Nike’s Alphafly 4 keeps the brand’s flagship marathon shoe at the center of its racing lineup, but introduces substantial changes beneath a familiar-looking exterior. The updated model weighs 6.6 ounces, has a 39–31-millimeter stack height and an 8-millimeter heel-to-toe drop.
The most significant revision involves the Air Zoom units. Nike now uses radio-frequency sealing instead of the heat-sealing process used on the Alphafly 3. According to the company, the new construction produces thinner seams and makes the units 30 percent lighter and softer.
Nike has also slightly widened the carbon-fiber plate to improve stability and added a new ZoomX-lt/">ZoomX LT foam. The foam uses the same ingredients as the existing ZoomX material but is processed differently to reduce weight and improve energy return.
On the road, the Alphafly 4 feels noticeably softer and more cushioned, particularly under the forefoot. Its Air Zoom units engage with less force, making the shoe more comfortable at slower paces. However, compared with the Alphafly 3, it delivers less snap when running at 10K pace or faster. The Alphafly 3 rewards greater force with a stronger response, while the Alphafly 4 offers a gentler ride without the same explosive rebound.
The upper is another clear improvement. The new AtomKnit design is softer, easier to put on and more accommodating than the notably tight upper of the Alphafly 3. The toe box provides additional volume, allowing more room for the toes to spread—an advantage during longer efforts, when feet can swell.
The reviewer did not race in the Alphafly 4 or complete a full 26.2-mile run in it, so the assessment remains based on shorter testing. Still, the softer cushioning and more comfortable fit suggest that the shoe may be better suited to the later stages of a marathon, when fatigue and reduced running form make comfort increasingly important.
The overall verdict is not a simple upgrade or downgrade. The Alphafly 3 and Alphafly 4 are described as strong shoes with different personalities: the older model is firmer and more responsive, while the new version is lighter, softer and more comfortable. For most marathon runners, the Alphafly 4 may be the preferable option, whereas shorter races may favor a more responsive shoe such as the Vaporfly 4.
Sources: Outside.