Why? The Science of Athletics

MECHANICS AND LEVERAGE 299 of the pendulum may, I think, be made to illustrate the point, for the shortening of its length makes it swing faster, and, equally, the leg recovers more rapidly when the knee is bent. When a long and strong push from the rear is required, however, it is necessary that the runner's leg b.e fully straightened, and for quick recovery the knee must be sharply flexed. It is the strength of the quadriceps in straightening the leg, combined with the use of the plantar muscles of the sole of the foot and the calf muscles, which supply most of the force for running. A further example of leverage is found in the extension of the foot as the toes are thrust down against the track. This is shown clearlyinDiagramD. Theweight, which must be carried forward of the point of resistance at the ball of the foot, is indicated ; the fulcrum is at the ankle, and the power is supplied by the gas– trocnemeus and soleus muscles of the calf. Musclep__u/1 1 F afank1e DIAGRAM D In this connection it may be noted that a foot with a low arch is probably deficient in spring and pushing strength, whereas it has been calculated that the con: tractile force of well-developed calf muscles is at least 1200 lbs., and it follows that the more highly the calf muscles are developed the better will be the results attained. The ankle, knee and hip-joints are extended in much the same way that a compressed spring uncoils, and here again we have an analogy to show us how power may be multiplied. Referring back for a moment to the opening para– graphs of this chapter and remembering what has been said elsewhere in this volume in relation to the viscosity of muscles, it must be borne in mind that what we are