Nike launches lighter Alphafly 4 marathon shoe with new foam and air units

Nike has launched the Alphafly 4, its latest flagship marathon racing shoe, claiming it is 5% lighter and delivers 10% more energy return than its predecessor. The shoe features a new ZoomX LT foam and redesigned Air Zoom units made with radio frequency welding, which Nike states are 17% and 30% lighter, respectively. A limited release occurred on September 17, with broader availability scheduled for October 29. Nike stated the Alphafly 4 was fast-tracked for release to be eligible for use at the World Athletics Road Running Championships in Copenhagen. Prototypes of the shoe were worn in races for a world record half marathon and an American marathon record before the public launch. The company emphasized that the development uniquely focused on stability, a benefit it says "trickled up" from everyday athletes to elites. The shoe's updates include a new Atomknit 2.0 upper and a slightly wider carbon-fiber plate to enhance forefoot stability. Nike's VP of running footwear, Bret Schoolmeester, explained that the new manufacturing process for the Air Zoom units uses radio frequency vibrations instead of heat, resulting in a lighter plastic.