Carbon Plate
Also: carbon fibre plate, carbon fiber insert
A rigid structural element embedded within the midsole of an elite racing shoe, made from carbon fibre composite. Contrary to popular belief, the carbon plate does not act as a spring — carbon fibre does not compress or stretch. Its two functions are biomechanical: it acts as a stabiliser that prevents the ultra-soft PEBA foam from compressing irregularly, and as a lever that stiffens the metatarsophalangeal (MTP) joint during toe-off, reducing the mechanical work required from the calf and Achilles tendon. Different brands implement the plate differently — a single spoon-shaped plate (Nike), multiple rods (Adidas), or an extended plate that protrudes past the toe (Puma).
In context
The Nike Vaporfly 4 uses a unified Carbon Flyplate while the Adidas Adios Pro 4 uses Energy Rods 2.0 — individual carbon-infused rods that create a rolling transition rather than a single snap point.
Carbon Flyplate
Nike-specific term
Nike's proprietary name for the unified, spoon-shaped carbon plate used in the Vaporfly and Alphafly range. The Flyplate's single-piece geometry creates a concentrated flex and snap point at the forefoot, producing the aggressive, mechanical "pop" that Nike shoes are known for. The Alphafly 3 uses a dual Flyplate configuration for additional propulsion force.
Drop
Also: heel-to-toe drop, heel drop, offset
The difference in stack height between the heel and the forefoot of a shoe, measured in millimetres. A shoe with 40mm of heel stack and 32mm of forefoot stack has an 8mm drop. Higher drop (8mm+) is more forgiving on the Achilles tendon and calf and suits heel strikers and runners transitioning from traditional trainers. Lower drop (4-6mm) demands more from the posterior chain but suits forefoot strikers with established mechanics. Most elite racing shoes in 2026 sit at 5mm to 8mm drop.
In context
The New Balance FuelCell SC Elite v5 doubled its drop from 4mm (v4) to 8mm (v5), significantly broadening its appeal to heel strikers and runners with Achilles sensitivity.
Energy Rods
Also: Energy Rods 2.0 — Adidas-specific term
Adidas's proprietary propulsion system used in the Adizero Adios Pro range. Rather than a single unified plate, Energy Rods are multiple carbon-infused rods positioned to mirror the metatarsal bones in the foot. The rods work with the shoe's forefoot rocker to create a smooth, wave-like rolling transition rather than a single concentrated snap point. Energy Rods 2.0, introduced in the Adios Pro 4, are stiffer and more precisely placed than the original version. See our Adios Pro 4 vs Vaporfly 4 comparison for how this chassis scores in R.A.C.E.
ENERGYRIM
Adidas-specific — Adizero Adios Pro Evo 3 (2026)
A perimeter carbon frame used on the limited Adizero Adios Pro Evo 3 instead of a traditional full-length underfoot plate. Carbon runs along the outer edge of the midsole while the centre forefoot relies on Lightstrike Pro Evo foam for compliance. Adidas positions it as stability at the rim and cushioning where the foot loads most — with less mass than a solid plate spanning the shoe. It debuted on the London 2026 marathon podium; Racing Shoe Guide covers the race context in our London 2026 report. This is a distinct chassis from Energy Rods 2.0 on the Adios Pro 4.
In context
ENERGYRIM is why the Evo 3 can chase ~97g in race sizes while staying near 39mm stack — mass moves out of a full plate and into a rim plus ultra-light upper. We have not scored the Evo 3 under R.A.C.E. yet; the Adios Pro 4 remains our scored Adidas marathon pick at 9.4/10.
EVA Foam
Also: ethylene-vinyl acetate
The traditional midsole foam used in running shoes before the super shoe era. EVA absorbs impact energy but returns only 60 to 65% of it per stride — the remainder is lost as heat. It is significantly denser and heavier than modern PEBA foam. Most daily training shoes still use EVA or EVA-blend compounds. The shift to PEBA foam in elite racers is the primary reason super shoes improve running economy.
