossibly inefficient, and nature cannot afford to be inefficient.

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How then do we maintain our upright posture, if not by forcibly contracting muscles? One obvious clue is the dynamic way our body parts are organized. Look, for instance, at the muscles on the nape of the neck. One of the primary functions of these muscles, which connect the back of the skull to the spine and ribs, is to keep the head from falling forward. Why then do these muscles, which will tend to contract if unopposed, not tighten and pull the head back? The answer is that the head is weighted forward, which keeps these muscles lengthened. The neck muscles are performing work, but instead of forcibly pulling the skull back, they are stretched between the skull and the spine so that, even while the muscles maintain stability in the skeleton, the skeleton maintains length in the muscles.

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The Concept of Tensegrity

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How is it possible for our muscles to maintain upright support by elastically stretching or lengthening rather than by contracting? Upright support is achieved through the activity of tensile elastic members rather than through contraction. One simple example of this is a tent with a central pole and guy wires that hold it up. The guy wires keep the pole from falling over, but at the same time the pole exerts stretch on the guy wires. A more complex example is a tensegrity structure, an architectural design featuring guy wires coupled with solid members to create structural support without any traditional pillars or walls. When a tensegrity structure is working properly, the wires are stretched between the solid members, so that support is distributed as widely as possible between all the parts.

 

In humans, and in all land animals that must contend with gravity, we find a vastly more sophisticated variation on this approach: a varied and complex system of struts—the skeleton—maintains stretch on muscles while the muscles maintain tension or tone to support the bones. This marvelously complex architectural design for upright support distributes the work of the muscles over many meters of support so that the burden does not fall on just a few muscles, creating an amazingly strong and versatile structure for upright support.

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The muscular system, then,  is not simply an assortment of contracting muscles, but a complex system of elastic tissues that are kept on stretch by bones, which act as counterbalances, spacers, and struts. This enables muscles to do work in as efficient a manner as possible. It also enables us to maintain support in the gravitational field with a minimum of effort and strain.

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This principle of effortlessness or economy of action is found throughout the animal kingdom. We are all familiar with the beautiful, effortless grace of cats, which we admire for their ease of motion. But there is hardly an animal on the planet, except perhaps for modern man, that does not exhibit its own form of grace. Wolves, beavers, birds, snakes—all seem to move with an effortless grace perfectly adapted to their environment and lifestyle; even elephants, despite their enormous size, are remarkably light-footed and efficient in their movements. In each of these creatures, muscles act in concert with the skeleton to produce a kind of elastic/strut system that utilizes minimal muscle contraction and maximizes economy of effort.

 

Tensegrity v. Compression Structures

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Tensegrity structures are usually compared to more traditional architectural designs such as columns, arches and walls, which are designed to resist compression and to bear weight. Whether made of bricks, girders, blocks of stone, dried dirt, or concrete, they have been used for centuries in the construction of cathedrals, coliseums, temples, aqueducts, and houses of all kinds. Even an arch is a compression structure that distributes downward pressure laterally to its base on either side.

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A tensegrity structure, in contrast, combines compression members and tensile members to produce a strong, lightweight structure. The word “tensegrity” is a combination of “tensional” and “integrity”--a term coined by Buckminster Fuller, who also invented and utilized the concept. In this design, the rigid members don’t bear weight but provide opposition to the tension members, which in turn pull on the compression members.

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A familiar example of this concept in action is a balloon. Gas molecules are trapped inside the balloon, expanding and pressing it outward. The envelope of the balloon, which resists being pulled apart, doesn’t press outward like a column that supports weight, but actually pulls inward, opposing the outwardly expanding gas. This opposition between the tensile strength of the rubber skin of the balloon and the expanding gas creates a supportive structure. Tensegrity structures used in building, such as geodesic domes and tents, are not quite the same as a balloon. But as with a balloon, the compression members oppose the tensile members to produce total support. In essence, the solid members space apart the tension or guy wires, and the guy wires pull on the solid members to create a structurally powerful system.

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A tensegrity structure, then, can be defined as a continuous tensile network, interspersed with struts that create framing against which the tensile elements pull. In compression structures, the bricks or columns bear all the weight; in tensegrity structures much of the work is borne by the tensile members, which distribute the strain evenly throughout. This makes for a very efficient design that is stronger and more lightweight than walls or beams, and uses less material.

