Tension and Release: The Sol/Gel of Muscle
Excerpted from Deane Juhan’s Job’s Body
As we have previously remarked, one of the most impressive features of connective tissue, the quality that makes it so widely useful as a structuring agent, is its ability to behave like a liquid crystal. It can be watery, elastic, wiry, or solid, depending upon local functions and stresses. It accomplishes this wide range of sol/gel properties in part by varying the proportions of liquid ground substance to tough collagen strands, in part by varying the number of hydrogen bonds which lock the long molecules of collagen together, and in part by investing its matrix with additional substances, like cartilage and bone.
Muscle tissue also displays this liquid crystal quality. We experience its extreme sol state in the passive flaccidity of complete relaxation, and its extreme gel state when it is flexed and hardened. Muscle tissue evolved out of connective tissue, and it accomplishes its variations in softness and hardness in ways that are reminiscent of its precursor. Like collagen strands, muscle cells are quite long and thin, making them like fine threads when they are pliable and like tiny girders when they are stiffened. And like collagen strands, the interiors of muscle cells are composed of extremely long molecules arranged in parallel; these long molecules may be either loosely associated, as in our anaesthetized old man, or locked into one another in a fashion that is similar to hydrogen bonding in collagen fibers, giving the old man's muscles their stiff and hardened feel when he is awake. In both collagen and muscle, it is the varying degrees of loose association and chemical bonding of long, thin molecules which give us the varying qualities of sol and gel.
The major difference is that connective tissue adjusts to its degrees of sol and gel over longer periods of time—the millenia of evolutionary genetic development, the periods of rapid growth, the decades of drying out in the normal aging process, or the months and years of a chronic local strain. Its processes of hardening and softening, shortening and lengthening are relatively slow and conservative.
Muscle tissue, on the other hand, has developed the ability to shift its sol/gel states almost instantaneously to conform to the needs or whims of the moment. It can lengthen, shorten, soften, or harden all at the snap of a finger, creating an ever-changing kaleidoscope of structural conditions and movements. The activities of maturing connective tissue unfold our structure as a species Man; the activities of maturing muscles unfold the innumerable momentary structures that the individual superimposes upon his species—sitting man, standing man, walking man, dancing man, graceful man, awkward man, slumped man, erect man. Muscle is connective tissue that has learned how to quickly lengthen and contract.
Now no matter how soft or hard a muscle may be, or how complicated a coordinated movement, each individual muscle cell has only three options. It can shorten, it can lengthen, or it can lock into place preventing either motion. Yet from these meager choices muscle tissue produces all of the postures, gestures, and qualities of flesh of which we are capable. We stretch, we contract, and we lock into place; this is, in a nutshell, the entire gamut of our motor behavior. What are the arrangements and interactions of the muscle cells and their contents that make these simple miracles possible?