Forefoot Rocker
Also: toe spring, rocker geometry, rocker sole
The curved upturn at the toe of a carbon plate shoe's midsole. Because the carbon plate prevents natural toe flexion, a flat shoe would cause the foot to slap the ground with every stride. The rocker geometry solves this by allowing the foot to roll forward smoothly through the stride cycle — the plate and curved foam act together like a wheel. More aggressive rocker geometry produces a faster transition but less ground feel. Rocker geometry is one of the key variables that determines how different a super shoe feels from a traditional racing flat.
In context
The Puma Fast-R Nitro Elite 3's highly rockered geometry is what gives it the sensation of being pulled forward through each stride — the shoe actively initiates the transition rather than waiting for the runner to push off.
Heel Striker
Also: rearfoot striker, heel-toe runner
A runner whose foot makes initial contact with the ground at the heel rather than the midfoot or forefoot. Heel striking is the most common gait pattern among recreational runners. Most elite carbon plate shoes are optimised for midfoot or forefoot striking — their forefoot rockers and plate geometries assume that the propulsion cycle begins through the forefoot. Heel strikers require shoes with higher drops, wider heel platforms, and more protective heel geometry to get the benefit of a super shoe without instability or injury risk. See our guide to carbon plate shoes for heel strikers.
MTP Joint
Also: metatarsophalangeal joint, toe joint
The metatarsophalangeal joint is where the long bones of the foot (metatarsals) meet the toe bones (phalanges) — the knuckle-like joint at the base of each toe. During a normal running gait, this joint must flex significantly at toe-off, requiring substantial work from the calf muscles and Achilles tendon. The carbon plate's primary biomechanical function is to stiffen this joint, reducing that muscular work. By stiffening the MTP joint across thousands of strides in a marathon, the carbon plate produces a meaningful cumulative reduction in calf fatigue — which is the real source of super shoe performance gains.
PEBA
Also: polyether block amide, super foam, aerospace foam
Polyether block amide is the polymer compound family used in the midsoles of virtually all elite racing shoes. PEBA foams return 85 to 90% of kinetic energy per stride — compared to 60 to 65% for traditional EVA foam. They are significantly lighter and softer than EVA while being more resilient under compression. Different brands market their PEBA-family foams under proprietary names: Nike ZoomX, Adidas Lightstrike Pro, ASICS FF Leap / FF Turbo+, Brooks DNA Gold, and New Balance FuelCell are all PEBA variants. Puma's Nitro Elite A-TPU uses a related but distinct aliphatic TPU compound rather than PEBA.
In context
PEBA foam is the primary reason super shoes improve running economy. The carbon plate's role is largely to stabilise and control the extremely soft PEBA material — without it, a 40mm stack of pure PEBA would be dangerously unstable.
PWRPLATE
Puma-specific term
Puma's name for the carbon plate system used in the Fast-R Nitro Elite range. The PWRPLATE in the Fast-R 3 is notable for extending visibly past the end of the upper — beyond the toe — creating a longer lever arm than any competitor. This extended geometry amplifies the toe-off force more aggressively than a plate that terminates at the toe box.
R.A.C.E. Score
Racing Shoe Guide proprietary methodology
The R.A.C.E. Score is Racing Shoe Guide's proprietary 10-point rating system for evaluating carbon plate racing shoes. The four components are: Return (35%) — energy return, foam resilience, and carbon plate propulsion efficiency; Anatomy (25%) — upper fit, heel lockdown, breathability, and toe box width; Chassis (25%) — plate geometry, rocker design, stack height, and drop suitability; Economy (15%) — weight-to-cushion ratio, durability, and price-to-performance value. See our full R.A.C.E. methodology page for complete scoring criteria.
Running Economy
Also: metabolic cost of running, oxygen cost
Running economy is the measure of how much oxygen (and therefore metabolic energy) your body consumes to maintain a given running pace. A runner with better running economy uses less energy at the same speed — which means they can sustain that speed for longer before exhaustion. Super shoes improve running economy by 3 to 4% through the combination of PEBA foam energy return, carbon plate MTP joint stiffening, and rocker geometry. This typically translates to 2 to 3 minutes saved over a full marathon. Running economy is why super shoes make you faster without improving your fitness — they reduce the energy cost of the fitness you already have.
SpeedVault+
Brooks-specific term
Brooks' name for the size-customized carbon plate system used in the Hyperion Elite 5. Unlike most competitors whose plates are scaled from a single mold across sizes, SpeedVault+ plates are individually engineered per shoe size — the geometry is tuned to the biomechanical leverage requirements of each foot length. This produces a more precisely calibrated snap and flex point across the size range.