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A fascinating study of tensegrity in action was recently reported in The New York Times. It compared European men carrying heavy loads on their backs to Kenyan women carrying weight on their heads. The women, it turns out, carried 20% of their body weight with no additional expenditure of calories as compared to the men, who used far more effort. The study concluded that this was because the women altered their gait but did not alter their upright support mechanism when carrying a load on their heads, whereas the European men did and therefore had to use far more muscular effort to support their packs. In essence, each woman was able to carry the weight on top of her head and vertical spine without disturbing the tensegrity design of the musculoskeletal system, so that the load was distributed over the entire tensegrity structure rather than straining particular muscles.

 

Struts, Spacers, and Counterbalances

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Let’s look in more detail at the actual arrangement of bones that enables muscles to work in an elastic way. In traditional kinesiology and physiology, muscles are seen as motors that act upon bones to produce movement—a mechanical, one-way description that doesn’t explain how muscles cooperate with bones to produce effortless upright support.

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But as we’ve seen, muscles act within the context of a structure that lengthens them, and what keeps them lengthening is the design of the skeleton itself.  Look, for example, at the spine and skull of a cat. The cat is a four-footed animal with a long spine and tail that are positioned horizontally in space, with the skull in front. Since the cat’s skull is cantilevered out in front of the spine, it has no support from below and is therefore always tending to fall, which means that the muscles and ligaments at the nape of the cat’s neck must keep it from falling. And that is exactly what these muscles do: they maintain the support the skull. At the same time, however, the weight of the skull prevents these muscles from shortening. You’ll never see a cat with shortened or habitually contracted neck muscles because the skull, cantilevered at the end of the spine, exerts a continuous stretch on the muscles of the neck. When the cat performs movements, it can contract these muscles as powerfully as it wants and they will never become shortened, because they operate in the context of a lengthened or elastic condition that is maintained by the cat’s architectural design.

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In humans, muscles are stretched across skeletal parts as they are in other animals, but the situation is complicated considerably by our upright posture. Since we are vertically poised on two feet, our spines have to lengthen and point upward. Gravity, meanwhile, is pulling all of our body parts downward toward the center of the earth. To counteract this pull in an efficient way, nature has got to be fairly clever. If, for instance, you simply tried to pull yourself up by tightening your muscles, then the guy wires would have to pull very hard in a downward direction, creating forces you don’t want and using far more tension than would be practicable--not to mention that this would fix the entire structure and prevent movement, which of course would defeat the entire purpose of the structure, which is to produce movement. Again, nature is far more efficient than that.

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To solve this problem, nature came up with an ingenious architectural design. Unlike the spine of a cat, the human spine is not horizontal but vertical, with the skull sitting on top of the spine. How then can the skull exert stretch on the neck muscles? The answer is that the skull is not evenly balanced on the spine but off-balance so that it tends to fall or tip forward, acting as a counterbalance and exerting stretch on the muscles of the neck, just as in the cat, but from a different direction and without as much force. In both human and cat, the skeleton is designed in such a way that one part (the skull) moves in relation to another part  (the spine) and exerts stretch on muscles.

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The human spine is also very cleverly designed. First of all, the vertebrae act as spacers, keeping the small muscles of the spine stretched between the processes, or protrusions, of the vertebrae, to which they attach. Second, the spine has several curves that can buckle, as when we slump. But if the head acts as a counterbalance at the top end of the spine, and the tail drops at the bottom end, the curves of the spine are reduced so that, instead of buckling, it actually lengthens in response to gravity.

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This tendency to lengthen includes several other key structures. When the spine lengthens as a whole, then the muscles along the front of the torso, which are hung from above, release to allow the trunk to lengthen in front; this is true of the throat musculature as well, which is elastically slung between the skull and clavicle. The same is true of the ribs: when the spine lengthens, the oblique muscles of the back and ribs also lengthen and the scapulae and shoulders spread apart, so that the back and shoulders maintain width as well as length. Finally, the legs act as struts so that, instead of tightening, the long muscles of the legs are elastically maintained by the scaffolding of the skeleton.

