our gain in strength is only as 10 to 6.6; our power is increased by
only one-third. Now this has an important bearing on the problem we are
going to investigate, for the weight of our body falls on the foot, so
that only about one-third of the lever--that part of it which is formed
by the heel--projects behind the point on which the weight of the body
rests. The strength of the muscles which act on the heel will be
increased only by about one-third.

We have already seen that a double engine, made up of the
_gastrocnemius_ and _soleus_, is the power which is applied to the heel
when we walk, and that the pad of the foot, lying across the sole in
line with the ball of the great toe, serves as a fulcrum or rest. The
weight of the body falls on the foot between the fulcrum in front and
the power behind, as in a lever of the second order. We have explained
why the power of the muscles of the calf is increased the more the
weight of the body is shifted towards the toes, but it is also evident
that the speed and the extent to which the body is lifted are
diminished. If, however, the weight be shifted more towards the heel,
the muscles of the calf, although losing in power, can lift their load
more quickly and to a greater extent.

We must look closely at the foot lever if we are to understand it. It is
arched or bent; the front pillar of the arch stretches from the summit
or keystone, where the weight of the body is poised, to the pad of the
foot or fulcrum (Fig. 6); the posterior pillar, projecting as the heel,
extends from the summit to the point at which the muscular power is
applied. A foot with a short anterior pillar and a long posterior pillar
or heel is one designed for power, not speed. It is one which will serve
a hill-climber well or a heavy, corpulent man. The opposite kind, one
with a short heel and a long pillar in front, is well adapted for