Alphafly 4 launches with ZoomX LT foam Nike calls 17% lighter
Believe in the Run got a first look, but nobody outside Nike's testing program has raced in it yet.
The Nike Alphafly 4 is out, launching in limited numbers on September 17, 2026, with broader availability on October 29. Believe in the Run says the initial release is at Nike only. Posters on r/RunningShoeGeeks flagged both the Nike Newsroom announcement and the shoe going live on the Nike UK site the same day.
The change that matters is under the foot. Believe in the Run says the Alphafly 4 debuts an updated, lightened ZoomX LT, which Nike says is as much as 17% lighter than the original compound while returning in the neighborhood of 8% more energy. Nike tuned it to be softer and bouncier.
What actually changed
Look at it quickly and it reads like the Alphafly 3. Believe in the Run says the spec sheet tells another story, with Nike claiming just about everything is new. The sock-like Atomknit upper has been refined to fit even more like a sock, the Fast Shot outsole is placed for traction in the rain, and the Air Zoom units are as visible as they have ever been. The carbon Flyplate keeps its signature scoop.
Believe in the Run frames the whole thing as a response to the adidas Adizero Pro Evo 3 breaking the two-hour barrier in the marathon, which it says sent Nike back to the lab.
What it actually means
This is a first look, not a review. Believe in the Run says only one of its testers, Meg, got a pair early as part of Nike's testing program, so nobody else on the site has run in it. No independent tester has put it through a marathon build, and the number everybody actually wants, a verified weight in a men's 9, has not been published. Nike's 17% and 8% figures are Nike's own numbers for the foam compound, not a measured weight for the finished shoe.
So treat the foam claims as claims for now. The interesting test is whether the lighter ZoomX LT holds up over 26.2 miles the way the old stuff did, and that answer arrives when the fall marathon results and the first proper reviews land.
This isn't your grandpa's ZoomX anymore. The Alphafly 4 marks the debut of an updated, lightened ZoomX LT, which is as much as 17% lighter than the original compound while offering in the neighborhood of 8% more energy return.
Nike is launching the Alphafly 4 in limited capacity on September 17, 2026 with broader availability coming on October 29 .
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