Why foam chemistry matters more than ever for trail running shoes

Today’s trail shoes are expected to do more than ever: scale mountains, sprint fire roads, endure across seasons, and leave a lighter footprint behind. The material at the heart of all that? Foam. But not all foams are created equal. While EVA, TPU and PEBA have powered past generations of super shoes, each comes with a trade-off, and in many cases, a ticking clock.

That’s the challenge the team behind the norda™ 005 set out to solve. Working in partnership with Envalior, norda engineered the world's lightest and most resilient trail shoe using a 100% Arnitel® Performance foam midsole – delivering rebound, durability, and climate adaptability unlike anything else on the market.

Arnitel® Performance, a thermoplastic elastomer, is changing the equation. It’s not only engineered for rebound, resilience, and recyclability – it also enables high-performance design freedom, allowing brands like norda to reduce weight without sacrificing protection or propulsion. That balance is what sets the norda™ 005 apart in a crowded field of trail running shoes. Engineered for rebound, resilience, and recyclability, it’s built for the next generation of performance – not the last.

The cost of compromise

Every foam tells a story. The EVA story is one of affordability, but at the cost of consistency. It’s light and low-cost, however it demonstrates poor energy return and requires a chemical crosslinking step that makes it a bad option in terms of sustainability. TPU brings better energy return, yet suffers from performance drift in hot and cold temperatures, and also has environmental concerns. PEBA (TPE-A) is celebrated for its super-shoe bounce, but it often comes with a fragile feel when scaled for trail durability.

For trail runners and ultramarathoners, these limitations show up fast. One norda 005 tester said it best: “Most race shoes are done by 150 miles. I’m 300 in and still rolling. That says it all.” When you’re pushing through heat, snow, mud, and vertical gain, performance with caveats isn’t good enough.

Rethinking foam, from the chemistry up

Arnitel® Performance takes a fundamentally different approach. As a recyclable thermoplastic without chemical crosslinking, it offers advantages EVA and TPU can’t match. No nitrogen-based bonds means no NOx emissions during burn-off. No thermoset structure means it can be reprocessed for circular economy applications. And because it shares chemistry with grades certified for food contact, drinking water and medical use, it meets a higher bar of purity and process control.

Its ECO variants go even further – incorporating up to 50% renewable content (for example, rapeseed oil) and offering ISCC-certified biomass-balanced options that drop into existing production setups without extra tooling or reformulation. That’s performance with a conscience – and an infrastructure to scale.

Advanced foaming, smarter stability

In testing, Arnitel® Performance consistently delivers over 80% rebound, 15–20% higher than TPU, and up to 5% higher than PEBA in lightweight builds. It also retains that rebound over time and temperature. Unlike TPU, which can stiffen in cold and soften in heat, Arnitel® Performance keeps its modulus steady from –20°C to +100°C. That translates into fewer surprises underfoot, whether you're climbing an icy ridge or descending in desert heat.

Arnitel’s physical foaming process enables precise tuning, allowing designers to optimize rebound and stability without relying on thick stacks or carbon plates. One norda athlete put it simply, “The rebound just keeps giving – mile after mile. You feel it when the fatigue sets in, and it’s still springing you forward.”

One shoe to rule all terrain

Versatility isn’t just a bonus for trail runners – it’s essential. In a world where split surfaces are the norm, shoes need to transition seamlessly from technical trail to pavement to softpack and back again. Arnitel® Performance foams, such as the one used in the norda™ 005, give runners a stable, propulsive platform on any surface. That means no pit stops, no gear swaps, no unnecessary weight. Arnitel makes all-terrain readiness not just possible, but practical.

As one norda athlete shared: “I used to change shoes between road and trail. Now I just don’t.”

Arnitel® Performance isn’t just another foam. It’s the core of trail-ready innovation already powering elite gear like the norda™ 005. It’s the foundation for a new generation of trail shoes, where performance, sustainability, and real-world versatility converge. If you’re selecting materials for super shoes that have to go the distance – and come back ready for more – Arnitel ® Performance delivers.

Learn more about Arnitel® Performance

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