Article by Sally Reiley and Sam Winebaum
adidas Adizero Prime X Strung ($300)
Introduction
Sam: The Prime X is truly a “concept car” of run shoes. It is a dramatic and we found highly effective expression of adidas key and highest performance technologies. Its Lightstrike Pro midsole is amplified to 50mm at the heel so beyond the “legal” stack heights limits set up by World Athletics for international competition shoes and then it is topped with a unique data driven Sprung upper.
Not only do we have about 10mm more supercritical Lightstrike Pro foam than their top legal racer the Adios Pro 3 (RTR Review) to come in at a massive 49.5 mm heel / 41mm forefoot we also have a dual “plate” design with Energy Rods plus what appears to be a hardened foam plate (purple) above the outsole.
The look is extreme and Sally and I found the resulting ride equally dramatic and exciting! Please read on for our full review.
The Prime X Strung upper from adidas FutureCraft initiatives is the key upgrade over the 2021 Prime X of 2021, the 2021 version having a Celermesh mono mesh and overlays construction.
The actual fibers are not only differentially placed for varying density but are of different characteristics based on purpose and are oriented in different directions. The upper is coded and laid down thread by thread based on the data. Adidas describes Strung as follows: “STRUNG, (is) an industry-first textile and creation process that allows us to input athlete data into the precision placement of each thread in any direction we choose. We can build and test different structures in the software before sending our chosen design to the STRUNG robot, which places each thread into a single composite with specific performance zones and properties”. The picture below from adidas illustrates the Strung robot. I think in addition to laying down each fiber the fibers are heated and melted together.
I am hoping this new upper (as no changes underfoot are called out) provide a more stable and secure hold than v1’s did where combined with the giant stack and narrow platform the ride was sensational but one had to be constantly focused and aligned to stay “upright” taking away from the incredibly energetic and fast ride experience not to speak of shoe practically.
The second upgrade likely a result of the Strung upper is an approx 17g / 0.6 oz drop in weight for a US9 from v1 to a remarkable 8.68 oz / 257g in my US9 sample.
Pros:
Most unbelievable sensation of flight that I have ever experienced in a running shoe. Sally/Sam
Dramatic, very fast ride with huge smooth rebound off the forefoot. Ever? Sam/Sally
Massive forgiving cushion that is not in the way of speed. Sam/Sally
Energy Rods and plate come across as more flexible, much easier to roll than in the Adios Pro 3 or even Boston 10/11. More front foam stack, softer plate and rods? Sam
Remarkably light 8.68 oz / 257g US9 for the giant 49.5/41 stack height Sam/Sally
Paces always faster and easier than expected Sam/Sally
Approx 17g / 0.6 oz drop in weight US9 from v1 Sam
A tremendous upper for a high volume foot. Sally
While not quite perfected in volume the Sprung upper is clearly more supportive than v1’s Celermesh leading to a “safer” ride making the Prime X more practical and useful for more runs: Sam
Excellent traction with grippy Continental rubber outsole. Sally/Sam
Easy to pull on with wide tongue opening and convenient fabric heel tab, easy lace adjustments. Sally/Sam
Cons:
Upper volume is excessive at listed true to size even if surprisingly well held by Strung. Sam/Sally
Given the remarkably low (and lower) weight a real heel counter, or more rear platform width to stabilize the rear on the narrow platform would be helpful. Sam/Sally
Sadly, very sadly “illegal” for international competition due to 10mm excess stack and dual plates. Sam/Sally
Very expensive for a shoe that is limited to training purposes due to its “illegal” status for racing. Sally/Sam
Stats
Sample Weights:
men’s 8.68 oz / 246g US9
women’s/unisex sizing : 8.1 oz / 231 g US M7/W8 EU 40 UK 6.5
V1 257g / 9.08 oz US8.5
Stack Height: 49.5 mm heel / 41 mm forefoot, 8.5mm drop
$300. Available now. Unisex sizing
Prime X Strung Video Review
First Impressions, Fit and Upper
Sally: My first impression was wow, look at the stack of this shoe, but also wow, check out this cool upper! The fabric of the upper looks like it was created in a sail loft right here in my hometown of Marblehead, MA, “yachting capital of the world,” or at least out of recycled sails. And the shoe just LOOKS fast. I eagerly slipped it on my foot, and then had to double check the size tag: yep, it read US M7/W8, but it felt like an easy half size larger, if not a full size larger.
