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Hoka One One Carbon X Review

Carbon fiber plates are becoming more and more popular, particularly among road racing shoes.  The Nike Vaporfly series, the Hoka Evo Carbon Rocket, the New Balance Fuelcell 5280, the 361 Chaser 2 and unnamed Saucony and Brooks racing shoes are either on the market or have been seen on feet of elite runners.  Almost all of these shoes have been limited to marathon races and below.  Hoka One One is one of the first to market and create a carbon fiber based ultramarathon racing shoe.  The Carbon X, advertised on full blast at the Project Carbon X, was on the feet of Jim Wamsley as he broke the 50 mile road record.  This is a unique shoe and has been a blast to run in.  A shoe for both ultra distance racing and long runs, yet still fast enough for workouts and speed.

Hoka Carbon X
On Sale for $99 at Running Warehouse

Weight: 8.7 oz (men's size 9)
Stack Height: 32mm / 27 mm (forefoot / heel)
Drop: 5 mm
Classification: Ultramarathon Racing Shoe


The fit of the upper is fairly true to size, if a little long.  This is something I would expect from an ultramarathon shoe to accommodate swelling.  I typically wear a size 10 and my pair fit perfect.  While I do have a little extra length up front, it is not something I have noticed.  The width is on the medium size.  It is a little snugger that most traditional shoes throughout, but a little wider for a racing shoe.  The fit is fairly normal for a Hoka, except that there is more width in the forefoot.  The single layer engineered mesh does has some give to it but the most notable aspect is how fantastic the breathability is. 

Not a shoe that I would use during a harsh winter, but great for Southern  California as things start to heat up here.  The upper is extremely soft against the skin and could be worn sockless (although I would not over an Ultra).  The foot is locked down very well and the Carbon X is one of the few shoes I do not need to use a lace lock on (but still do).  There is an extremely small and flexible heel counter, but most of the heel is extremely flexible.  Most of the lock down comes from elevated midsole side walls around the heel.


The ride of the Hoka Carbon X is very unique.  Protective yet responsive is probably the best I can describe it.  The Carbon X has a firmer ride that feels consistent from heel to forefoot.  The metarocker combined with the carbon plate provides a smooth rockered transition no matter where you land.  The toe off is initially a little stiff thanks to the plate, but smooths more as the pace increases.  The Carbon X has a 5mm heel drop, but the rocker shape takes pressure off of the calves.


The Hoka Carbon X is one of the more stable Hoka shoes I have tried.  This is due to the the wider last (shape), particularly in the forefoot, the carbon plate and the elevated midsole side walls in the heel.  There is significant sole flare both medially and laterally at the forefoot that provides a very stable place to toe off from.  The carbon fiber plate is also designed to facilitate motion onto the great toe for a faster and more efficient toe off.  The elevated midsole side walls around the heel also do great job of locking in and stabilizing the heel during rearfoot landings.  The Carbon X has no form of posting or wedges and is not classified as a stability shoe.  However there are plenty of stabilizing features that most people will do fine in this shoe.


The combination of the carbon fiber plate, extra cushioning and rocker shape allow for a variety of workouts.  It is very rare that you can warm up, do an effective hard workout, then cool down all in the same shoe.  While the Carbon X can handle easy runs down to some track repeats, the shoe feels best during quicker long runs and tempo runs.  Similarly, those looking for extra cushioning could use this shoe for racing, but given the 8.7 oz weight (men's size 9), the Carbon X would work best for ultramarathon or marathon racing on the road. 


Thanks to the extensive cushioning and stiff carbon fiber plate, the ride of the Carbon X has remained exactly the same since my initial test run.  There is no additional durable rubber and the outsole is just exposed EVA.  Over the 55 miles I have used them, most of the outsole has remained in good shape, however there is some significant wear already at my usual spot in the posterior lateral heel.  I cannot feel this at all, but am concerned what this may look like 150-200 miles.  I do expect to get at least 250-300 miles out of these shoe, but most people will be able to get FAR more thanks to the set up of the midsole. 