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In short, muscles are elastically stretched between bony structures. The vertebrae act as spacers so that the small muscles of the back are elastically stretched, and the spine as a whole is a spacer for the longer back muscles which are also elastically stretched. The head goes up on top of the spine, and the pelvis tends to drop away from the head, acting as a counterbalance at the bottom end of the spine to help maintain spinal length. The leg bones are vertically stacked, acting as struts for the leg muscles. The muscles on the front of the body hang down from the skull and let go to allow the front to be fully lengthened; the throat is also suspended from the skull. Finally, the ribs (which do not hang down as in four-footed animals but slant downwards) act as struts to which the oblique muscles of the back and ribs attach. These oblique muscles release to allow the ribs to move freely and the shoulder girdle to spread apart, so that the entire back is widened and elastic.

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The human tensegrity design not only has different elements but also different layers. At the deepest layer, the vertebrae function as spacers for the small postural muscles that support the curves of the spine and maintain its length. The spine, in turn, lengthens the long, powerful spinal muscles attaching to the vertebrae and the ribs. When the trunk as a whole is supported in this way, the muscles of the shoulder girdle let go of the scapula and upper arms so that the shoulder girdle widens. The middle and outer layers of back muscles also let go so that the back widens and fills out, and the oblique muscles of the back let go of the ribs which, acting as struts, can then move freely.

 

To summarize:

1. The head balances forward to counteract the pull of neck extensors

2. The head goes up, the spine lengthens, and the tail drops to lengthen the back muscles

3. The front of the body lengthens and the throat hangs freely

4. The shoulder girdle widens and the back muscles spread to allow the ribs to move freely

5. The leg muscles lengthen to allow the leg-bone struts to support the body

 

Elasticity and the Tensegrity Design

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In order for the tensegrity design to work properly, muscles must lengthen so that the entire structure can be erected and supported and the workload can be distributed over the entire network of muscles. When this happens, we get a sense of upward force without effort, of natural springiness against gravity. As we all know, however, the system does not always work the way it is designed to work, which is where neurodynamics comes in. If, for instance, you pull your head back and slump while sitting in a chair, the whole system begins to collapse. Muscles that need to provide support become slack and, because we still have to support ourselves against gravity, other muscles begin to work far too much. Bones take on added strain and sometimes become distorted, and ligaments that are designed to limit movement and maintain the integrity of joints end up acting like guy wires that are not designed to carry the strain being put on them.

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The key to the proper working of this system is length of muscle. For this to happen, the bones move in opposition so that the muscles perform their work in the context of being stretched. The entire system then works as a tensegrity structure designed to provide support against gravity with a minimum of effort and a maximum of flexibility and mobility. We experience this very clearly when we are in monkey position and the back is lengthening and widening. The back now feels like a continuous sheet because the load is so evenly distributed over the whole. No specific region is strained because no specific area has to absorb the entire load. The tensegrity structure is doing what it is meant to be doing: the muscles are pulling on bones, in the context of the bones opposing muscle and keeping them lengthened, which allows the entire back to function with a minimum of effort.

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For the musculoskeletal system to work properly, then, muscles must lengthen between their bony attachments, which allows the muscles to do their job with a minimum of effort. This principle of lengthening muscle, which was described by F. M. Alexander and which he called “antagonistic action,” cannot be achieved simply by stretching or relaxing muscles, since muscles work in conjunction with bones and must lengthen in this context. It should be made clear that the term, as used here, is not the same as the concept of antagonistic muscles as used in physiology and kinesiology, which refers to the actions of opposing muscles––for instance, the action of the triceps, which extends the arm at the elbow, is antagonistic to that of the biceps, which flexes the arm. In the present context, antagonistic action refers to the condition of a single muscle that is elastically stretched at both poles while performing work and, therefore, functions more efficiently than a shortened muscle.

 

Muscle Length and Connective Tissue

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 There is another reason why muscle length is so important. Many ungulates, or animals with hoofs, have a long nuchal ligament at the nape of their necks. The nuchal ligament is very elastic, so that it rebounds back when stretched. This is very useful to the animal because it must lower its head a long way when it drinks or feeds, and it takes a lot of work to raise it again. The nuchal ligament makes the task a lot easier because, after the animal lowers its head, the rebound energy in the ligament helps to raise it back up with a minimum of effort.