It seems to run long and is more than a bit roomy. So thick socks it will be for my first run!
With those thick socks on, the fit is quite comfortable for me with no hot spots.
The ankle collar is just the right height for me, and there is comfortable cushioning inside the sides of the ankle opening. The minimal tongue is thin but I did not feel any irritation from the laces, and it is stitched to the lateral side of the upper so it does not slip.
The laces look like traditional old school cotton laces (though I am sure they are not) but they do make for easy adjustments, in my case tightening to better secure my foot, and they are of the right length with the extra lace loop used (I needed to use the extra hole to hold my foot in better and with hopes to better secure the heel).
The fabric of the upper is fascinating: so many woven strands in patterns applied by robots to optimize the performance on a human foot, each strand of varying densities and going in varying directions.
It indeed looks like a racing sail for a high performance sailboat: sails these days are made of woven composites of different fibers of Kevlar, Mylar, Spectra, etc.
Sam: While the prior Celermesh upper was a fine looking “patchwork” of overlays and underlays on a mono mesh here we have a single one piece upper and a unique one. The upper is built up of fibers of differing types laid down in differing densities via layering and even in differing directions to provide support, flexibility and breathability.
For example, notice the pattern and layers of the toe box as shown below vs the lace up area as shown below.
The white fibers are softer and less dense while the gray fiber layers over white fibers below create a thicker more supportive layering and at the fiber level are slightly more rigid.
I can also well imagine there is far less waste printing fiber by fiber than cutting patterns of material and overlays and then assembling. Less labor, more robot construction here.
The fit and feel is smooth, consistent and light on the foot but this is not a soft super pliable upper and that is a good thing given the stack to be supported,
As Sally says the lace up is not only easy but comfortable and highly tunable.
Eliminating the more traditional outer band of material for eyelets the laces run through stiffened cord loops which are part of a narrow inner webbing band which is also stiffened.
Notice the gray fibers radiating from lace up radiating both downwards and to the front with their density increasing at the lace holes. Together they create a very solid lockdown in that area.
The midfoot is secure as well but again we have high volume.
The toe box is generous, very generous but somehow well held despite the overall high volume. In the photo below there is some folding of the toe box as unlike the left I did not put an extra thin sockliner on top of the glued in one.
The heel area is where the Sprung concept starts to suffer a bit. The very dense gray fibers do a very adequate job and far better job than the v1’s upper in stabilizing the heel on the very narrow platform but even though the “purity” of the concept is important I wish for a bit more of a “real” heel counter.
v1 had more rear stiffening but not nearly as stable a hold as here with the densest array of fibers around the back of the heel, then slightly less towards the front and radiating from lace up clearly improving rear stability and hold including at the midfoot.
The issue with the upper for me is not the materials or the Sprung approach but its overall volume, and the aforementioned lack of a heel counter . I am a half size up from my normal in the sample and had to wear thick thick Darn Tough merino run socks to “fill” the space. I also tried a thin sockliner over the top of the glued in stock one which clearly also took up some of the space and gave me, in combination, an adequate overall hold.
I for sure would go true to size and maybe a half size down for my narrow to medium feet with thinner socks. If you have high volume broad feet true to size should work fine
Midsole
Sam: The midsole is a 3 layer Lightstrike Pro construction with Energy Rods and apparently also another set of lower road of what appears to be hardened purple foam or plastic.
The top layer is slightly softer than the bottom layer allowing for a soft landing feeling and then as it plunges and gets thicker upfront for the foot to sink in and roll forward, meet the Energy Rods and rebound. The foam and and I think rod and plate construction is considerably more forgiving, has more distinct rebound and is much easier to roll forward and bounce away than the Adios Pro 2 or 3, shoes designed for elites and their strong forefoot to mid foot strikes.
