adidas adizero Prime X3 Strung Review
By Matthew Klein
adidas adizero Prime X3 StrungPrice: $299.95 at Running Warehouse
Weight: 10.9 oz, 310 g (men's size 10)
Stack Height: 50 mm heel / 43 mm forefoot
Drop: 7 mm
Shoe Purpose: Super Trainer
Pros: Slightly Wider, Comfortable Fit, Bouncy Heel, Awesome Long Run Shoe
Cons: Lace Bite, Less Stable Midfoot than Prior Version
RUNNING SHOE SUMMARY
The adidas adizero Prime X3 Strung is a super trainer for those who want the ultimate super road shoe for training, long runs and long workouts. A strung upper provides a slightly wider fit that is secure enough that tightening the laces is not necessary. A super stack of newly-updated Lightstrike Pro foam provides an incredibly bouncy/responsive heel and a fast rolling forefoot. Heel strikers with mostly neutral mechanics wanting a faster, leg-saving tool for long runs, long workouts and long races (if you are not a a pro) will find this shoe faster and more responsive than the prior version.
SIMILAR SHOES: Hoka Skyward X
PAST MODEL: Adidas Adizero Prime X2 Strung
FIT
(To learn how a shoe should fit, check out our full podcast on fit by Matt Klein.)
Matt: The adidas adizero Prime X3 Strung fits me true to size in my normal men's US size 10. I was worried when I tried the Prime X3 initially that it fit short due to how low the upper was especially in the forefoot. This has stretched out slightly with time, although the upper still sits low over the toes (especially the big toe) and some people may need to go up a half size. While the volume is low, the fit in the forefoot is slightly wider. Unlike the snug fit of the prior version, there is some wiggle room for the toes side to side. The midfoot shifts to slightly higher volume and a more snug width. The tongue is connected to the rest of the upper and is a more stretchy fabric than the rest of the upper. Despite the higher volume, I would highly suggest not tightening the laces too much. The narrow laces easily pinch the top of the foot and fortunately, the upper stays secure even without tying them too tight. Those with really narrow feet may not do well in this shoe, but those with normal to even slightly wider feet will do better. There is also no last lace hole to lace lock the shoe.
Fortunately, the heel is more snug thanks to additional internal padding. The heel collar comes up higher than average with collar padding around the entire heel. This seems to help prevent heel slippage and adds security. There is no heel counter, so those with haglund issues should do well. The security is fairly good once you get used to the unique upper. However, the inner aspect of the upper is rough, so socks are absolutely required with this shoe. I would suggest thicker socks due to the inability to tie the laces too tightly and how high up the heel collar comes. Once you get going on the run, the upper does disappear.
Typical Size: Men's US Size 10
Shoes that have fit Matt well: On Cloudboom Strike, Asics Gel-Nimbus 27, Xero HFS, Topo Cyclone 3, Adidas Adizero Evo SL
Shoes that have fit snug: Hoka Arahi 7, Brooks Launch 11, Diadora Mythos Vigore 3
Shoes that have fit large: Salomon S/Lab Phantasm 2, Adidas Agravic Speed Ultra
Doctors of Running Checklist
Is This a Good Shoe for Walking: No
Is This a Good Shoe for Standing: No
Is the Forefoot Flexible: No
How Flexible is the Shoe: Not Flexible
Is This a Good Heel Bevel: Yes
Recommended for Haglunds: Yes
Is This Shoe Orthotic Friendly: No
Recommended for Sockless: No
Durability Expectation: Above Average
PERFORMANCE
Matt: The adidas adizero Prime X3 Strung is a super stack super trainer. There is 50 mm of Lightstrike Pro in the heel and 43 mm in the forefoot. This makes the shoe tower above the ground. The heel is incredibly bouncy and responsive. The forefoot is cushioned but stiff and firmer than expected. There are two stiffening agents in the midsole with a top carbon plate that runs the length of the shoe and bottom Energy Rods 2.0. These ensure there is no flexibility in this shoe at any point. There is some mild toe spring, so those with toe mobility issues may still have to be cautious with this shoe. The amount of stiffness makes the front firmer despite the massive amount of foam. It was actually uncomfortable to land with a forefoot strike until the shoe broke in. After more than 35 miles, it still feels like a heel strike is required to get the most bounce and responsiveness out of this shoe.
