Wearing a pair of Air Zoom Alphafly NEXT% Eliud Kipchoge successfully ran a marathon (42 km or 26 miles) in under two hours. What is special about the Nike design are the two air chambers made of thick foam that absorb impact vibrations and make the running shoes springier than their predecessors. A carbon fiber plate shaped like an S and running the length of the sole supports this effect and helps the foot roll forward and thus adds propulsion. For the first time this new technology led to the IAAF defining what qualities a running shoe was allowed to have in order to be admitted to a competition. Moreover, since that time models must be on sale in retail outlets for at least four months before they can be worn in competition. The Alphafly was first available on the market after the Kenyan’s world record; however, as the “fastest running shoe” it sold out in only a few hours. Today, a pair still costs almost 300 Euros.