Running Shoe Specs Explained

Shoe listings are full of numbers that sound precise and are rarely explained. This is what each one means, and — more usefully — what range it actually falls in, measured across the 285 fully-specced shoes in the ATHLO+ Shoe Lab.

Heel-to-toe drop

The difference in foam thickness between the heel and the forefoot. A 10 mm drop means the heel sits 10 mm higher. It changes where load is distributed, not how much of it there is — a higher drop shifts work away from the calf and Achilles and towards the knee, roughly speaking, and a lower drop does the reverse.

In this dataset drop runs from 0 mm to 12 mm. 9 shoes are zero-drop and 48 sit below 6 mm, so the "low drop" end is a real minority — 8 mm is the median. There is no correct number, and switching abruptly between very different drops is the thing worth avoiding rather than any particular value.

Stack height

How much foam is underfoot, quoted at the heel and the forefoot. Heel stack here runs from 18 mm to 55.5 mm — the tallest being the Nike Vomero Premium at 55.5 mm.

One rule worth knowing: World Athletics caps stack height at 40 mm for road racing. A shoe above that is not race-legal for a ranked road result, which is why the very tallest shoes are marketed as trainers.

Plates

A plate is a stiff insert in the midsole. It does not generate energy; it stiffens the shoe so that a thick, soft foam can be used without the whole thing collapsing sideways, and it resists the toe joint bending as much as it otherwise would.

Of these 285 shoes, 73 use carbon and 177 have no plate at all — the rest use nylon, Pebax, rods or a proprietary variant, which are progressively more flexible. A plate is not an upgrade; it is a different tool, and a stiff racing plate under easy mileage is not doing you any favours.

Foam

The midsole compound, and the place brands compete hardest on naming. The names are marketing; the chemistry is not. Broadly, PEBA-based foams are lighter and return more energy than EVA-based ones, and supercritical foams (nitrogen-injected) sit between them. The lightest shoe in the Lab, the Nike ZoomX Streakfly 2 at 128 g, is a good illustration of what modern foam plus minimal upper gets you.

Weight

The most obvious figure and the most over-weighted one. It is quoted at a single sample size, usually a men's US9, so your pair will differ. A 30 g difference is noticeable; a 10 g difference is mostly a spec-sheet argument.

Compare by category

• Carbon plate racing shoes
• Super trainers
• Daily trainers
• Max cushion shoes
• Stability shoes
• Trail shoes

Compare by brand

• Hoka — 31 models
• Asics — 30 models
• Nike — 27 models
• Saucony — 24 models
• Brooks — 23 models
• Adidas — 22 models
• On — 22 models
• New Balance — 21 models
• Puma — 15 models

Or put any two to four shoes side by side in the ATHLO+ Shoe Lab.

Where these numbers come from

Manufacturer-published specifications compiled in the ATHLO+ Shoe Lab, powered by iRUN Singapore. These are specs, not our own test results, and nothing here is ranked or recommended. Figures are quoted at the maker's sample size and vary with yours.