Fortunately, the bouncy midsole does make the shoe feel lighter than the 10.9 oz weight I measured in my size 10. This weight is more in line with cushioned trainers, but the responsiveness of the midsole offsets this, as long as you land at the heel. The heel transition is super smooth and bouncy thanks to a massive posterolateral bevel. Landing at the back propels you forward quickly through the midfoot and right off the forefoot. If you land with a rearfoot strike, the transition through the forefoot is snappy and quick. The longer forefoot rocker compared to prior versions makes this shoe feel really efficient at longer and uptempo efforts. It is really easy to get into a quicker rhythm for long runs and this has been my go to shoe to keep up with my wife on our uptempo long runs (she forgets that I am currently pushing a ~60lb stroller with my daughter). The bounce of the midsole does allow this shoe to go down to tempo paces, but the large size of the shoe makes it feel too bulky to work for faster efforts or intervals. For that reason, this shoe maxes out at half to full marathon pace, but holds those paces extremely well for long periods. This shoe can be used for easy runs, but the forefoot needs some time to break in for that. I personally would prefer normal trainers for easy mileage, but this shoe can do all of that.
It appears to have the durability to handle daily miles as well as after 35 miles, there is no wear on the outsole. The Lighttraxion outsole is holding up extremely well, although I am slightly concerned that I may tear it off as it splits in the midfoot. Thus far, it is holding up well and while the midsole has broken in, it has not lost any of its bounce over these miles. I therefore expect a higher than average number of miles out of these compared to other super trainers, but will continue to get miles to see how that partial outsole holds up. Surface-wise, this shoe should only be used on stable road or track. Any unstable or soft terrain is not great as this shoe towers over the ground. Even small bumps in the road can be rough, so while this is a great uptempo long run and potential longer race shoe for many people, it has strict surface requirements.
STABILITY
(Learn more about stability in our full guide)
Matt: The adidas adizero Prime X3 Strung is a neutral shoe with stability mechanisms in the heel and forefoot. The heel features a large posterolateral heel bevel that guides heel transitions lateral. Those with mild medial stability needs in the rearfoot will do well here as the shoe emphasizes lateral motion. Those with lateral ankle sensitivities will not do well. The midfoot tapers slightly and is fairly neutral due to the slight medial cutout. There are small sidewalls on both sides of the shoe that run the length of the shoe, but they are minor and don't make much of an impact on the midfoot. At faster speeds, the transition through the midfoot is fast enough that this isn't the biggest deal, but there is little there to stop the midfoot from collapsing over the medial side. The forefoot is the most stable part of the shoe as it is wide, extremely stiff and the forefoot rocker is biased laterally. This creates a laterally guided forefoot transition, which is great for those with medial forefoot stability needs. However, those with lateral forefoot stability needs may struggle a bit with that final transition.
Overall, the guidance isn't terrible for those with medial stability needs, except for those with significant stability needs in the midfoot. I have been able to do long runs in this shoe, which is one of the most telling signs about how stable a shoe is. I start to fatigue toward later miles, but don't get the same discomfort I experience in normal neutral shoes. However, the amount of lateral bias in this shoe does start to get fatiguing with longer miles. For those reasons, those with medial heel and forefoot medial stability needs will do best. Those with neutral needs will likely do fine but will still need to train in this shoe to prepare for the towering general instability prior to any intense efforts.
Thoughts as a DPT: Midsole Bending Stiffness and Compliance Perception
By Matthew Klein
The adidas adizero Prime X3 Strung may have one of the stiffest forefoot designs on the market. Tall stack height shoes with tons of material underfoot already provide resistance to bending, adding inherent stiffness. This is one of the reasons why a shoe like the ASICS Superblast 2 is so stiff despite not having a plate. However, not only does the adidas Prime X3 have a tall midsole, it also has two layers of stiffening agents. A top layered carbon fiber plate runs from behind the heel to what appears to be under the metatarsal heads (forefoot). A plate that is really close to the foot may actually increase toe extension (MTP joint extension) and ankle plantarflexion, things that are often reduced in highly rockered, plated shoes (Flores et al., 2021). This is a compensation to get over the increase in stiffness underfoot that occurs with a plate, especially one close to the foot. In addition, there are also carbon fiber rods that extend into the bottom aspect of the midsole. This adds even more stiffness, particularly with two different levels of stiffening agents. Previous research has been able to suggest what differences occur with placements of the plates either close to or farther away from the foot, but not both at the same time. What it feels like is that the midsole ends up feeling so stiff that the forefoot feels firm. You can have a ton of cushioning underfoot that under none-plated circumstances feels soft, yet it will still feel firm when a plate or plates are present because of the added stiffness.
