The Foam Atlas

Modern running-shoe midsoles are built from a handful of distinct polymer families. Each behaves differently underfoot — different weight, different energy return, different durability, different cost. This atlas explains what the chemistry actually is, why it matters for runners, and which shoes in the Next Pair catalog are built on each foam.

Polymer suppliers (Arkema/Pebax, BASF, Dow) and peer-reviewed work describe the chemistry families themselves. Which polymer sits in a given shoe is a separate question: brands publish foam names and performance figures, rarely the polymer — so the per-shoe chemistry here comes from named reviewers and independent teardowns (RunRepeat's cut-in-half lab chief among them). Every shoe-level claim links back to its source. We don't fabricate quotes and we don't take brand money.

The foams

• PEBA / Pebax 48 shoes in the catalog Polyether block amide — Arkema's Pebax — is the chemistry behind every modern carbon-plate marathon racer. Lightest-in-class, springiest-in-class, but pricey and not as durable as EVA.
• A-TPU (aliphatic TPU) 10 shoes in the catalog Aliphatic thermoplastic polyurethane — the foam behind ASICS FF Leap and Puma's NITRO Elite. The chemistry challenging PEBA at the racing tier: springy like PEBA, but holds its bounce far longer.
• TPEE 18 shoes in the catalog Thermoplastic polyester elastomer — the chemistry behind Adidas Lightstrike Pro, Saucony incrediRUN, and New Balance Infinion. A durable, temperature-stable super-foam cousin of PEBA.
• Supercritical foams 66 shoes in the catalog Supercritical (SCF) foaming and nitrogen infusion turn ordinary EVA, TPEE, or PEBA into lighter, bouncier midsoles by replacing chemical blowing agents with pressurized inert gas. Most modern "super-trainers" sit here.
• EVA 72 shoes in the catalog Ethylene-vinyl acetate. The default running shoe midsole foam for forty years — cheap, durable, predictable, but heavier and less springy than the modern alternatives. Still under the marquee daily trainer in your rotation.
• TPU / eTPU 19 shoes in the catalog Thermoplastic polyurethane — BASF's Infinergy is the famous one (Adidas Boost). Heavy but indestructible. Mostly relegated to durable inserts and stability features now that supercritical EVA and PEBA exist, but the chemistry is having a quiet revival.
• Olefin block copolymers 15 shoes in the catalog Polyolefin elastomers — Dow's Infuse OBC family. Used as a blend partner with EVA (ASICS FF Blast Plus) or as a stand-alone (Nike React, On Helion). Energy return between EVA and TPU; durability profile genuinely good.

Brand-foam comparisons

Modern racing foams split across three chemistries — PEBA, A-TPU, and TPEE — and each brand tunes the polymer, the geometry, and the plate system differently. These side-by-side pages cover how specific branded foams behave next to each other, paired shoe-by-shoe across racing and training categories.

• ZoomX vs Lightstrike Pro 24 shoes compared Nike vs Adidas — the two most recognizable racing foams. Vaporfly vs Adios Pro down through plateless dailies.
• Lightstrike Pro vs PWRRUN PB 20 shoes compared Adidas vs Saucony — directive-rocker PEBA vs forgiving-PEBA. Cleanest tempo-day comparison in the matrix.
• FF LEAP vs ZoomX 17 shoes compared ASICS vs Nike — A-TPU (FF Leap) against PEBA (ZoomX). Is aliphatic TPU the new king of super-foams? The Metaspeed racers and Superblast vs Vomero Plus.
• ZoomX vs PWRRUN PB 20 shoes compared Nike vs Saucony — the closest cross-brand PEBA pairing in feel. Plus an honest look at where Saucony's lineup has gaps.

Decode the foam names

A foam badge — ZoomX, FuelCell, DNA, PWRRUN — names a brand and sometimes a process, but rarely the polymer, and the same badge can sit on genuinely different chemistries across one lineup. What running-shoe foam names actually mean decodes each badge into the foam actually under your foot, shoe by shoe; the companion essay Same name, different foam tells the story behind why.

How to read these pages

Each foam page covers four things: (1) the chemistry — what the polymer actually is and how the foam is processed; (2) the runner tradeoffs — weight, energy return, durability, ride feel; (3) a handful of featured shoes that are good representatives of the foam, each with a one-line case for picking it; and (4) the complete catalog appendix — every approved shoe in our database that uses that chemistry, linked.

A single shoe often appears on more than one page. Modern racers routinely stack a PEBA top layer over an EVA carrier, and a "supercritical" foam might be supercritical EVA, supercritical PEBA, or supercritical TPEE. Where that happens we list the shoe on every applicable page so the appendix really is exhaustive.