Why? The Science of Athletics

if g8 WHY?-THE SCIENCE OF ATHLETICS vein carries away carbon dioxide and other waste– products produced by muscular activity. The nerve, of course, conveys the impulse, or order, which causes the muscle to contract. Each fibre has at least one motor nerve and a good supply of blood-vessels. From the foregoing we see that the arteries supply the muscle with food and oxygen, the veins carry away the waste, while the nerves, .originating generally in .the spinal column and -terminating in nerve-endings on the muscle, convey the orders for the contraction causing the muscle to move the bone to which it is attached. The elementary unit of muscular contraction is a twitch, one twitch occurring when one order is received by way of a· nerve. But creating single twitches, except by electrical stimulation of an isolated muscle, is just about as difficult as firing single shots from a machine– gun. Muscular activity in ordinary life is brought about by prolonged contraction, just as superiority of machine– gun fire is established by sustained bursts of firing. From this it follows that our voluntary activity is created by the sending of a rapid succession of orders along the nerve-path, thus causing the elementary twitches to fuse rapidly together. As you can see for yourself, by placing one hand over the biceps muscle and then ·flexing the arm, a muscle shortens and broadens out when it is contractecL and this causes it to exert a pull upon the bone to which it is attached by its tendon. If the muscle is not allowed to shorten, by the opposition of anothe~ and antagonistic muscle or the weight of something too heavy for it to move, then it-becomes rigid and the limb remains fixed. The contractile ability of ·the muscle is its m~in pro– perty, but although it broadens and becomes shorter when contracted and apparently grows "bigger", careful experiments with isolated muscles have proved conclu– sively that the volume of the muscle does not increase by contraction. Equally careful measurements made of a working limb, however, indicate a total increase in