PEBA foam
Evidence: moderate
The light, resilient, supercritically foamed midsole behind the super-shoe generation. The foam, more than the plate, does the work.
PEBA, polyether block amide, sold under the trade name Pebax, is the midsole material behind the modern super-shoe. It is a tunable block copolymer that is lighter and more resilient than the EVA used in older shoes, and it is the foam, more than the carbon plate, that delivers the performance gain (Healey & Hoogkamer 2021).
Independent testing puts forefoot energy return for the leading super-foams near 78 to 80%, against rough industry figures of 60 to 65% for EVA (RunRepeat foam testing). These numbers are directional rather than precise, and brands rarely disclose the actual polymer. Independent material analysis indicates the marketing names map to different chemistries: Nike ZoomX is supercritical PEBA, Saucony PWRRUN PB is expanded PEBA beads, Asics FF Turbo is PEBA, while adidas Lightstrike Pro is a different polymer, a thermoplastic polyester elastomer (foam chemistry analysis).
What unites the generation is less the specific polymer than the process: supercritical foaming, in which gas is dissolved into the polymer under pressure and released to create a fine, uniform cell structure (foam chemistry analysis). This, combined with a thick stack and the right geometry, is what lets the midsole compress and return energy efficiently under load.
The trade-off is durability. The low-density foams that perform best when new also degrade fastest; see shoe foam durability.
What it means when buying
Buy the package, not the polymer
What delivers the benefit is the whole midsole, the foam, its density, the stack height and the geometry, working together, not the polymer name on the box. Marketing names do not map cleanly onto chemistry, and a shoe with a fashionable foam can still feel worse to you than one without. Judge a shoe by how it feels and runs for you, the comfort-filter principle from running shoes, not by its foam’s branding. And remember the foam’s edge is brightest when new and fades with mileage, so reserve the best foam for racing.