Adidas Ultraboost 5X Review
By Matthew Klein
Adidas Ultraboost 5xPrice: $179.95 at Running Warehouse
Weight: 9.6 oz, 272 g (men's size 9), 8.8 oz, 249 g (women's size 8)
Stack Height: 38 mm / 28 mm
Drop: 10 mm
Shoe Purpose: Performance Training Shoe
Pros: Comfortable Primeknit Upper, Snappy Midsole
Cons: Rearfoot Clunky Due to Posterior Flare, Midsole Firmer than Expected
RUNNING SHOE SUMMARY
The Adidas Ultraboost 5X is a performance trainer for those who want a high drop, snappy ride with uptempo capabilities with a flexible Primeknit upper. The new LightBoost 2.0 provides a slightly firmer but snappy and responsive ride underfoot that feels better at uptempo efforts. A new mono Primeknit upper provides a snug but comfortable hold on the foot with a classic split heel design that will work great for those with Haglund issues. A large posterior heel flare makes this a shoe that works better for uptempo efforts, the Ultraboost 5X is the first true performance trainer in the Ultraboost series.
SIMILAR SHOES: New Balance FuelCell Propel v5
PAST MODEL: Adidas Ultraboost Light
FIT
(To learn how a shoe should fit, check out our full podcast on fit by Matt Klein.)
Matt: The Adidas Ultraboost 5X fits me true to size in my normal men's US size 10. The upper is a full-length mono Primeknit, which provides a thin, sock-like fit with plenty of stretch. The volume is quite low across the foot in the upper but there is some stretch particularly in on top of the foot. The width is normal with a wider base but the lower volume keep things average. This transitions into a slightly snug midfoot thanks to the compressive knit upper. The tongue is integrated with the upper, although I experienced some bunching of the tongue in the center that I had to carefully lay down. The laces did add some security but were not completely necessary due to the compressive nature of the upper. This only applied with forward to back motion as side to side motion required the laces and still had some sliding. The knit upper keeps the foot on the platform as long as you are moving forward. This is a great example of a shoe that should only be worn for running and not for other sports that require lateral motion. Quick turns do cause sliding inside the shoe, so this is a shoe that should only be used on mostly straight courses. The heel fits slightly snug with mild heel collar padding. There is only two external heel counters that sit on the medial and lateral sides of the heel. There is nothing besides the upper at the back of the heel, so those with Haglund deformities should do extremely well in this shoe. The upper requires socks as the tongue guard is internal and can easily catch the foot. Socks fix this, so make sure your foot is covered at least partially if you are interested in this shoe.
Typical Size: Men's US Size 10
Shoes that have fit Matt well: Saucony Guide 17, ASICS Kayano 30, Hoka Gaviota 5, Saucony Endorphin Elite, Nike Ultrafly
Shoes that have fit snug: Hoka Arahi 7, Saucony Kinvara 14
Shoes that have fit large: Salomon S/Lab Phantasm 2, Altra Timp 5
Doctors of Running Checklist
Is This a Good Shoe for Walking:
Is This a Good Shoe for Standing:
Is the Forefoot Flexible: No
How Flexible is the Shoe: Mildly
Is This a Good Heel Bevel:
Recommended for Haglunds: Yes
Recommended for Sockless: No
Durability Expectation: Above Average
PERFORMANCE
Matt: The Adidas Ultraboost 5X is a performance trainer for those who land a little farther forward. The full-length LightBoost 2.0 foam provides a slightly firmer and more resilient ride underfoot. The weight is lighter than previous versions and feels like a lighter trainer combined with the midsole foam. There is a 10 mm heel drop but this feels much higher due to the large heel and large posterior flare. The heel transitions are somewhat clunky due to the larger heel despite a decent posterior lateral bevel. This transitions into a slightly stiff midfoot and a quick forefoot transition. There is little flexibility at the forefoot at slower speeds but it becomes more snappy the faster you go. There is no plate in this shoe unless you count the torsion system in the midfoot that extends slightly forward and posterior. Regardless, the midsole foam and taller stack height make the ride stiffer. For these reasons, this shoe works far better during uptempo runs than easy runs.
I have found easy runs to be somewhat uncomfortable with the firmness and large heel flare. When I pick up the pace and my footstrike moves forward of the large heel, the shoe feels far smoother and transitions well. This makes the Ultraboost 5X excel during uptempo runs and fartlek-type efforts. It is not light enough for me to consider for race day or faster workouts and the Adizero line is a much better choice for a variety of workouts and races. However, consistent uptempo efforts make this shoe shine.
The outsole durability has been fantastic with extensive coverage across the length of the bottom of the shoe. I have 30 miles on my pair with no wear on the outsole. The traction is fairly average and the Ultraboost 5X is best used on smooth, non-technical road and trail surfaces.
