The significance of closed kinematic chains to biological movement and dynamic stability.

Closed kinematic chains (CKCs) are widely used in mechanical engineering because they provide a simple and efficient mechanism with multiple applications, but they are much less appreciated in living tissues. Biomechanical research has been dominated by the use of lever models and their kinematic analysis, which has largely ignored the geometric organization of these ubiquitous and evolutionary-conserved systems, yet CKCs contribute substantially to our understanding of biological motion. Closed-chain kinematics couple multiple parts into continuous mechanical loops that allow the structure itself to regulate complex movements, and are described in a wide variety of different organisms, including humans. In a biological context, CKCs are modular units nested within others at multiple size scales as part of an integrated movement system that extends throughout the organism and can act in synergy with the nervous system, where present. They provide an energy-efficient mechanism that enables multiple mechanical functions to be optimized during embryological development and increases evolutionary diversity.

Fascial hierarchies and the relevance of crossed-helical arrangements of collagen to changes in shape; part II: The proposed effect of blood pressure (Traube-Hering-Mayer) waves on the fascia.

Periodic changes in arterial pressure and volume have long been related to respiratory and sympathetic nerve activity (Traube-Hering-Mayer waves) but their origins and nomenclature have caused considerable confusion since they were first discovered in the eighteenth century. However, although they remain poorly understood and the underlying details of their control are complicated, these waves do provide valuable clinical information on the state of blood pressure regulation in both normal and pathological conditions; and a correlation with oscillatory motions observed by certain practitioners suggests that they may also have some physiological value that relates to changes in the volume of fascial 'tubes'. Part I of this paper (Scarr, 2016) described a complex fascial network of collagen-reinforced tubular sheaths that are an integral part of muscle structure and function, and continuous with 'higher-level' fascial tubes surrounding groups of muscles, the limbs and entire body. The anisotropic arrangements of collagen fibres within the walls of these tubes reflect the most efficient distribution of mechanical stresses and have been considered to coordinate changes in shape, and a proposed link between cyclic variations in arterial pressure and volume, and the behaviour of these fascial compartments is now described.

Fascial hierarchies and the relevance of crossed-helical arrangements of collagen to changes in the shape of muscles.

Muscles are composite structures consisting of contractile myofibres surrounded by complex hierarchies of collagen-reinforced fascial sheaths. They are essentially flexible cylinders that change in shape, with the particular alignment of collagen fibres within their myofascial walls reflecting the most efficient distribution of mechanical stresses and coordinating these changes. However, while the functional significance of this crossed-helical fibre arrangement is well established in other species and in different parts of the body, relatively little attention has been given to this within the fascia of humans; and the relevance of this geometric configuration to muscles and surrounding fascial tissues is described.

Simple geometry in complex organisms.

SUMMARY: Many cultures throughout history have used the regularities of numbers and patterns as a means of describing their environment. The ancient Greeks believed that just five archetypal forms--the 'platonic solids'--were part of natural law, and could describe everything in the universe because they were pure and perfect. The formation of simple geometric shapes through the interactions of physical forces, and their development into more complex biological structures, supports a re-appreciation of these pre-Darwinian laws. The self-assembly of molecular components at the nano-scale, and their organization into the tensegrities of complex organisms is explored here. Hierarchies of structure link the nano and micro realms with the whole organism, and have implications for manual therapies.