As the heel rises, then, it
becomes a more effective lever; the muscles gain in power. The more the
foot is arched, the more obliquely is the heel set and the greater is
the strength needed to start it moving. Hence, races like the European
and Mongolian, which have short as well as steeply set heels, need large
calf muscles. It is at the end of the upward stroke that the heel
becomes most effective as a lever, and it is just then that we most need
power to propel our bodies in a forward direction. It will be noted that
the heel, unlike the crank-pin of an engine, never reaches, never even
approaches, that point of powerlessness known to engineers as a dead
centre. Work is always performed within the limits of the most effective
working radius of the lever. It is a law for all the levers of the body;
they are set and moved in such a way as to avoid the occurrence of dead
centres. Think what our condition would have been were this not so; why,
we should require revolving fly-wheels set in all our joints!
[Illustration: Fig.
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