Let ' s stop saying that a muscle ‘ contracts ’

نویسنده

  • Brian Freeman
چکیده

An argument is presented for discontinuing the term ‘contraction’ when describing the so-called active state of muscles and replacing it with a neutral term such as ‘hardening’. The opposite state of the muscle would be called ‘softening’. Hardening as a so-called active state of a muscle may be accompanied by lengthening, shortening, or no dimensional change in the anatomical muscle, depending on the distribution of internal and external forces. All forces in muscles are distributed between two dominant components: discontinuous carneous (fleshy) fibres and continuous collagenous fibres. The viewpoint in this article re-invigorates the old hypothesis that the fleshy component of a muscle works by its cells tending to expand laterally; the laterally-directed stresses are conveyed to the continuous network of collagen and thus to tendons and bones. Shortening in the anatomical muscle is a consequence of the fleshy fibres maintaining a constant volume when hardening and the lateral forces being relayed to the collagen; lengthening of a muscle could be due to both softening of the fleshy fibres and a decrease in the viscosity of the collagen. The organs of movement Since the time of Erasistratos (ca. 290 BC), muscles have been identified as the unique, active components of the movement apparatus [1]. Vesalius (1514-64) commented in his De Humani Corporis Fabrica (1543): "...the flesh of muscles, which is different from everything else in the whole body, is the chief agent, by aid of which (the nerves, the messengers of the animal spirits not being wanting) the muscle becomes thicker, shortens and gathers itself together, and so draws to itself and moves the part to which it is attached, and by help of which it again relaxes and extends, and so lets go again the part which it had so drawn" [2, p. 70]. For decades students have approached the phenomena of muscular action through the disciplines of anatomy, or physiology, or biochemistry. Today the study of muscular function is concentrated in two broad, but essentially divorced, fields. On one hand, macroscopic movements and their electromyograms (EMGs) as determined in the living body are studied in the discipline of kinesiology (i.e.,

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تاریخ انتشار 2016