Cushioning Technologies 101

Feb 19, 2002
Pulled this from a 1998 Runners World... no Shox, but a good primer for anyone looking for running shoes (or anyone interested in cushioning tech.)

Inside cushioning technologies. (running shoes)(Evaluation) Relevancy: 100; ( Runner's World ) Carrozza, Paul; 09-01-1998 Size: 39K Reading Level: 11.
Every major running shoe company heralds its cushioning system as the reason why you should buy its shoes, but is it? When buying running shoes, you must remember you are buying the entire shoe and not just the cushioning technology. There are at least two other things you should consider ahead of these systems: the shoe's fit and the shoe' s midsole foam.

Fit is the most important determinant of how well a shoe will perform for you. If a shoe doesn't fit properly, none of its vaunted properties will matter. That's why we always emphasize that finding the best- fitting shoe is your job number one when buying new shoes.

The highly advertised cushioning systems make up just one part of a shoe's cushioning and "ride" properties. The larger part comes from the shoe's midsole foam. There are two basic midsole foams, EVA and polyurethane, which have quite different characteristics. When evaluating a shoe's cushioning, you should always consider the foam that surrounds the particular cushioning system.

EVA: EVA foams are softer, lighter and more flexible than polyurethane foams. Because EVA compresses more readily than polyurethane, EVA midsoles usually provide less stability than polyurethane and don' t last as long. EVA midsoles are often preferred by lighter runners (including many women) who want a smooth, soft, flexible ride from their running shoes.

Polyurethane: Polyurethane foams are denser, heavier and stiffer than EVA foams and provide more stability and durability than EVA. Polyurethane midsoles are often preferred by heavier runners who want a firmer, more stable ride and shoes that offer maximum durability.

When evaluating cushioning systems, there are three other things to take into account. First, since cushioning systems aren't foam- based, a cushioning system can make a midsole more durable by replacing some of the midsole foam. And the larger the cushioning system, the more foam it replaces.

Second, cushioning systems generally weigh more than foam, so they add to the shoe's overall weight. And third, the cushioning systems and foams must be "married" perfectly in the midsole. If they're not, the cushioning system can actually become a pressure point that makes the midsole feel as if it has a bump in it.

Below, we report on all the major cushioning systems. Each does what it's supposed to do: improve the midsole's shock-absorbing capacity. But there is no perfect system. Each has certain strengths and weaknesses. You'll want to consider these when you're trying on new shoes. At the same time, remember the first rule of shoe selection: let fit be your guide.

Adidas adiPRENE

What it is: High-density rubber pads placed under the rearfoot and forefoot.

What it does: Lessens impact.

Strengths: Creates smooth ride Absorbs shock

Weeakness: Pads are small

Asics Gel

What it is: Different types of pads made of silicone (or silicone- based) gel and placed in the midsole under the rearfoot and forefoot.

What it does: Disperses shock.

Strengths: Can't deflate Allows for smooth ride

Weakness: Pads are small and thin

Avia Cantilever

What it is: A concave outsole in the rearfoot that flares upon impact, forming a wide base to disperse shock.

What it does: Absorbs shock and creates a stable rearfoot by allowing the runner's heel to sink.

Strengths: Enhances cushioning Adds stability

Weakness: External cantilever can crack

Brooks HydroFlow

What it is: Pads filled with a silicone oil that flows within them.

What it does: Cushions the foot upon impact. HydroFlow ST (for stability) units in some shoes create a soft spot in the center of the rearfoot, which also stabilizes the foot.

Strengths: Lessens impact Increases durability HydroFlow ST pads add rearfoot stability

Weaknesses: Heavy ST pads' stability properties reduced by orthotics

Etonic Eon Air (formerly StableAir)

What it is: A nonpressurized air system using ambient (outside) air.

What it does: Reduces shock.

Strengths: Creates a cushiony spot in the rearfoot

Weakness: Pads aren't pressurized

Fila 2A

What it is: A pod (or system of pods) using ambient (outside) air with plastic pillars.