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This same basic principle applies to human muscle tissue. Muscles contract and pull on bones to produce movement. But muscles are also, like the ungulate’s neck ligament, quite elastic. Wrapping around the contractile fibers within the muscle are sheaths of connective tissue; bundled together, they taper into tendons at each end of the muscle and attach to bone. The connective sheaths that form tendons at each end are quite strong and inelastic, but the parts that wrap around the contractile fibers to form the muscle belly are quite elastic and capable of being stretched.

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This connective tissue forms a crucial functional component of muscle because stretching the muscle creates a rebound potential in the muscle, or stored kinetic energy. This rebound potential helps the contractile portion of the muscle to contract when stretched, so that some of the muscle’s ability to resist length and to perform work requires no expenditure of energy. If, on the other hand, the muscle is already shortened and contracted, it has no elastic rebound or stored energy, and the muscle has to work harder to contract or to maintain postural tone.

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Lengthened muscles, then, are far more efficient than shortened ones because they store energy and enable muscle tissue, without any expenditure of energy, to support or move the bones. This is why, as teachers, when we place someone in a position of mechanical advantage, the body becomes more bouncy and supported: the elastic component of the muscle tissue actually produces improved support. In contrast, loss of length in muscles means loss of spring-like support and potential energy; we can see this in the heaviness and stiffness in our legs as we age, in contrast to the spring-like legs of children. Our tensegrity design is based on length in muscles, and length actually creates more support with less energy. 

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Which brings us back to the body’s tensegrity design. When a muscle is lengthening, the energy stored in the muscle actually enables it to support the skeletal framework more efficiently than a shortened muscle. This is what we see when we put someone into monkey and the back lengthens: the elastic tissues seem to produce more efficient support. Lengthening muscles support loads better than shortened ones. For this reason, a muscle cannot be considered healthy simply because it can perform work, because it is built up, toned, or because it has been stretched and relaxed. For a muscle to be healthy, it must function within a skeletal framework that imparts stretch, producing a lively, springy feel in the muscle. This can be brought about only by producing the correct relation of parts and encouraging muscles to let go of bones to produce highly efficient support with a minimum of muscular contraction.

 

The Alexander Technique was developed as a practical means of re-establishing this condition of the muscle system, and it remains to this day the most effective method for restoring this condition. The Dimon Institute offers intensive training in this discipline at our school. However, Alexander's field is much broader than just the re-establishment of coordination, and deeper insights involving behavior and action become accessible with an extensive and practical knowledge of the lengthening design of the human body.

 

 

The Dynamic Relation of Muscle to Bone

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The body is a dynamically supported structure that cannot be explained purely in terms of posture or biomechanics. In traditional biomechanics, muscles are motors that move levers, and by analyzing the forces produced by the motors, we can analyze how movement takes place, gauge movement efficiency, and suggest ways to make it more efficient. We can also see it in terms of support around a vertical axis.

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But human movement is actually far more complicated than this because we are not just muscles and motors but a complex locomotor system that must maintain balance and two feet while retaining mobility and freedom to move. To balance on two feet, muscles have to maintain the body in an upright arrangement, but in such a way that the system is still completely mobile. The solution nature found to this problem was to place the head on top of the vertically-poised spine, but in such a way that the head counterbalances the muscles at the back of the neck, the spine acts as a lengthening device for the muscles of the back, and the muscles of the legs stabilize the struts of the legs but remain lengthened by the struts. This way, the entire structure is maintained upright, but at the same time, muscles are lengthened (rather than tense or constricted) and joints are supported but movable so that the entire structure is mobile. The structure is then able to lengthen or support itself against gravity, and at the same time it is free and movable, and this is accomplished by the dynamic relationship of bony structures--in particular, the relationship of the head which counterbalances the neck muscles, and the spine, which lengthens against gravity as muscles act on the spine. 

 

Does this structure support from the ground up? Yes, we support from the ground up because we have to apply force to the ground to come up off the ground. But to do this the body must also be organized from the top down, because it cannot maintain lengthened and efficient support against gravity unless the head is counterbalanced on top of the spine and the spine lengthens--that is, unless the head leads and the spine lengthens. So the structure is supported from the ground up but organized from the top down. Biomechanically and posturally we are supported from the ground up; dynamically we support from the top down because the system cannot maintain efficient length in muscles unless it lengthens with the head counterbalancing the flexors and extensors and the spine lengthening.