Here too the narrow rear platform plus high stack height is not ideal for pronounced heel striking at slow paces. To illustrate the difference in rear platform widths the considerably more heel stable Nike Alphafly 2 has a maximum heel platform width of about 95mm in my US8.5 whereas the Prime X is at 76mm (as is the Adios Pro 2).
That said it is so easy to find the forward groove and roll with a bit of focus on a forward lean (yet less than v1) the geometry is quite neutral to foot strike unlike most super shoes.
While the Prime X is a rigid rocker with no flex unlike most super shoes it actually runs more like a shoe with some flex with a smooth flow forward and then an incredibly powerful and pleasing rebound and spring to toe off. Unlike the Pro it is not rigid and prescriptive with that shoe’s angular feel up front.
I suspect the Energy Rods are more flexible in this mix and I for sure like that with purple rods layer providing nice stability and a consistent platform for toe off. I have never sensed any plate harshness given the Energy Rods sit more or less with 20mm of Lightstrike Pro above and below towards the front of the shoe, a key advantage of the 10mm more stack height overall.
The cushioning… Incredibly deep, protective and energetic. A rush!
Soft without being sloppy or mushy with much more soft rebound than say an Adios Pro 2 or even the now softer Pro 3 with their now slightly firmer foams with what I sense as more mellow Energy Rods in the mix a huge plus in keeping the midsole energy high and the flow smooth.
Sally: Simply put, there is a lot of midsole here. Three layers of Lightstrike Pro foam contribute to a whopping 49.5mm heel stack. This is the over the top amount of cushioning you never knew you needed! And I won’t need high heels anymore to see eye to eye with taller folks at a cocktail party. Seriously, the massive midsole in combination with the energy rods is the magic that makes this shoe so much fun to run in.
Outsole
Sally: The outsole checks all the boxes for me: it was relatively quiet underfoot (hear that, obnoxiously loud Alphafly); the Continental rubber covering the entire forefoot is sticky and provides great traction, and there are no “gravel grabber” grooves or holes to collect small rocks and pebbles in.
There are three oval shaped openings under the ball of the foot revealing the purple plate. Continental rubber has a reputation for durability, so I am not worried about that with this outsole.
Sam: Not much to add to what Sally said. Continental rubber is always excellent and here the front tightly spaced ridges not only provide a stable landing but some miles or road base with a bit of loose and gravel over had excellent grip, better than most road shoes I have run on the same terrain.
Ride
Sam: The ride is staggeringly fast, energetic, and forgiving. Every run has been considerably and very considerably faster than expected, planned, or based on perceived effort.
Out of the box I easily ran my fastest (short) training run of the year well below 8 minute paces. I also took them for a 6.39 mile all uphill run (421 feet / 128 meter gain) run at 2000 meter plus altitude in Park City at 9:01 pace smooth as can be. OK the last mile was a bit shakier but I was fine on earlier sections of packed road base gravel thanks to the Continental rubber and adequate stability.
They climbed extremely well for such a giant shoe but as with v1 steep downhills due to the high narrow platform will not be the Prime X's forte if you can't really lean forward. They ride best and fastest for me on flats and gentle downhills
The cushioning is truly bottomless, protective and soft but in no way mushy clearly returning energy and more noticeably so especially at the forefoot than any shoe I have ever run, and I am relatively slow and old hoping for a sub 1:40 half this year. There is tremendous, quite stable rebound off the front of the shoe with the dual propulsion elements well cushioned and easy to activate.
There is no midfoot “plate” hump (Puma FAST-R), need to overly land direct on the midfoot/forefoot (Alphafly 1 and Metaspeed Sky 1) or low feeling overly soft heel (RC Elite 2). The narrow rear platform and voluminous upper fit for my narrower foot does require attention on the run (but less for sure than scary v1) and overall the rear of the shoe is not as stable as I would prefer and this was most noticed when tired. Focus and a forward lean into the front of the shoe is required to keep things steady. Yet, compared to the Prime X 1, a similarly energetic but “scary” ride we are more stable here likely due to the better midfoot and rear hold of the new Strung upper, and this despite its volume.
