Unlike traditional shoe midsoles made primarily of foams, rubber compounds, or polymers, WaveSpring® technology stores and disburses energy with every step. Testing performed at Michigan State University in 2001 reported that 87% - 96% of the energy is returned from the WaveSpring®. This is the highest energy return score for any midsole material ever tested.** As a result, our footwear not only cushions, but returns energy. In a very real sense, the WaveSpring enables you to recycle your own energy!