GOT SOLE? THE DNA OF THE MID­SOLE

Un­der­stand­ing the Most Im­por­tant Tech­nol­ogy in Run­ning: Cush­ion­ing

Canadian Running - - GEAR - By Mary­lene Vester­gom

Ev­ery day, run­ning shoe man­u­fac­tur­ers are look­ing for the next in­no­va­tion. When it comes to pro­pri­etary tech­nol­ogy, foams have been a driv­ing force in this race, and the mid­sole is the an­chor, where the cush­ion­ing layer of foam re­sides un­der the in­sole and above the out­sole of run­ning shoes. Con­sider the new kids on the block – Boost, EverRun, FlyteFoam, Fresh Foam and ZoomX, to name just a few. These new for­mu­la­tions were cre­ated to not only ab­sorb shock but also to pro­vide sup­port and ex­tend the com­fort of the over­all ride. So how have mid­soles changed? For the run­ner, it’s about hav­ing a shoe that will move with your foot.

Foam 101

To­day’s mid­soles are the re­sult of an evo­lu­tion of foams. There are many poly­mers that can be thrown into the mix – let’s start with the ba­sics. EVA, which stands for ethyl vinyl ac­etate, is a type of copoly­mer foam that’s been used in the footwear in­dus­try for well over 40 years. When evas were first in­tro­duced, they were much less durable and less en­ergy ef­fi­cient than the com­pounds used to­day. “Over the last few decades, shoe man­u­fac­tur­ers have ex­per­i­mented by adding dif­fer­ent poly­mers,” says Brice New­ton, who works in Brooks’ global footwear di­vi­sion. Spencer White, V.P. of Sau­cony’s Hu­man Per­for­mance and In­no­va­tion Lab in Lex­ing­ton, Mass., ex­plains, “The big­gest im­prove­ments made to the foam com­po­si­tion also made the shoe lighter, bouncier and more abra­sion re­sis­tant, so they don’t need to use as much rub­ber on the bot­tom of the shoes, which again makes for a lighter-weight shoe.”

Now for as long as there have been evas, there have also been polyurethane (PU) foams. These are much more durable than evas but also much heav­ier with al­most the same amount of bounci­ness or en­ergy ef­fi­ciency. As an ex­am­ple, some PU foams, like mem­ory foams, of which some mat­tresses are made, have very poor en­ergy ef­fi­ciency. This means when you push on them, they re­tain that shape. “That’s not good for a run­ning shoe be­cause you want the shoe to re­cover and be ready for your next step,” says White. “It would be best if it could re­cover just as your foot is lift­ing off the ground to give you a lit­tle of that en­ergy back that you put into it.”

There are other draw­backs to the poured PU foams. Since they are open cell foams, they ab­sorb wa­ter and break down very easily. eva is a closed cell foam and is more durable but not as bouncy as shoe man­u­fac­tur­ers would like.

To a run­ner, a durable shoe is im­por­tant be­cause it main­tains its abil­ity to pro­tect the run­ner bet­ter. Be­cause eva breaks down steadily, af­ter you put in a few hun­dred kilo­me­tres in the shoe, you’re not get­ting the same kind of cush­ion­ing as you did dur­ing that first run.

EVA mid­soles also change over the course of a sin­gle run. Be­cause these foams are not 100 per cent en­ergy ef­fi­cient, with ev­ery step, you’re leav­ing a lit­tle en­ergy in the mid­sole. Ev­ery time you land, some of that en­ergy stays in­side the cen­tre of the foam and grad­u­ally over time heats up. White says that if you took a tem­per­a­ture probe and stuck it in the cen­tre of the heel of a run­ning shoe and then go for a run on a 21 C day, af­ter less than 5k, the tem­per­a­ture in the cen­tre of that heel could be over 50 C. eva gets sig­nif­i­cantly softer when it heats up, mean­ing that over the course of a run, the mid­sole gets softer and less able to ab­sorb the im­pact com­pared to the be­gin­ning of the run. Of course, when run­ners get fa­tigued at the end of the run they need cush­ion­ing. So it’s good to have a shoe that can still do it for you.

En­ter a new class of foams called Poly­mer Bead foams, specif ic a l ly Ex­panded Ther­mo­plas­tic Urethane (etpu).

“We’ve been look­ing for a long time for foams that can over­come some of these ear­lier prob­lems, and we ran across a new class of foams called Poly­mer Bead foams, and that’s what this ex­panded tpu foam is,” points out White. “What’s dif­fer­ent about everun is the base poly­mer and the man­u­fac­tur­ing process we’re us­ing. But what’s in­ter­est­ing is that these ex­panded tpu foams are much bouncier, much live­lier, more f lex­i­ble than eva ma­te­ri­als and much more durable and less tem­per­a­ture sen­si­tive.

“So everun is an etpu foam that main­tains its cush­ion­ing prop­er­ties about three times longer than eva. So it’s still break­ing down over time but much less dra­mat­i­cally. And be­cause it’s so en­ergy ef­fi­cient and not very tem­per­a­ture sen­si­tive, it main­tains its abil­ity to pro­tect run­ners at the end of their run bet­ter than eva,” says White.

New Bal­ance Fresh Foam Hexagons and 3D print­ing

The com­po­si­tion of the foam isn’t as im­por­tant as how the foam is be­ing shaped us­ing 3d print­ing, which you can check along the sides of the shoe. In the case of the Fresh Foam, hexagon shapes will ei­ther be con­cave go­ing in a pocket or con­vex stick­ing out and, de­pend­ing if it’s a run­ning shoe, train­ing shoe or trail shoe, the hexagons will have a dif­fer­ent con­fig­u­ra­tion. “In the most gen­eral sense, the lat­eral sides of a Fresh Foam side wall will be con­cave, says David Korell, footwear mer­chan­diser for New Bal­ance Canada. “So if a run­ner lands lat­er­ally on the heel or supinates, the foam is go­ing to com­press more into that con­cave pocket. And as the foot nat­u­rally pronates, that con­vex pocket is in­tended to be a bit firmer when it’s loaded with weight. So we can tune the mid­sole with­out hav­ing to add plas­tics or gels to do dif­fer­ent things heel-to-toe, just based on the shape of the hexagons.”