It is for these reasons that the Prime X3 Strung feels particularly firm in the forefoot despite how much cushioning there is. When looking at shoes to predict their compliance or cushioning, do not just look at the type of cushioning and how much there is but also look at the presence of stiffening agents.
Flores, N., Rao, G., Berton, E., & Delattre, N. (2021). The stiff plate location into the shoe influences the running biomechanics. Sports Biomechanics.
RECOMMENDATIONS
Matt: The adidas adizero Prime X3 Strung has been a fun shoe to do uptempo long runs in. It improves on version two with a faster ride that doesn't feel as clunky, but loses the incredible consistent stability. The shoe is still heavy, despite a large cut out of the midfoot midsole and I have some outsole durability concerns due to the split midfoot. While it is fun, it is absolutely not a shoe for everyone due to the cost, stiffness and aggressiveness of the shoe. My major suggestions are to return to a full ground contact outsole, reinforce the medial midfoot a bit more and improve the bounce in the forefoot. While I understand that a wider and more full ground contact midfoot may increase weight, the central midfoot midsole cut out demonstrates there may be other ways to reduce weight. A shoe this tall needs to have a wider sole to offset the tall and soft midsole, which brings inherent instability. A split midfoot also means potential durability issues for runners like myself who may start to scuff their feet with fatigue. Given this shoe is meant for longer distances, it may be worth the little extra outsole coverage.
Finally, I think the forefoot may be too stiff. I cannot really appreciate the forefoot unit of Lightstrike Pro because the plate and rods add so much stiffness that the shoe feels firm. This is great on faster efforts, but can be a bit problematic while breaking in and when fatigue sets in. If this could be softened even a little, it would improve comfort and may make this shoe feel better for forefoot strikers as well.
WHO IS THIS SHOE FOR?
Matt: The Prime X3 Strung is for heel/midfoot strikers who want the tallest and bounciest shoe for longer uptempo efforts and distance races. The midsole will work best for those who want the tallest possible shoe with a bouncy heel combined with a stiffer forefoot. The upper will work best for those with normal to slightly wider feet who want a shoe that don't need to (or can't) tie the laces too tight. The ride will work best for long runs, uptempo efforts and half to full marathon road races (as long as you are not a professional athlete). Those interested will also need to cope with the $300 price tag, which is becoming more common among super racers but makes this the most expensive trainer/racer on the market.
For me, this has been purely an uptempo long run shoe. It can hold uptempo paces really well but has such a unique space that it makes the justification for purchasing it difficult. However, those wanting the most responsive trainer or those who are losing foot/ankle function related to forward progression will still enjoy this shoe. It truly is a tool to maintain forward progression and those who use it I would highly encourage you to spend some time barefoot or in less shoe at some point during the week due to its extreme nature. Those with hip instabilities, sensitivity to laterally biased shoes and those with midfoot stability needs will not do well in this shoe given its maximal stack height and clear biases in movement.
It is still an interesting shoe that I will continue to get miles on, but the higher weight is something that may not be able to be overcome with a shoe this tall. It improves on the prior version by being faster and is far more stable than the original versions, so one could argue this is the most "balanced" version in regards to speed, stability and fit of all the versions so far. Where Adidas goes from here... I am curious to see.
GRADES
Matt
Fit: B+ (Wider but secure fit with no heel counter. Lack of tongue padding causes some lace bite on top of the foot, but fortunately, the laces do not need to be tied for security)
Performance: A- (Bouncy heel with firmer/snappier forefoot. Best for long uptempo runs and efforts, including marathon-type races for non-pros. A great shoe for locking into a pacing and going for miles)
Stability: B+ [Neutral with Medial Stability/Lateral Bias at Heel/Forefoot] (Extreme lateral heel bevel and lateral forefoot rocker create medial stability at the heel/forefoot while the midfoot is neutral)
Value: B- (Extremely expensive but unique performance-focused ride. Durability seems good so far but more miles are needed to see if it can hold up to how long version 2 lasts)
Personal: B+ (My go to long run shoe. Forefoot needs some time to break in and unsure of outsole durability. While the ride is faster, it is a little less stable than the prior version. Still coming to terms with the $300 price tag, but it is a solid shoe outside of the lace bite. )
Overall Design: B+
SHOP | SUPPORT DORPrice: $299.95 at Running Warehouse
adidas adizero Prime X3 Strung
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FURTHER READING
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