Muscular energy

“ A comparison between the muscular and the nervous systems from the point of view of their connection with heat is a bold one for many reasons. Between nerve and muscle there exists this enormous difference—that the former is endowed with a spontaneity denied to the latter. Muscular fibre never contracts of its own accord; it needs a stimulus—its energy is borrowed. The nerve-cell, on the contrary, has in itself an ever-present, never-exhausted power of action, of which the energy is its peculiar property. ”

“ So, again, when muscular contraction does not result in motion, as when one tries to raise a weight too heavy for him, the energy which would have appeared as work, takes the form of heat: a result deducible by the law of correlation from the steam-engine.
The last of the so-called vital forces which we are to examine, is that produced by the nerves and nervous centers. In the nerve which stimulates a muscle to contract, this force is undeniably motion, since it is propagated along this nerve from one extremity to the other. ”

“ There is also a great lesson here in the law of supply and demand;—when the body is at mental or muscular work, the potential energy liberated leaves through muscle or brain, as energy, and is expressed in the result of the work; when the body is at rest, it leaves it as heat (excepting such part as is necessary to carry on metabolism, circulation, etc.) If much muscular energy is called for, a deep, full breath is instinctively drawn to supply the oxygen necessary for the added force required. ”

“ He considers that a muscle is a machine for the conversion of potential energy into mechanical force; that the mechanical force of the muscles is derived chiefly, if not entirely, from the oxidation of matters either contained in the blood or deposited around the muscular fibres, and not from the oxidation of the muscles themselves; that in man the chief materials used for the production of muscular power are non-nitrogenous ”

“ It may be true, it certainly is true, that if an individual's energies are concentrated in the direction of development of one system of the body, the other systems to some extent suffer. A great and constant devotion to the development of the muscular system will produce very powerful muscles, and great muscular energy, with a strong tendency to, and pleasure in exercise. ”

“ The prodigies of force that astonish us are due to a very simple cause, and can be accounted for under the common law that, of two muscles having the same mass and the same energy, the shorter one is capable of raising the more considerable weight. We may figure muscular fiber as a spiral spring, habitually relaxed, which, under nervous action, flies back upon itself. ”

“ The energy of muscular contraction comes from the breaking down of non-nitrogenous components of the muscle, and perhaps in some measure from the decomposition of nitrogenous constituents. Further, there is a liberation of heat, a development of lactic acid, etc. ”

“ Like a bent spring the muscle contains a certain amount of potential energy, which the will can use at pleasure; but when the supply is once exhausted, when the spring has lost its tension, a further supply of force from without is necessary before more work can be performed.
These facts furnish an important clew to the source of muscular power. The experiments of Voit and Pettenkofer show that while storing up oxygen during rest the organism is laying up a store of force to be used later ”

“ This fact was immediately accepted by many physiologists as a proof that the commonly received view of the source of muscular power was incorrect, and that that power was in reality derived from the non-nitrogenous components of food—its fat, starch, sugar, etc. According to them, the muscles are, like a steam-engine, simply an apparatus for the transmission of energy furnished by some other substance, while the fat, etc., is the fuel of the living machine. ”

“ This, too, is of continual service to every active animal. By it information is given as to the energy of contraction of the muscles, and of the amount of [245] movement effected—not to mention the rapidity and duration of the muscular effort. By it the position, or changes of position, of the motor-organs are indicated. It is obvious, therefore, that the sensations obtained in this way, some of which are exceedingly delicate, are an important guide to the organism in the putting forth of its activities. It is through the muscular sense that we maintain an upright position. ”

“ There is no question that the energy of muscular contraction can come from all three classes of organic foodstuffs. Voluntary muscular movement is under the control of the nervous system, and when the stimulus is applied the muscle is bound to contract, provided of course there is sufficient energy-containing material present to furnish the means. ”

“ A liquid surface contains a quantity of energy equal to its surface tension multiplied by its area, hence any variation either of area or of tension corresponds to a variation of its energy. This novel conception constitutes a valuable addition to the experimental study of the physiology of muscular action, since it gives us some idea of the mechanism by which chemical energy may be transformed into muscular contraction. ”

“ And so, when we attempt for the first time any muscular act, we expend a great quantity of superfluous energy which we learn gradually to subdue. By exercise certain movements are fixed, to the exclusion of others. ”

“ Indeed, all that I want to bring about muscular contraction is, not a metamorphosis of muscle which issues in the development of muscular force, nor a transformation of heat into muscular force, but simply a supply of electricity during the state of muscular inaction which will counteract the tendency which the muscle always has to contract as an elastic body. ”

“ The muscles are like the various bits of machinery which go to make up a steam engine. In performing their work they produce heat and motion. The fuel which supplies this force is taken into the body as food, prepared for use in the intestinal tract, and from there carried by the blood to be stored up in the muscles and various tissues as latent force. Through the circulation of the blood the whole body is heated by muscular exercise. It stands to reason that continual exercise of a certain kind will develop certain muscles. ”

“ Mountains are to the rest of the body of the earth, what violent muscular action is to the body of man. The muscles and tendons of its anatomy are, in the mountain, brought out with force and convulsive energy, full of expression, passion, and strength; ”

