We can command our big muscles and they usually obey, but not always; and they often work on their own. You can stop your muscles of respiration, but not for long, and they keep up their motion throughout life with usually no attention from you. Also you would be a poor ball player if you thought out all your motions. Quick skillful motions are automatic.
Striated muscle tissue is "flesh," and in man it constitutes approximately 50 per cent of the weight of the entire body. If you wish to see how the fibers appear, look at a piece of cooked corned beef that has not been cut across, but has been teased out.
Despite all the modern gadgets and labor-saving devices, practically all of us have to use our muscles. It is important to understand how to use them in an efficient manner. Muscles do their work by contracting; that is, by shortening. If a muscle shortens quickly, it has to use more energy to move a certain load. If it shortens slowly, the time in which it is expending energy is increased. For continued, efficient work the trick is to learn the happy mean.
A few people see an illustration of this trick in the performance of their automobiles. Every engine has a definite speed at which it works best. Below this it does not move smoothly. Above this, resistance builds up with wasting of fuel. Of course with muscles or motors it does not follow that this ideal speed is best for practical purposes. Time is valuable as well as energy. I am not offering this as an excuse for reckless drivers in city streets. Life, limb, and auto bodies are also valuable.
It may be a decided advantage for muscles to move slowly. They have two chief tasks: to make motion and to hold position and the same muscles may have to take on both jobs. As our physiologist friend says: "It might be very nice if we could move our arms a hundred times more quickly; but not if the consequence was that we could not hold them out horizontally for more than a second."
Of course, what muscles can do depends on many factors: their size, their manner of construction, and the material of which they are composed are the more important ones. Their normal function varies incredibly. Thus it has been said that the wing muscles of a gnat (insects so small that the Indians called them no-see-ums) can perform a motion in a thousandth of a second; a hummingbird in a hundredth; and the swimming muscle of a whale in a full second.
Not only have the muscles themselves counted, but also the skill with which they are handled. Consider the whip action with which a big league pitcher accumulates speed. As his leg, lifted high in the air, comes down, it speeds the body forward; the shoulder muscles speed the arm; the muscles across the elbow accumulate; the snap of the wrist smoothly adds on and finally the finger tips are traveling at the speed with which the ball leaves. This has been estimated at over 120 feet a second - a ninth of the velocity of sound.
A physiologist who has read the Book of Judges tells how Gideon selected three hundred men from his army of thirty-two thousand and conquered the Midianites. He sent home twenty-two thousand who were "fearful and afraid." Then he dismissed all who bent on their knees to drink, keeping those who lapped water from their palms. The ways of those primitive people were strange. I would have picked those limber enough to have bent their knees to quaff liberally from the stream.
Our scientist has a similar test for a modern army in a modern building. He would first have got rid of the twenty-two thousand fearful and afraid of exercise, who would have waited for the elevator to take them down two floors. The remainder he would have marched down into a subway, and have chosen the three hundred who ran up the escalator, "improvident of energy and impatient of delay."
Most people believe that physical fitness helps in resistance to infectious disease. There is practically no good evidence to this effect. Before the days of antibiotics the finest athletes might succumb to pneumonia as promptly as any weak-looking little specimen.
In a state of nature the demand for physical exercise is satisfied as instinctively as the demands imposed by hunger, thirst, and cold. Perhaps the best demonstration that you can get in so-called civilized life is that of school children at play. They are young animals. Observe how after a short period of imposed inactivity they just have to move violently about. But modern life interferes with this exercise. I saw recently the cynical remark that we spend five thousand dollars a year to provide a bus so that our children may not have to walk to school and fifty thousand dollars so that they may have a gymnasium where they can get exercise.