[ars]

> If muscles could apply the full force in the fraction of time that feet touch the ground

Or if they could touch the ground for longer. We need human mounted wings to provide some downforce :)

Or more realistically an elastic belt strapped to the runner, and running on a track underneath them.

[garganitan]

Interestingly, you've hit upon the popular hypothesis that flight actually evolved via the wings providing downforce enabling faster/vertical running up trees.

[ajuc]

So, we need longer feet. Or longer shoes.

[bdg]

More legs!

[pwr22]

Maybe some form of spoiler :P?