The Enko shoe is a high-tech running shoe, developed by French runner Christian Freschi, that is equipped with a pair of coil-sprung shocks on each shoe in addition to a hinged second sole. This makes it significantly different from all those running shoes that have shock-absorbing cushions which absorb energy on the downstep before releasing it on the upstep.
The shoe's performance is pretty amazing, but the mechanism behind it is pretty simple. As runners stride forward and transfer their weight towards the ball of their foot, their shocks expand and the energy from the coils helps push the foot up and forward.
The shoe is also designed to absorb potentially injury-causing impact upon contact. What's great about the Enko shoe is that it is designed to improve performance but also takes into account safety implications.