Resupination is an extremely important part of gait.  Most discussions around footwear are focused more on the initial contact (landing) and midstance phases of gait.  This is due to most of the industry focusing on shock absorption (landing) and stability (midstance).  Often companies will ignore the forefoot as an important place of stability.   As a runner transitions into terminal stance and toe off, the foot and ankle need to do something called supination.

Image result for toe off running
Image from

Most people will be aware of pronation, where during landing, the medial arch of the foot lengthens (or collapses under control) in order to help absorb shock.  Pronation is a coupling of ankle eversion, dorsiflexion and abduction.   It is an extremely important motion that helps with absorbing impact.  As with all things in life, this does need to be controlled with good eccentric muscle strength.  For more on this topic, go to my Pronation Running Impairment Post.  When the foot pronates, it becomes a flexible shock absorbing mechanism.  When the runner moves into terminal stance to create a power push off, having a flexible base creates instability.  That is why the foot and ankle need to return to a supinated position, where the foot becomes rigid and stable.  Supination involves ankle inversion, plantarflexion (calf engagement, push off) and adduction.  It is very important as mentioned to create a stable base for the rest of the body to push off from.  Getting the foot into a supinated position is also incredibly important for proper utilization of the big toe (hallux) and the windlass mechanism of the foot (which is incredibly efficient and powerful when utilized correctly).  Lack of resupination can lead to lack of proper use of the big toe, which is a suspected mechanism in the development of hallux valgus (aka bunions).

Image from Runner's World Hoka Carbon X Video Review
Photo of the Carbon Plate in the Hoka Carbon X

There are three mechanisms in the Hoka Carbon X that facilitate all these mechanisms.  First, the metarocker/toe spring in the forefoot reproduce the flexibility needed at the great toe to allow for a smooth transitions.  Second, the flared forefoot outsole creates an already stable base for the foot to transition off of.  Finally, the carbon plate (see photo above) biases the foot toward a supinated position, creating a rigid lever underneath the big toe to facilitate a strong toe off.  These mechanisms work very well together, creating a smooth and strong toe off.  I applaud Hoka for the design of this shoe, particularly in the front of the foot.  These are excellent applications of biomechanics to facilitate the foot without traditional (and often archaic) methods of stability. 


The Hoka One One Carbon X is for those looking for an ultramarathon or cushioned marathon racer that easily doubles as a long run or long workout shoe.  For those that need a stable, firm ride with a little more cushioning, the Carbon X will fit your needs.  The Carbon X can handle a variety of paces, but is best for long runs, uptempo runs or ultramarathon racing on the roads.  Others will find this 8.7 oz shoe great as a lightweight trainer.  The Hoka Carbon X is a unique shoe that has a variety of uses and is well worth checking out. 


Our Youtube Channel Review of the Hoka Carbon X!  Please like and subscribe!


Fit/Upper          9/10
Ride/Midsole    9/10
Stability            9/10
Speed                8/10
Durability          810

Total Score: 86%

Thanks for reading!


Find the Carbon X, currently on sale at Running Warehouse for $99, here.
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Editor's Note: As always, the views presented on this website belong to myself or the selected few who contribute to these posts. This website should not and does not serve as a replacement for seeking medical care. If you are currently injured or concerned about an injury, please see your local running physical therapist. If you are in the Los Angeles area, I am currently taking clients for running evaluations.

Dr. Matthew Klein, PT DPT OCS FAAOMPT
Doctor of Physical Therapy
APU PhD Candidate: Rehabilitation and Movement Science
Board Certified Orthopedic Clinical Specialist
Fellow of the American Academy of Orthopedic Manual Physical Therapists

***Disclaimer: These shoes were provided free of charge as part of a Hoka One One Carbon X Marketing Event.  We thank the  people at Hoka One One for providing a pair for us.  This in no way affected the honesty of this review. We put at least 50-75 miles on trainers and 10-25 miles on racing flats prior to reviewing them. Currently I have 55 miles on my pair. My views are based on my extensive history in the footwear industry and years testing and developing footwear. If you are a footwear rep looking for footwear reviews or consultations on development, we are currently looking to partner with companies to assist, discuss and promote footwear models. Partnership will not affect the honesty of our reviews.

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