Why? The Science of Athletics

MECHANICS AND LEVERAGE 297 departure is incorrect, the application of force cannot attain its maximum power, because it will not be applied in the right direction. For example, the angle of applied force is 53 degrees when the sprinter has his spine parallel to the track, but is considerably lessened when he drops his buttocks to a lower level. Diagram B illustrates this principle when the runner is actually coming out of the holes. The applied force, sh6wn in the diagram, represented only a portion of the mean force of the drive in magnitude and direction, working through the centre of gravity, at the moment of departure. The amount of force available is represented by the distance ac, c representing the spot at which the sprinter's forward knee rested upon the track when he was in the "set" position. The application of the pro– pelling force is also shown in Diagram B. Factors Determining Running Efficiency So far we liave considered only sprinting. The laws of mechanics, however, govern bodily efficiency in all forms of athletic activity, and muscle force is continually transmitted to the bones, which act as levers and give mechanical advantage either for force or speed, unless, of course, the levers happen to be of the Class I balancing type. How Leverage Reacts in Running. We have spoken already of the various classes of the human levers and have seen something of their functions. Now let us examine a few of them. The ankle falls into two classes, for its flexors, arranged PWF*, make it a 2nd class lever, while its extensors (FPW) make it a 3rd class lever. Upon the other hand, the FPW arrangement denoting 3rd class leverage ap-plies to the extensors, adductors and flexors of the thigh. In the same way, the action of the leg swinging backwards and forwards like a pendulum in the hip-socket becomes a 3rd class lever under the pull of the hip muscles. This being so, it at once becomes obvious that we have here * F = fulcrum. P = power. W = weight, or resistance.