The long-term goal is for a con­sumer to stand on a scan­ning de­vice that would send in­for­ma­tion about their foot to a 3d printer so that a shoe could be cre­ated specif­i­cally for their in­di­vid­ual me­chan­ics. Last year, 44 pairs of 3d-printed Fresh Foam shoes were pro­duced and sold com­mer­cially for a lim­ited time for us$ 400 each as a test project.

Brooks BioMoGo DNA

“We’re us­ing what we call BioMoGo dna; it’s unique and pro­pri­etary to Brooks, and we’ve also re­cently launched Su­per dna. Both are dif­fer­ent forms of eva,” says New­ton. “For the BioMoGo, we’ve used an ad­di­tive in the eva that al­lows it to break down, which makes it com­pletely biodegrad­able, un­like other evas. The sec­ond part is the adapt­abil­ity of our evas. Brooks dna uses a non-New­to­nian f luid that has a con­sis­tency t hat is tot ally de­pen­dent on the stress ap­plied. So no mat­ter your weight, how you run or where you land, that mid­sole ma­te­rial will adapt to what­ever load you ap­ply to it.”

Nike ZoomX

Think­ing of break­ing the two-hour marathon? Well, that’s what Nike is hop­ing its new Nike Zoom Va­porf ly Elite with the new ZoomX mid­sole will do. And al­though you might not be ready to break this bar­rier, Nike has in­cluded this ZoomX mid­sole in the Nike Zoom Va­porf ly 4%.

Nike de­scribes the ZoomX mid­sole as a sys­tem that pro­vides re­spon­sive cush­ion­ing that al­lows the run­ner to max­i­mize on speed and ben­e­fit from a greater re­turn of en­ergy, with­out in­creas­ing de­mand on the calf. “The ground­break­ing new Nike ZoomX mid­sole and curved car­bon fi­bre plate work to­gether to pro­vide re­spon­sive cush­ion­ing and min­i­mized en­ergy loss at toe off,” says Tony Bignell, VP of footwear in­no­va­tion. Now the Va­porf ly 4% may not have all the in­no­va­tive bells and whis­tles of the Va­porf ly Elite, which is cus­tom de­signed for only their elite marathon­ers. How­ever, Nike says the per­for­mance-driven de­sign of this run­ning shoe makes it 4 per cent more ef­fi­cient than its pre­vi­ous fastest marathon shoe. And when it comes to the de­sign es­thet­ics, Nike has taken the idea of look­ing fast to a whole new level. The strik­ing aero­dy­namic heel counter, along with the Fly­mesh up­per with its mid­foot wrap, seem to make the foot and shoe f it seam­lessly to­get her as one unit .

Asics FlyteFoam

Asics uses many dif­fer­ent foams, de­pend­ing on the run­ner’s need, price point and even the pro­duc­tion process. “If the fo­cus is to cre­ate some­thing light­weight or with more bounce, then we would look for a spe­cific kind of foam that would de­liver these fea­tures,” says Asics’s Jork Ger­aets, global prod­uct line man­ager. “One of our foams is called Speva, and it has re­ally great bounce and a com­fort­able feel, per­fect for the recre­ational run­ner but it’s not the light­est weight. So it wouldn’t be the foam

we would use if we are cre­at­ing a fast shoe for a sub- three-hour marathon.”

Asics’s an­swer to t his is FlyteFoam. Ger­aets ex­plains that if you want to make the stan­dard mid­sole foam lighter, you would blow up the cells of the foam more so the cells will get thin­ner. This makes it lighter, but it’s also less durable and has less shape re­ten­tion. “With FlyteFoam, we added or­ganic mi­crofi­bres and Kevlar fi­bres to the com­pound that help strengthen the cells and make the mid­sole very strong. So it’s su­per light­weight, more durable than eva and will per­form longer, as it has good shape re­ten­tion. This means the run­ner will get the same cush­ion­ing ev­ery sin­gle mile.”

As for the fu­ture, Ger­aets be­lieves the de­vel­op­ment in foams will con­tinue since we’re al­ways look­ing to im­prove the weight and the ride of their shoes. “We are al­ready pro­to­typ­ing FlyteFoam 2.0.”

Adi­das BOOST

Based on a ground­break­ing de­vel­op­ment process cre­ated by Adi­das part­ner basf, the world ’s lead­ing chem­i­cal com­pany, solid gran­u­lar ma­te­rial ( tpu) is popped like pop­corn in a stream­ing process and ex­panded into thou­sands of small en­ergy capsules, which make up the footwear’s dis­tinc­tive mid­sole. With their unique cell struc­ture, these capsules store and un­leash en­ergy more ef­fi­ciently.

Head of de­sign for sport per­for­mance James Carnes told Sole Col­lec­tor when Boost was in­tro­duced, “Tra­di­tional shoes us­ing a foam-based cush­ion­ing uti­lize one large piece of foam. The Boost plat­form has taken an en­tirely dif­fer­ent ap­proach – in­di­vid­ual capsules. These lit­tle capsules are moulded to­gether, and they re­tain their nor­mal prop­er­ties bet­ter than any ma­te­rial out there. They’re able to ab­sorb en­ergy, and then un­leash that en­ergy at a con­sis­tent rate, over and over.” The other fea­ture of Boost is that it’s not tem­per­a­ture sen­si­tive.

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