What it does: Absorbs shock and provides stability.

Strength: Creates crash pad for shock absorption

Weakness: 2A is very thick and has a different feel than the foam around it

Mizuno Wave

What it is: A highly resistant plastic sheet (roughly shaped like a wave) sandwiched between two layers of foam in the midsole.

What it does: Adds durability to the midsole and disperses shock.

Strengths: Disperses shock Doesn't interfere with ride Creates rearfoot stability

Weakness: Stiff

New Balance Abzorb

What it is: A layer of rubber that sits on top of the midsole in the rearfoot.

What it does: The Abzorb pad adds shock absorbency and durability to the midsole.

Strengths: Enhances shock absorption Increases durability

Weaknesses: Incorporates no new materials Heavy

Nike Air

What it is: The "air" is actually an inert gas contained within a mattresslike unit encapsulated in the midsole. Zoom Air, now used in several shoes, is thinner and more flexible than Nike's conventional air units.

What it does: Cushions the foot and, by displacing a considerable amount of midsole foam, adds durability.

Strengths: Weighs little Absorbs shock well

Weakness: Can deflate

Puma Cell

What it is: An insert of interlocking, honeycomb-shaped cells made from a polyurethane elastomer.

What it does: Cushions the foot, but mainly reduces use of foam to increase the life of the midsole.

Strengths: Makes the shoe more Durable Large units

Weaknesses: Lacks flexibility Needs heavy impact to compress fully

Reebok DMX

What it is: An air-cushioning transfer system that allows air to flow from the rearfoot to the forefoot (or midfoot, depending on the shoe) and back.

What it does: Cushions the foot upon impact and through gait cycle.

Strengths: Provides good cushioning Adds durability

Weaknesses: Lacks flexibility Heavy

Saucony GRID

What it is: A rearfoot cassette made of Hytrel strings that are strung like a tennis racquet to form a cradle for the foot.

What it does: Flexes and conforms to the shape of the heel as the rearfoot strikes, to cushion and support the foot.

Strengths: Creates a "sweet spot" in the rearfoot Adds cushioning without sacrificing stability

Weakness: GRID's strengths compromised by orthotics
Just to add what you got. Got it from

Basically a glossary of all proprietary technolgoies of different companies.

Construction & General Terminology
CM-EVA: Compression molded ethylene vinyl acetate foam.

Combination Lasted: The use of a fibrous stabilizing board, glued into the heel when the shoe is being constructed. The combination of the slip lasted forefoot (for flexibility) with the stabilizing board in the heel gives the shoe more stability and versatility.

High Frequency (HF) Welding: The use of superheated polymers molded to the vamp to add support and structure to the upper, replacing synthetic suede and synthetic leather overlays.

Injection Molded EVA (IM-EVA): Process whereby ethylene vinyl acetate foam is injected into molds to make it a bit more uniform and durable. Process is difficult to control as foam continues to expand after the injection.

Last: A three-dimensional model of a foot, around which the shoe is constructed.

Last Shapes: Variously shaped models used to accommodate different types of feet. Key difference is the height of the arch. Generally, the higher the arch, the more curved the last; the lower the arch, the straighter the last, though there is no defined parameter for the distinction between shapes.

Medial Post: Denser CM-EVA foam, polyurethane foam, TPU device, or some combination of these, used on the inside edge of the shoe to curb pronation.

Pebax: Formulation of nylon which has a low specific gravity and superior elasticity and durability than conventional nylon.

PU: Polyurethane foam.

Slip Last: Shoe construction method whereby the upper of the shoe is placed over the last and secured with stitches down the center of the foot bottom, then glued to the midsole.

Sockliner: The innersole of the shoe, which is usually removable.

Strobel slip last: Shoe construction method whereby the upper of the shoe is placed over the top of the last while a sole-shaped fabric board is placed below it. The two are stitched together around the perimeter of the sole. The board varies from thin flexible materials to thicker, more stable materials, or a combination of the two and is used to improve stability or flexibility.

