Some of these are shown in Fig. 8. The foot, then, is a
lever of a very remarkable kind; all the time we stand or walk, its
rigidity, its power to serve as a lever, has to be maintained by an
elaborate battery of muscular engines all kept constantly at work. No
wonder our feet and legs become tired when we have to stand a great
deal. Some of these engines, the larger ones, are kept in the leg, but
their tendons or piston cords descend below the ankle-joint to be fixed
to various parts of the arch, and thus help to keep it up (Fig. 8).
Within the sole of the foot has been placed an installation of seventeen
small engines, all of them springing into action when we stand up, thus
helping to maintain the foot as a rigid yet flexible lever.
We have already seen why our muscles are so easily exhausted when we
stand stock-still; they then get no rest at all. Now, it sometimes
happens in people who have to stand for long periods at a stretch that
these muscular engines which maintain the arch are overtaxed; the arch
of the foot gives way.
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