Bottom line: This may be the fastest most exciting ride ever for me in a running shoe just wishing the shoe was a touch more rear stable. A real heel counter likely would help.
Sally: With its insane stack height of 50mm and three layers of Lightstrike Pro combined with a significant rocker geometry, this shoe provides a running experience like no other. As Sam says, STAGGERING FAST, ENERGETIC, and FORGIVING. With one week to go before the London Marathon, I am trying to do slow, easy taper training runs, but have found my paces have been so much faster than planned with no additional perceived effort.
These shoes want to fly, and they truly come closer than anything else I have ever worn to giving you that amazing feeling of flight.
They say that elite runners spend more time in the air than on the ground, and on the ground time is like applying the brakes; well these shoes make that in the air time easy. And for such a highly engineered tech design, the ride is surprisingly smooth and natural. It is a bouncy, soft but not at all mushy ride, and it transitions very smoothly from midfoot to forefoot with a delightfully natural feeling toe-off. My only issue with it was the lack of stability in the heel, where sharp turns felt dangerous with my heel slipping sideways in the shoe. Of course, sizing down to a tighter fit would help this stability issue quite a bit.
Conclusions and Recommendations
Sam: Adidas pulled out all the stops here to deliver a spectacular riding and very fast shoe that also delivers a wonderfully pleasing experience like no other I can think of. So energetic and forgiving and so light for all its forgiving cushion. The Energy Rods and plate are never in the way and play brilliantly with the 41mm of front foam delivering tremendous relatively stable rebound at both fast and relatively fast training paces. It should be noted the Prime X is not designed for slow paces back on the heel.
Oh I wish it was any any runner including elites race “legal” and had less upper volume or a bit more rear platform width to keep things slightly better aligned as it clearly would be my first half to marathon choice if not 10K choice and I have tested every 2022 super shoe but for the Metaspeed Sky +.
At $300 adidas is way up there for a shoe that, while it makes me smile like no other. Sadly (at least for now) it is not race legal (at least for top elites) which would make it an all around home run and a better value. adidas should really consider applying this softer, less rigid, bouncier approach in a race legal shoe.
The Strung upper and its fiber by fiber multi directional data mapped construction absolutely does its job (in comfort and most of its hold and must be key to bringing down the weight of this massively cushioned shoe to 8.68 oz / 246g US9. But.. the upper is in my view too voluminous and could use a real heel counter. Well worth the weight “gain”. My sample is a half size up from my normal and I had to resort to very thick socks and a second thin sockliner to get a secure fit and even then things were not ideal due mostly I think to the lack of a heel counter or a slightly wider rear platform width. Broad high volume feet should be fine.
To conclude the Prime X Strung is like no other run shoe. Fast, fun, forgiving and with as a special experience of flight as Sally says and with it all amplified to the max.
Sam’s Score: 9.48 /10
Ride: 9.9 Out of this world!
Fit: 9.1 But for the volume issue, sizing and lack of heel counter, Strung tech is a keeper
Value: 8.7 $300.. and also affected by not being race legal
Style: 10 Love the look here.
😊😊😊😊😊
Sally: Wow. This is the shoe that makes running FUN. And not just because it is the fastest shoe I have ever run in, but it provides a unique running-is-flying sensation that is a real joy to experience. The 50mm stack height is insane but somehow the three layers of energetic Lightstrike Pro foam and the rocker combine to provide a very natural and smooth ride. Boy, so I wish I could wear these shoes to race the London Marathon this week! If only they were legal, and if only they were a size or two smaller than my usual size, I would be lacing them up in London and at every future 10K, Half, Marathon, whatever. They make harder paces feel easy and your times faster than the perceived effort would indicate. The caveat is that they are not all that stable, so stick to the straight even roads and forget cobblestones or rough surfaces. They are ideal for an uptempo run or a long distance training run. If you can afford a $300 shoe to make those long training runs fun, and/or if you want a confidence booster, get yourself a pair! You never knew you needed a super max cushioned aircraft like this on your foot.
Sally’s score: 9.7 /10
Ride: 10.0 To infinity and beyond!