TPU: Thermoplastic urethane used in devices to prevent overpronation.

Vamp: The portion of the shoe upper which wraps around the toe and extends back to the heel, excluding the tongue.

Shoe Manufacturers Terminology
3D Torsion: Device which causes the shoe to return to a stable base after allowing the foot to twist in its natural movement during the gait cycle. Differs from Torsion by extending upwards into the arch. (adidas)

a3: Stabilizing cushioning device which guides the foot during heel compression to offset overpronation. (adidas)

ABZORB: Visco-elastic (elastomer) polymer pads to absorb shock. (New Balance)

adiPRENE: Specially produced, compressed, injected EVA foam insert; also a visco-elastic polymer insert which performs the same function. (adidas)

adiPRENE +: Specially produced, compressed, injected EVA foam insert layer, or full forefoot formulation used for forefoot cushioning. (adidas)

Aeroflo: Midfoot ventilation system to allow the cooling of the foot on impact (Fila).

AHAR: ASICS High Abrasion Rubber. (ASICS)

Air: Pressurized air pads (some with varied air pressure) to absorb shock of impact. (Nike)

Air Cushion: Chamber which forces air as a cushion. (Merrell)

Air Flow CCB: Breathable torsional shank support. (Diadora)

Archtech: Midfoot shank device which causes the shoe to return to a stable base, after allowing the foot to twist in its natural movement during the gait cycle. (Puma)

BioLock: Integrated lace/strapping system to lock heel in place.

BRS 1000: Durable carbon rubber compound. (Nike)

C-CAP: Compression-molded ethylene vinyl acetate. (New Balance)

CELL: Hexagonal polyurethane cells of varying size with various amounts of CM-EVA or PU foam for support, with a slower rate of compression or breakdown than foam. (Puma)

DCS: Double Cantilever System; opposing cantilevers which provide cushioning and stability. (Avia)

DMX foam: PU foam insert, shaped like DMX bladders, to attenuate shock on impact. (Reebok)

Double Action 2: Visco-elastic (elastomer) polymer units which absorb shock, denser (red) unit in heel, more elastic (green) unit in forefoot. (Diadora)

Dryz: Copolymer foam moisture managing system in footbed. (Etonic)

DuoMax: Denser CM-EVA used for pronation control. (ASICS)

Duralon: Blown rubber for lightness, with a toughened skin for more durability. (Nike)

Dynamic Cradle: Separate contoured CM-EVA unit which guides the transitioning foot for proper toe-off. (ASICS)

Everdure: High abrasion rubber. (Etonic)

EverTrack: High abrasion rubber. (Puma)

EFR: Engineered Forefoot Ride; combination of blown rubber and carbon rubber allowing durability and lightness in a forefoot rubber.

FleXoft: Blown rubber formulation. (Diadora)

FOM: Low density foam pad for forefoot cushioning. (Avia)

GEL: Encapsulated, semi-solid silicon like substance. (ASICS)

GRID: Matrix of synthetic strands to absorb shock, like a tennis racquet absorbs and releases shock from a ball. (Saucony)

HPR: High Performance Rubber. (Brooks)

HydroFlow: Divided chamber filled with liquid silicon oil to flow from chamber to chamber under pressure of impact. (Brooks)

HydroMove (Lining): Polyester fiber that wicks moisture to the surface for evaporation. (Reebok)

ICO-10: Shock attenuating polymer pad. (Etonic)

IGS (Impact Guidance System): Integrated cushioning and stabilizing technologies engineered to improve the shoe's ride. (ASICS)

iCELL (Internal Cell): Hexagonal polyurethane cells of varying size, that break down or compress at slower rate than foam. (Puma)

ldCELL (Low Density Cell): Integrated co-molded foam, with a slow compression rate, which fits precisely into a forefoot cavity in the CM-EVA midsole. (Puma)

