Jason Kerestes is a graduate student at Arizona State University. With support from DARPA, he has developed the AirLegs exoskeleton. It's a small machine worn on the back that decreases the metabolic cost of walking and running by about 10% versus not wearing the machine.
The machine helps people run by pulling on straps located just below the knee and on the shoes. Here is Kerestes demonstrating the second version of AirLegs, which pulls on just the lower legs.
-via Hack A Day