STABILITY
(Learn more about stability in our full guide)
Matt: The Adidas Ultraboost 5X is a neutral training shoe. There are some stable elements that slightly offset this. The external heel counter does provide some centeredness for the rearfoot. The larger posterior lateral heel flare does provide some lateral guidance but it is so far posterior that only extreme heel strikers will be able to utilize it. There are sidewalls throughout the length the length of the shoe on both sides of the foot. The foot sits deeper in the midsole, so this provides some centeredness. However, this is most effective in the forefoot. Those who need mild forefoot guidance from the sidewalls and slightly stiffer ride will do well in this shoe. Those who are heel strikers will notice that the posterior flare causes a push medially at the midfoot. This makes the midfoot neutral, the forefoot mildly stable and the heel mildly stable.
Thoughts as a DPT: The Impact of Heel Flare on Ankle Dorsiflexor Musculature
By Matthew Klein
A posterior heel flare refers to the posterior aspect of the midsole extending far back beyond where the rearfoot sits. This design appears to be particularly common in certain types of casual/fashion shoes and is a somewhat popular design element seen recently in Adidas, Hoka and even Topo shoes. Some of the justification for the use of this design element has been to either lengthen out the contact phase of gait, which supposedly spreads out impact forces or to increase running speeds as it may "push" you forward.
There is limited research on this subject and what little is out there suggests that it increases ankle dorsiflexion angle at heel strike, tends to cause an increase in muscle activation of the tibialis anterior and increase in knee flexion angle. While each person will obviously respond differently to this, basic biomechanics suggest that having a large posterior projection of the heel not only can increase heel strike ankle angle, but it may also increase the velocity of the loading response phase at the foot. The foot absorbs shock through pronation as well as the foot moving from a dorsiflexed position at heel strike (assuming you are a heel striker) to a plantarflexed position.
This requires eccentric work from the ankle dorsiflexor musculature to control the foot down and absorb the impact at heel strike. The faster a eccentric contraction occurs, the greater the force and stress through the muscles. A fast eccentric contraction is the greatest stress muscles will experience and is also the more common type of contraction where injuries occur due to the high forces generated. Having a large posterior heel flare will increase the velocity of the foot traveling from a dorsiflexed position to a plantarflexed position, which based on the type of contraction occur will naturally increase the stress through the shin/dorsiflexor muscles. It is for this reason that this type of shoe may be associated with "shin splint" type pain in runners.
This shoe type is especially common among newer runners who typically use more casual shoes for running and may be a contributing factor (in addition to the body not being trained) to the common development of shin splints in this population. For the above reasons, I (AGAIN) urge footwear companies to stop using this design element as there is little to no benefit to it and I argue that it is instead detrimental.
RECOMMENDATIONS
Matt: The Ultraboost 5X is the first time Adidas has made this shoe into a performance trainer. It is no longer heavy and feels best during uptempo efforts. The upper design is great for those with Haglund deformities given the split heel design. However, the huge heel and posterior flare make the back half of the shoe uncomfortable and has caused extensive soreness at my shin and anterior knee. This is expected given the design but my biggest recommendation is the reduce the heel flare. I understand that designers/developers think this is either a good looking design or provides extra cushioning or a push forward for rearfoot strikers. This ignores biomechanical principles regarding eccentric load, moments and powers at the ankle and knee. I would encourage a return to the large rounded heel in the Ultraboost Lite, which was excellent. Outside of that, the Ultraboost 5X continues the performance trend of the series. I am still confused how this fits with the Adizero line but I am clinician and biomechanist, not a product line manager.
WHO IS THIS SHOE FOR?
Matt: The Adidas Ultraboost 5X is a performance trainer for those who land farther forward and want a good looking shoe that can pick up the pace. The fit is sock-like and while lower volume, does stretch a little. It will still be best for normal volume and normal width feet but those who want a compress sock-like feel will do best here. The midsole foam is firmer/responsive, making it a better option for those who want to use it for uptempo efforts. My first thoughts when I finally figured out how to use this shoe was that it would be great when you want to look good for run clubs/group runs, you don't want to show up in super shoes because you don't want to be "that person" and where you are supposed to be running easy but everyone picks up the pace to look fast. I am confused by the performance push of the Ultraboost given the extensive Adizero line up. I understand the Ultraboost 5X may be more fashionable, but the cheaper Boston and even Adizero SL series may be better options for true performance. Regardless, the Ultraboost 5X is continuing to progress forward in some ways but really needs to permanently drop any posterior heel flare to truly get where it needs to be.
GRADES
Matt
Fit: A- (Comfortable knit upper with sock-like fit and a split heel design for those with heel sensitivities)
Performance: B+ (Snappy midsole that does best during uptempo efforts but a large heel flare makes the rearfoot clunky)
Stability: B [Neutral] (Solid sidewalls and external heel counter keep the foot centered but are offset by the large posterior flare that causes a medial push).
Value: B (Durable shoe that also looks good but only good for those who land a little farther forward. Otherwise should check out the Adizero Boston or SL series)
Personal: C+/B- (The posterior heel flare ruins this shoe for me except for uptempo efforts. I personally prefer the cheaper and faster Boston 12)
Overall Design: B
SHOP | SUPPORT DORAdidas Ultraboost 5XPrice: $179.95 at Running Warehouse
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FURTHER READING
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An update to the performance training companion to their super shoe
Find all Shoe Reviews at Doctors of Running here.
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