Fit: 9.3 I could give it a very low score because they are so not-true-to-size, but with some labeling adjustments on their sizing, the fit would be comfortable. Still a bit overly generous in the forefoot volume
Value: 8.5 ($$$ for a shoe that is not legal for racing, and the temptation will be to race it - believe me, I know)
Style: 10.0 Gorgeous
😊😊😊😊😊⚠️(that’s the max score for how pleasing/fun the experience on the run, followed by a caution sign for instability)
Comparisons
Index to all RTR reviews: HERE
Prime X v1 (RTR Review)
Sam: The key differences are uppers here. The Strung upper while voluminous at marked sizes has better overall hold especially midfoot to rear of shoe eliminating quite a bit of the instability of the v1's upper where total focus was required at all times to stay aligned on the platform. Now less so. The second key difference is weight. The Strung upper reduces the weight of Prime X by a big 0.6 oz /17g drop in weightAdidas Adios Pro 3 (RTR Review)
Sam: The Pro 3 shares many underfoot similarities with the Prime X with Lightstrike Pro foam, Energy Rods and Continental rubber. The Prime X amplifies and increases the cushioning, softens the ride and is easier flowing with far more bounce and run pleasure and for me is clearly a faster ride. Strange but true as the Pro 3 is the top end elite shoe with many victories to its credit and I ran a fine 4 mile race in them but in the end is overly aggressive, angular, and favors elite level speeds and strong mid to forefoot strikes, something I and most of us don’t have. For racing, if it was legal, I would pick the Prime X any day of the week for all distances as it so much more energetic and so much easier to run fast for me. I was true to size in the Adios Pro 3 and I think with thin socks I might size down half a size in the Prime X.
New Balance FuelCell SC Trainer (RTR Review)
Sally: (W8 in both) I love the SC Trainer and have enjoyed several 20 mile runs in it this marathon training cycle. It is smooth and quick and bouncy, and like the Prime X, has an “illegal” stack height of more than 40mm (47mm). The new Energy Arc system seems to work well.
The Prime X notches up both the fun factor and the speed factor with its 49.5mm stack and the Energy Rods really work for me. The SC Trainer is heavier but more stable (the upper fits me much better); the Prime X might be a bit more wild, and is lighter and quicker in flight. I attribute much of the instability of the Prime X to the ill fit of the upper, in my case compounded by a size too large (NOT true to size).
Nike Zoom X Alphafly 2 (RTR Review)
Sally: (W8 in both) I recently bought myself a pair of Alphafly 2 believing the hype that this is the shoe to PR the London Marathon in, but… I will not be wearing it after all. I really want to love the Alphafly 2, but am struggling with getting it to work for me. The arch does not bother me as it does so many runners, but I am concerned the length runs short for a marathon effort and my big toenails might be sacrificed at TTS (I typically size up half size in Vaporfly for this reason, but heard that the Alphafly 2 has a generous fit and there was no need). The Alphafly is also ridiculously loud (2 not as much as 1, but still annoying).
The Prime X is bouncier and smoother and lightning quick and more fun for me, albeit a bit wild. But… the Prime X is not legal for racing. I think the fit of the upper will decide which works for you for your long runs (and races).
Sam: More stable, more secure and strange to say for the recent world record marathon shoe the Alphafly is more ponderous and a safer bet. While highly dynamic and tuned for racing its experience is not nearly as exciting (or fast for me) as the Prime X but is a safer and race legal bet. Both have roomy uppers with the Alphafly more secure overall and truer to size having a more foot conforming fit than the Prime X.
Xtep 160X 3.0 Pro (RTR Review)
Sam: The Xtep is another pleasing giant of a super shoe and one which as far as we know is race legal. With a max 40mm heel and 4mm drop so a 36mm forefoot it has plenty of cushion especially at the forefoot as the Prime X does. Its expanded pellet TPU foam is somewhat firmer and its plate more present in feel but still easier to roll than many competing super shoes so as with the Prime it can also serve as a trainer. While a very energetic riding shoe and super fun it is not quite the total rush and rebound sensation of the higher stacked Prime. Its upper and rear winged carbon plate makes it one of the most stable super shoes and more stable at the rear than the Prime X. It’s upper fit is fuss free and try to size with an extra set of sockliners included, something adidas should consider for Prime X. At $190 it is a better and more practical value and one of our favorite super race shoes of 2022 but does not quite deliver the incredible and fast experience of the Prime X for me.
