Why? The Science of Athletics

130 WHY?-THE SCIENCE OF ATHLETICS Muscles are not so excitable as nerves, but the passing of 280 messages a second along a nerve raises its tempera– ture through electro-chern.ical change one fourteen– thousandth part of a degree. When we raise the tem– perature of the body all the vital processes go on more quickly, and by even a single muscle-twitch the tempera– ture. of the muscle involved is raised about 3/Ioooths of a degree centigrade, and, as we have seen earlier in this book, a muscle movement is made up of a great many muscle-twitches fusing together. Nor is this all, for heat is not produced only by the contraction of the muscle but for a long time afterwards. The activity, as represented by contraction, is followed by recovery, as represented by relaxation of the muscle substance, and It times as much heat is liberated during recovery as during contraction. Now the informal limb€ring-up movements involve a great number of contractions and relaxations of the muscles which are thus quickly warmed up to serve our needs. Limbering-up also increases the heart-rate, and once oxygen has passed through the lungs and into the blood– stream it is carried round the system at a fairly high speed, with the result, as we shall see presently, that there is rapid elimination of carbon dioxide and an appreciable increase in the depth of tidal breathing. It may be, too, that some form of molecular re'arrangement takes place in the muscle-substance during activity which gives it a greater working capacity, but that theory has yet to be proved. What we do know is that oxygen increases effi– ciency, probably by delaying fatigue, wherefore it follows that a man, by limbering-up, increases both his efficiency and his powers of resistance, although to the thoughtless and the uninitiated alike he ·may appear to be doing a foolish thing by, as they say, "exhausting himself" before ever his event is called on. It is all so simple and so logical really, for no motorist, who cares for his car, would take it out on a C<?ld day before he had run the engine for some time to warm it up. This process gives better corn· bustion, besides making the oil less viscous, and there is