“ Both evidently derive the principle of the activity that marks them from the same external and internal media; but, while the muscle, a mechanical organ, is limited to the obedient transformation of the force assigned to it, under the form of heat, into a measurable amount of work, the nerve, a vital organ, remains impenetrable and inaccessible to our calculations, and exerts its characteristic and sovereign powers in its own way, through a series of operations that escape all estimates of their force and heat. On the part of the muscular system, every thing can be measured ”

“ Fig. 112—Muscle cells from the heart, highly magnified (after Schäfer) . The Muscular Stimulus.—The inactive, or resting, condition of a muscle is that of relaxation. It does work through contracting. It becomes active, or contracts, only when it is being acted upon by some force outside of itself, and it relaxes again when this force is withdrawn. Any kind of force which, by acting on muscles, causes them to contract, is called a muscular stimulus. Electricity, chemicals of different kinds, and mechanical force may be so applied to the muscles as to cause them to contract. ”

“ Of course this possibility of variation is of great advantage in our use of our muscles. It depends upon the very large number of individual fibers of which even our smallest muscles are made up. Whenever any single fiber contracts, it pulls to its full extent; if only a few become active, the pull of the whole muscle will be slight; as more come into action, more force will be exerted; the muscle will show its utmost power when all the fibers are contracting at once. We are conscious of greater mental effort when we make a powerful muscular contraction. ”

“ They all tell of chemical changes in muscle, and they all support the statement that the harder the muscle has to work, the greater is the activity of the chemical phenomena happening in it. Let us put this in more correct scientific language. The setting free of energy by the muscle,—as mechanical energy when it moves, and as heat when it becomes warm,—is associated with, and is likely the result of, the chemical processes happening in it. ”

“ It is a familiar fact that all muscles become larger and stronger through exercise; but the reason why they so increase is not such a simple matter. The vitality of muscular, and indeed of all other living tissue, is strangely under the influence of the nervous system. ”

“ In this concatenation of the several forces of nature, physical and vital, the force acting in a nerve may also be correlated with chemical force, with the heat developed in the muscle, and even with the peculiar molecular motions which produce muscular contraction and all its accompanying physical and mechanical consequences. ”

“ The well-trained muscles contain only healthy protoplasm, and give off but a small percentage of nitrogenous decomposition products. Let the well-fed person who takes but little exercise, run half a mile, or play a simple game of ball, and the following day the muscles will be stiff and sore; this unusual exertion has caused the breaking down of much loosely organized tissue which could have been made firm and healthy by daily muscular activity. ”

“ It necessitates careful diet and constant exercise for a long period, and proves equally beneficial to both sexes. This book has been written in vain if the reader has not grasped by now that the activity of the muscles implies the activity of all the organs in the body. Accordingly, the whole muscular system is by appropriate methods given frequent exercise: gentle at first; never exhausting; but constantly increasing as the strength grows. The result is a general development of the organs throughout the body, which will in time work a complete metamorphosis in the individual’s physique. ”

“ The muscles should be used, in order that the size and strength of these organs may be adequate to the demand made upon them. It is a law of the system that the action and power of an organ are commensurate, to a certain extent, with the demand made upon it; and it is a law of the muscular system that, whenever a muscle is called into frequent use, its fibres increase in thickness within certain limits, and become capable of acting with greater force ”

“ We saw in last lecture that a muscle is a little laboratory in which chemical processes go on, and that the energy manifested by the muscle depends upon the activity of these operations. If a muscle is constantly throwing off effete matters arising from the wear and tear of its substance, and if it is always expending energy, fresh matter and fresh energy must be supplied to it. ”

“ The elements of the substance to be burnt are torn from each other, and they unite with the oxygen of the air to form simpler bodies. When this occurs, energy appears as heat. Similar phenomena occur in a muscle. The muscle needs oxygen and it needs food stuffs. It builds some of these food stuffs into its own substance, thus always making up for the "tear and wear" that goes on when it works, and it uses some of the others, effecting in some mysterious way chemical changes in them, always splitting them up into simpler bodies.
Let us think of the muscle as a little machine or engine. ”

“ Now every organ in the body is either in itself a muscle or a system of muscles, or is controlled by muscles. That is to say, none of the infinite processes incidental not only to any movement, but to even perfectly passive life, are independent of muscular action, automatic it may be, and unconscious or sub-conscious, but still muscular.
The action of the heart itself, for instance, which is, in ordinary circumstances, entirely automatic and absolutely essential to life, consists in the alternate contraction and expansion of muscle, which sends the blood to all parts of the body ”

“ The muscles thus called into play, are those which are ordinarily under the sway of the will, but which in these cases act through this reflex action of the cord, altogether independently of the will. A healthful reflex activity produces an elasticity, or "tone," of the voluntary muscular system, which, in a great measure, explains the existence in the young and vigorous of a feeling of buoyancy and reserve power. Its possessor is restlessly active, and it may appropriately be said of him, "he rejoiceth as a strong man to run a race." ”

“ Various syntheses like that above outlined are known to take place in the body; and, moreover, all the facts seem to indicate that muscular force originates in a splitting up of some substance in the muscle, accompanied by the liberation of force, rather than by any process of oxidation in the ordinary sense of the word. ”

“ Success in muscle-reading depends upon the powers of the principal and upon the susceptibility of the subject. The latter must be capable of mental concentration; he must exert no muscular self-control; he must obey his every impulse. Under these conditions, the phenomena are in accordance with known laws of physiology. On [Pg 43] the part of the principal, muscle-reading consists of an acute perception of the slight action of another’s muscles. ”