Cutting the carbon plate out of Nike Vaporfly shoes by 66–72% changed running economy by exactly 0.55%. That’s not significant. The plate isn’t what’s making you faster.
A 2026 study in the Scandinavian Journal of Medicine & Science in Sports tested a different idea: what if you void the midsole — hollow it out — so the foam can compress deeper on each footstrike? For forefoot and midfoot strikers specifically, that geometry change delivered a 2.9% economy improvement. No extra stack height. No thicker shoe. Just a smarter shape.
If you run on your forefoot or midfoot, this matters. Most super-shoe research used rearfoot strikers. You may not be one of them.
What’s Actually Driving Running Economy in Carbon Plate Shoes
The short version: the foam does the work. The plate helps channel it. The geometry may matter most of all.
Running economy (RE) is how much oxygen you burn to cover a given distance at a given pace. Lower oxygen cost equals faster racing at the same effort. A 2–3% RE improvement sounds small. At marathon pace, it can mean 4–6 minutes.
Here’s the breakdown by technology component:
The foam contributes around 1.8% on its own. That’s PEBA (polyether block amide) foam — used in Nike’s ZoomX and Adidas’s LightStrike Pro — which returns roughly 85% of compression energy vs 50–60% for standard EVA. Think of it like a trampoline vs a yoga mat. Same force in, very different energy back out.
The plate’s bending stiffness? Mostly irrelevant in isolation. Healey and Hoogkamer cut Vaporfly plates to near-uselessness and measured no meaningful economy change. The plate’s job is to stiffen the metatarsophalangeal (MTP) joint and redirect energy — it works in combination with the foam, not alone.
How Hollow-Midsole Geometry Changes the Game for Forefoot Strikers
Here’s the mechanism. A forefoot striker lands on the ball of their foot. That means the midsole under the forefoot takes the brunt of each stride. If the foam there is dense and solid, compression is limited. Energy return is limited.
Void it. Create a hollow structure underneath the foam layer. Now the foam can compress 2.35 cm on impact instead of 1.69 cm. That extra compression stores more energy — 15.64 joules per stride vs 11.03 joules in a solid midsole. And it returns more: 14.00 joules back vs 9.87 joules.
In short: a hollowed-out midsole lets the foam act like a deeper spring. More in, more back out.
That energy storage difference translated to a 2.9% economy improvement at race pace. For a runner averaging 4:58/km (3:30 marathon), 2.9% is roughly 6 minutes off a full marathon.
There’s a wrinkle about strike pattern and which shoe research applies to you. Elite runners are ~81% midfoot or forefoot strikers. Recreational runners run ~89% rearfoot. Most lab testing uses rearfoot strikers. So a lot of the “super shoe research” in your feed was done on a population that doesn’t match the fast end of the amateur field. If you’re a competitive forefoot or midfoot striker, the hollow-geometry data speaks directly to you.
Carbon Plate Shoe Geometry Matters — Curved vs Flat
Not all carbon plates are the same shape. A 2024 analysis in Scientific Reports compared curved (rocker) plates to flat plates and found a 3.26-percentage-point gap in economy improvement: curved plates delivered 3.45% vs 0.19% for flat plates.
The curved plate also reduced peak forefoot plantar pressure by 5.51–12.62 percentage points more than flat plates. For a forefoot striker who already loads the ball of their foot hard, that pressure reduction matters over 42 km.
Check your shoe. A rocker sole profile isn’t just aesthetics.
Responders and Non-Responders
About 1 in 4 runners gets nothing from super shoes. Some get slightly worse economy.
| Population | Responder rate | Economy gain (responders) |
|---|---|---|
| Recreational runners (various studies) | 69–81% | Varies |
| Mixed runners, plate stiffness study | ~56% | ~2.9% |
| Elite runners in Vaporfly | Range wide | Up to +11.4% or −11.3% |
| Non-rearfoot strikers, hollow midsole | Majority significant | 2.9% (mass-corrected) |
The mechanism behind non-response involves ankle kinematics. Responders reduce ankle energy requirements when the plate stiffens the MTP joint. Non-responders increase ankle plantarflexion instead — working harder, not less. It’s not about fitness level. It’s about how your individual ankle-MTP system coordinates.
You can’t tell which group you’re in from a shoe review. You need your own data.
One Athlete’s Economy Data Tells the Story
Take a runner named Tom, 34 years old, training for a sub-2:50 marathon on 55 miles per week. He’s a committed midfoot striker with a 185 cadence and a consistent forefoot loading pattern. He bought a high-stack carbon shoe based on good reviews and wore it for 10 long runs.
His drift ratio — the HR/pace coupling that measures aerobic efficiency — showed no improvement compared to his previous trainer. Same sessions, same HR, same pace. He was in the non-responder bracket for that shoe’s plate geometry.
He switched to a shoe with a hollowed midsole and curved plate. Eight weeks later, his long run efficiency had improved 2.4%. His marathon came in at 2:48. The shoe wasn’t the only variable. But the data made it visible.
AthleteOS tracks this automatically. Every shoe you log creates its own efficiency factor trend — the drift ratio across workouts in that shoe. If a model isn’t working for you, you’ll see it in four to six sessions, not after wasting a race.
The 40mm Rule and What It Actually Means
World Athletics capped road racing shoe stack height at 40mm in 2020. One plate maximum. Shoes must be available at retail for at least 4 months before competition.
The number sounds limiting. It’s not the ceiling it appears to be. Research shows that going from 40mm to 50mm adds only about 0.6% more economy — a real but small increment. The hollow-geometry finding matters precisely because it extracts more performance from within the current 40mm limit, not beyond it.
Your PEBA foam has a shelf life too. After 450km, economy drops roughly 2.28% — nearly erasing the super-shoe economy advantage you paid for. If you’re logging shoe mileage with AthleteOS, you’ll see your foam degradation curve before race day.
Stack height isn’t the only lever. Geometry is legal, accessible, and — for forefoot strikers — possibly the bigger one.
Are You Getting the Economy You Paid For?
Don’t assume the shoe is working. Three things determine whether it is: your strike pattern, your ankle-MTP kinematics, and your shoe’s mileage.
You can’t test the middle one without a lab. But you can track the first and third with every workout.
AthleteOS logs your shoe per session and computes a per-shoe running economy delta using HR/pace coupling — the same efficiency factor signal used in aerobic decoupling analysis. For forefoot and midfoot strikers, this turns the abstract responder/non-responder literature into a concrete answer: does this shoe improve your efficiency number or not?
If it doesn’t, you’re not in the 19–44% non-responder bracket through bad luck. You’re in it with data, which means you can act on it.
The foam expires. The data doesn’t.