ZoomX: Nike's Supercritical Pebax Racing Foam
What ZoomX is
ZoomX is the trade name Nike uses for its highest-performance midsole foam. The midsole is the cushioning layer between the outsole (the rubber that touches the ground) and the upper (the part that wraps your foot). ZoomX is built from a material called Pebax, a polyether block amide that sits in the family of thermoplastic elastomers known as PEBA. Pebax is made by the French chemicals company Arkema and was originally developed for demanding industrial and aerospace uses before it was adapted into running shoe foam.
What makes ZoomX different from an ordinary foam is how it is produced. It is a supercritical foam, meaning the base material is expanded using gas held in a supercritical state, a condition between a liquid and a gas. This process creates a very light foam full of fine, evenly sized cells. The result is a midsole that is unusually soft and springy for its weight.
Why ZoomX matters
The single most useful number for a racing foam is energy return: how much of the force you put into the ground on each footstrike the foam gives back as you push off. Nike states that ZoomX returns close to 85 percent of that energy, the highest of any foam Nike makes and well above the roughly 65 percent typical of older EVA midsoles. Higher energy return means less of your effort is wasted as heat in the foam, which can translate into a faster or more economical run over a race distance.
ZoomX is also very light. Reducing the weight carried on the foot is one of the most direct ways to lower the energy cost of running, because the foot is swung forward thousands of times per mile. A foam that is both light and highly elastic is therefore valuable to a racer.
How ZoomX works
When your foot lands, the foam compresses and stores energy like a spring. A good racing foam then releases most of that stored energy as the foot rolls forward and pushes off. ZoomX is tuned to do this quickly and with little loss. The fine cell structure created by the supercritical process is what gives it this combination of softness on landing and quick rebound on toe-off.
Because ZoomX is so soft and light, it is not very stable on its own. Nike addresses this by pairing it with a stiff carbon fibre plate embedded inside the midsole. The plate stiffens the shoe lengthways, helps the foot roll forward, and stops the soft foam from collapsing sideways. This foam and plate combination is the basis of Nike's Vaporfly and Alphafly racing shoes.
Where ZoomX first appeared
ZoomX reached the public in 2017 in the Nike Zoom Vaporfly 4 percent, the shoe whose name referred to the average improvement in running economy Nike measured in testing. It was the first widely sold shoe to combine a supercritical PEBA foam with a full-length carbon plate, and it began the era of so-called super shoes. ZoomX has since appeared in the Vaporfly line, the Alphafly line, and Nike's top distance spikes.
Benefits
What ZoomX gives a runner
- The highest energy return of any Nike foam, stated at close to 85 percent.
- Very low weight for the amount of cushioning provided.
- A soft landing combined with a quick, springy push-off.
- When paired with a carbon plate, a smooth forward roll through each stride.
Limitations
ZoomX is a racing foam, and its strengths come with trade-offs. It is less durable than firmer training foams, so it tends to lose its bounce sooner and is usually reserved for races and key workouts rather than daily mileage. On its own it is soft and unstable, which is why Nike almost always builds it around a plate. It is also expensive to produce, which is reflected in the price of the shoes that use it.
How ZoomX compares
| Foam | Owner | Base material | Typical use |
|---|---|---|---|
| ZoomX | Nike | Supercritical Pebax (PEBA) | Racing and key workouts |
| React | Nike | Proprietary blend | Daily training |
| EVA | Industry standard | Ethylene-vinyl acetate | Budget and general training |
Other brands make their own supercritical foams that compete with ZoomX, such as Adidas Lightstrike Pro and Saucony PWRRUN PB, both of which also use PEBA-based materials. ZoomX is Nike's entry in that category.
Buying considerations
ZoomX shoes are racing tools. If your goal is a fast time on race day, a ZoomX shoe with a carbon plate offers a real advantage. If you want a single shoe for everyday running, a more durable training foam is usually the better choice, and you can save the ZoomX shoe for races. Because the foam wears faster, many runners rotate a ZoomX racer alongside a sturdier daily trainer.
Common misconceptions
ZoomX is sometimes confused with Nike Air or Zoom Air, which are pressurised air units, not foam. ZoomX is a solid foam material and contains no air bag. It is also not the carbon plate itself; the plate is a separate component that Nike places inside the ZoomX midsole. Finally, a higher energy return figure does not guarantee a faster time for every runner, because fit, form, and fitness all matter as well.
Related terms
To understand ZoomX fully it helps to know a few connected terms. Pebax (PEBA) is the base material. Supercritical foam describes the manufacturing process. A carbon plate is the stiff insert ZoomX is usually paired with. Energy return is the measure of how much force the foam gives back. EVA is the older, firmer foam ZoomX improves upon.
ZoomX at OD's
At OD's Designer Clothing in St Helens we do not stock Nike, but we carry running shoes from other leading brands including On and Saucony. If a ZoomX shoe appeals to you for its supercritical racing foam, Saucony's PWRRUN PB is a comparable supercritical PEBA foam used in Saucony's Endorphin racing range, which we stock. Message us and we will help you choose the right racing or training shoe for your goals. We offer next-day delivery and free click and collect.