Stack Height
Also: midsole stack, cushion height
The total thickness of material between the bottom of the foot and the ground, measured in millimetres at the heel. Stack height determines how much foam is available for energy return — more stack means more PEBA material compressing and rebounding with each stride. World Athletics caps stack height at 40mm for sanctioned competition (including all major marathons). Most elite shoes sit between 35mm (Nike Vaporfly 4) and 40mm (Nike Alphafly 3, Puma Fast-R 3, ASICS Metaspeed Sky Tokyo). Higher stack height increases energy return but also increases instability, which is why the carbon plate is necessary to control it.
In context
The ASICS Metaspeed Sky Tokyo sits at 39.5mm — 0.5mm under the World Athletics legal limit — extracting the maximum available cushioning within the rules.
Super Shoe
Also: carbon plate shoe, elite racer, super trainer (misnomer)
An informal term for modern elite racing shoes that combine PEBA-family foam, a carbon or carbon-composite plate, and rocker geometry. The term emerged around 2017 with Nike's original Vaporfly 4% and became widespread after the shoe's documented impact on marathon world records. Not all carbon plate shoes are super shoes in the performance sense — some training shoes use carbon plates for guidance rather than propulsion, without the PEBA foam stack that drives the performance gains. When Racing Shoe Guide uses the term, it refers specifically to shoes meeting all three criteria: PEBA foam, carbon plate, and rocker geometry.
Toe Spring
The angle at which the toe of a shoe curves upward from the ground when placed on a flat surface. All shoes have some degree of toe spring, but super shoes have dramatically more — often 15 to 30 degrees of upturn. Toe spring is the visible expression of the forefoot rocker geometry. A higher toe spring initiates the rolling transition earlier in the gait cycle and produces a faster forward propulsion, but reduces ground feel and can feel unnatural at easy paces.
World Athletics 40mm Rule
Also: stack height limit, shoe regulations
World Athletics — the global governing body for track and road running — limits the stack height of competition shoes to 40mm for sanctioned events. This applies to all World Athletics-labelled road races, including all six Abbott World Marathon Majors. Shoes exceeding 40mm cannot be worn in official competition. The rule was introduced in 2020 specifically in response to the performance advantage of PEBA foam super shoes. The Adidas Adizero Prime X 2 (50mm stack) is a notable example of a commercially available shoe that exceeds the limit and is not competition-legal. All shoes in the Racing Shoe Guide top 12 rankings comply with the 40mm rule.
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Open the Comparison Tool →Common glossary questions
What does PEBA stand for in running shoes?
PEBA stands for polyether block amide — the polymer family behind most elite midsole foams. It returns roughly 85–90% of stride energy vs 60–65% for traditional EVA. Nike markets it as ZoomX, Adidas as Lightstrike Pro, ASICS as FF Leap / FF Turbo+, Brooks as DNA Gold, and New Balance as FuelCell.
Does the carbon plate act as a spring?
No. Carbon fibre does not compress like a spring. The plate stabilises soft PEBA foam and stiffens the MTP joint at toe-off, reducing calf and Achilles work. Most of the measured running-economy gain comes from the foam, not the plate — a distinction we use in the Return pillar of R.A.C.E.
What is stack height, and why does 40mm matter?
Stack height is midsole thickness at the heel, in millimetres. More stack usually means more foam and more return — but also more instability without a plate. World Athletics caps competition stack at 40mm; every shoe in our 2026 rankings hub complies for marathon legality.
What is heel-to-toe drop?
Drop is heel stack minus forefoot stack. Higher drop (8mm+) is easier on the Achilles and suits heel strikers; lower drop (4–6mm) suits forefoot loaders. Chassis scores on this site weight drop suitability alongside rocker geometry — see our heel-striker guide for models that forgive rearfoot landing.
What is the World Athletics 40mm rule?
World Athletics limits competition shoe stack to 40mm on the road. It applies to Abbott World Marathon Majors and other sanctioned events. Shoes above the cap (for example some training-only builds) cannot be worn in official competition even if they are sold at retail.