The energy used in making the footstep is used to push the mud/gravel/sand etc. out of the way (hence it's harder to run on sand as it takes more energy) and to propel the animal forwards. It all ends up as heat eventually; the particles of sand moving against each other generate friction, and therefore heat, and stop (otherwise they would move indefinitely).
That's frictional energy, I am talking about the impact energy.
Say you jump up and down on the spot, where does that energy go from your impacts?
To say the universe has a start and end is a oxymoron, otherwise what would you call the universe before the so called big bang?

I personally think it just kicked off, in this little patch of the universe all them billions of years ago. A few black holes having a punch up etc. That's if the things exist.

To me the universe is a massive fractal, its the only explanation.
