The elastic potential energy stored is given by the integral of this expression with respect to :

The elastic potential energy per unit volume is given by:

The objective of optimization is to minimize the component's elastic energy.

This type of stored energy is elastic potential energy.

In running there is a conversion between kinetic, potential, and elastic energy.

For example, an arrow gets the elastic potential energy from the bow.

Now elastic potential energy is energy of position and does not change based on a given position.

So how is this loss in elastic potential energy accounted for?

In the human example, suggesting that muscles have elastic potential energy is a bad assumption.

Tendons served to store and release elastic energy during running but were not needed for ordinary walking.