The Prime X Strung is available at adidas on September 29. $300
Tester Profiles
Sally is a lifelong runner and mother of five who agreed against her better judgment to run her first marathon at age 54; she has since run the past nine Boston Marathons, two NYC Marathons, and one Chicago, with the WMM Six Star Medal now in her sights. With a Boston PR of 3:25:55 in 2022 (9th place in AG) and two consecutive 2nd place in Age Group awards in NYC, she is about to run in the Abbott World Marathon Majors Age Group World Championships at the London Marathon on October 2, 2022 (W60-64). She also competes in USATF races with the team Greater Lowell Road Runners (5K, 10K, 5 Mile, 10 Mile, Half Marathon, etc). To add meaning to her Boston Marathon races she runs with Team Eye and Ear and has raised over $260,000 for Massachusetts Eye and Ear Hospital. Sally is a compact (petite) runner at 5’2’’ and 105 pounds and lives in Marblehead, MA, training outdoors year round.
Sam is the Editor and Founder of Road Trail Run. He is 65 with a 2018 3:40 Boston qualifier. 2022 will be Sam’s 50th year of running. He has a decades old 2:28 marathon PR. These days he runs halves in the just sub 1:40 range if he is lucky, training 30-40 miles per week mostly at moderate paces on the roads and trails of New Hampshire and Utah. He is 5’9” tall and weighs about 164 lbs, if he is not enjoying too many fine New England IPA’s.
Samples were provided at no charge for review purposes. RoadTrail Run has affiliate partnerships and may earn commission on products purchased via shopping links in this article. These partnerships do not influence our editorial content. The opinions herein are entirely the authors'
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8 comments:
But the shoe is legal if one does compete as non-elite or am I wrong here?
Interesting transfer of technology with the upper's construction. This manufacturing technique is widely used in the hi-tech composites industry, where reinforcing fibres are robotically plied in an optimal orientation to provide strength in the areas where needed. Weight-saving is realized by the ability to eliminate fibres in areas where strength is not required, as with traditional uppers e.g. a woven mesh or knit.
I came to write the same comment as Striezi, as long as it's used for non-elite races, my understanding is that it's legal (or at least tolerated since no one will verify)
Quote from another website : "The Prime X, on the other hand, is perhaps the first super shoe that is exclusively available for regular joe runners, at least in a race setting. When asked about amateur runners wearing “illegal” footwear, a representative from the Boston Athletic Association gave me the following official statement: “The Boston Marathon follows rules and guidance established by World Athletics and USA Track & Field. All professional athletes will undergo uniform and shoe review to ensure compliance with all rules.” An official at another well-known marathon told me that runners in the non-professional fields do not need to abide by the regulations set forth by World Athletics, but asked not to be quoted on the record."
Is the tongue gusseted in the Strung and in the original model?
I’m a forefoot striker. Will this fact eliminate the stability problem in both of these models? My running route is straight, no sharp corners.
Hi. Thanks for an interesting review. I use the Vaporfly 2 for racing and the Adidas Ultraboost 2020 for my daily mileage. I use a size 10,5 UK. They’re just right. Not roomy nor too snug. Should I stick with that you think or go down to size 10 UK?
I would go same size, I got my normal size and they are fine, not too tight, maybe a bit roomy compared to vaporfly v1
Ok so I went for a tempo run with the Prime X strung and they are fine but I would not say as bouncy as the Tempo Next. I also noticed/think the "stress" is not on the same muscles as other shoes. Because of the stack height and all the foam, it seems the impact forces are quite different and it seems it triggered muscles in the thighs were more sollicited. They ankles as well. Many people say the lightstrike pro benefits of a break in period so we will see. This being said, I have never been a fan of lightstrike compared to Nike zoom x foam and pods.
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