Integrated Support System: Combination midfoot shank support and anti-pronation device. (Saucony)

KMS 200: Specific recipe for EVA that results in predictable quality. (Puma)

Lightstrike EVA: Very fine quality ethylene vinyl acetate foam which is lighter and more durable than lesser forms. (adidas - though not proprietary)

Lite 2002: Low profile rubber sole for traction and grip. (Tecnica)

M-Chip: TPU or TPR (resin) inserts which allow for customization of cushioning or stability in the midsole. (Merrell)

Mizuno Intercool: Full-foot dynamic ventilation system that expels hot, humid air from the shoe. (Mizuno)

Ndurance: High abrasion rubber. (New Balance)

Ortholite innersole: Material which resists compression coupled with elastomer pads. (Teva)

PE Launch Pad: Polymer pad for shock absorption. (Bite)

Phylite:Lightweight midsole/outsole blend. (Nike)

Phylon: Lightweight CM-EVA. (Nike)

Podular: Articulated forefoot design that allows free forefoot movement and flexion. Often used as the suffix "Pod," e.g. HyperPod, MC-Pod, StablePod, CushPod and TerraPod. (Brooks)

Regrind: Outersole rubber which is recycled from previous running and athletic shoes. (Nike)

Roll Control: Dense EVA for medial stability. (The North Face)

Rollbar: Graphite device used to prevent overpronation. (New Balance)

Shox: Urethane pillars which compress between TPU plates to cushion the ride of the shoe (Nike).

SL-1: Semi-straight last that is snug from heel through forefoot to fit narrower foot types. (New Balance)

SL-2: Semi-straight last that is snug in the heel with a wider, taller toebox for wider feet and to allow for the curved shape of higher arched feet. (New Balance)

SpEVA: Special ethylene vinyl acetate foam with polymers in the micro cellular spaces to improve elasticity. (ASICS)

Spider Rubber: Patented super sticky rubber formulation. (Teva)

Stability Web: Device in midfoot which causes the shoe to return to a stable base after allowing the foot to twist in its natural movement during the gait cycle. (New Balance)

Stable Air: Air-filled pads which absorb and deflect the shock of impact. (Etonic)

T-GRID: Combination torsional device and GRID cushioning system in one TPU unit. (Saucony)

Techniplate: Ballistic nylon plate for protection of midsole/feet from trail debris. (Tecnica)

TNF Trail Grip: Rubber formulation for traction on trails. (The North Face)

TRB: Torsional rigidity bar. (Saucony)

Torsion: Device which causes the shoe to return to a stable base after allowing the foot to twist in its natural movement during the gait cycle. (adidas)

Trusstic System: Support device which forces the shoe to stabilize after the foot completes its natural twisting motion during the gait cycle. (ASICS)

Tuned Plate: Slotted, flexible polymer plate for protection and torsional stability on rough ground. (Salomon)

Twist Gel: A ratchet wheel-shaped silicon pad which cushions in every plane of the toe-off phase. (ASICS)

Two-Tier Lacing: Offset rows of eyelets to cinch the foot securely in the shoe. (The North Face)

Waffle Grip: Hollow, hard rubber waffle studs filled with soft rubber for grip. (Nike)

Wave: Sabilizing and cushioning plate sandwitched between EVA layers which resembles corrugated cardboard or roofing. The different configurations include parallel waves (cushioning), asymmetrical waves (stability) and double waves (motion control). All have stabilizing fins which act as a shank support. (Mizuno)

X-2 :D
ense foam material inserted into the midfoot cavity increasing stability and durability of trail shoes. (North Face).

XT 600: High durability rubber. (Saucony)

XT 900: High durability rubber. (Saucony)

VS-1: Elastomeric polymer pads to absorb shock (Mizuno)

3A: Visco-elastic (elastomer) polymer units which absorb shock. (Fila)

3D Ultralite: Injection molded mixture of rubber and EVA which eliminates the need for separate midsole/outsole pieces. (Reebok)
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