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MECHANICAL ACTION OF MUSCLES

There is also a mechanical process that takes place in every kind of muscular work, for when the muscle contracts, its mass is condensed, and the soft parts near the muscle are exposed to a very strong pressure.

This fact has a very important bearing upon the veins and the lymphatics, and upon the fluids which these vessels carry to the heart.

While the heart principally controls the action of these vessels, much aid is afforded them by the temporary pressure of the contracted muscles, and thus we see that exercise stimulates and increases the circulation in the veins and lymphatic vessels.

But these are not all the results that are produced by proper exercise. In voluntary muscular action, as a rule, one or two joints are set in motion.

These joints are protected, to prevent their bony surfaces from coming in contact with each other. While the motion is a rubbing or friction movement, exercise properly taken is free from all danger; moreover, the joint is decidedly benefited by such action, nutrition to the part being increased.

Generally, where the muscles are attached to the bones large processes or elevations are found; and the greater the muscles the larger the processes.

This must indicate an increased nutrition to the bone, as well as increased strength to the osseous system.

The effect of exercise is not only chemic and mechanic, but also physiologic.

The voluntary movements are what distinguish animals from plants.

The higher we go in the scale of animal life, the more perfect is the mechanism for executing the various movements necessary to its existence. We find a finer muscular development in connection with a more highly developed nervous system.

Involuntary motions are adjusted by the sympathetic nervous system, while the voluntary movements are controlled and regulated by the cerebro-spinal nervous system.

That mysterious power which we call will imparts, at times, an impulse to muscular activity, and at others it restrains and impedes it.

Whatever the nature of the will, we know that when an impulse is generated in the brain it is carried to the nerves of the spinal cord, and from them to the peripheral nerves, and thence to the muscles, which causes what we call contraction.

Thus we see that exercise is not so simple a thing as is commonly supposed, but, on the contrary, it is a complex process involving the brain, the spine, the nerves, and the muscles.

As the activity of a muscle produces a constant change in the circulation, so this same action will

greatly influence the substance of the nerves themselves.

This applies only to motor nerves, although some authors claim that exercise has an indirect effect upon the central nervous system.

At times physicians employ certain remedies called derivatives, the object of which is to relieve certain parts of the body. For instance, by the use of purgatives, to relieve portal congestion or to remove a sluggish circulation in the brain. In some mental disorders, as in melancholy or hysteria, the same theory directs that the mind should be constantly employed, so that the patient may have no time to think of himself.

Again, when there is a disturbance in the normal condition of the motor nerves, as in spasms, it may be removed by a strong and decided impression upon the central nervous system through sorrow, sudden terror, etc., or by an impression upon the nerves, by burning.

When there is any disturbance in the central nervous system, we can often, by employing agents to act upon the motor nerves, remove its cause.

We reach this conclusion because persons suffering from irritation of the central nervous system are generally those who use their motor nerves but little. Again, it is a common experience for the well-trained masseur to see these patients improve very rapidly, and be finally cured by fixed duplicated active movements.

Thus we conclude that active movements have a beneficial effect upon the nervous system, direct upon the motor nerves, and indirect, upon the central nerves.

What we have said about the effects of the movements has been of a general character, but it is necessary to understand the local effects upon the different organs of the body.

When treating a local affection, the movements or manipulations are to be applied in such a way that the affected part will derive the benefit. When the circulation is feeble in certain parts, the muscles in the neighborhood must be made to act, so that the blood will circulate more freely in the part diseased.