Ultraboost 21 Review: Is It Worth the Hype?

Despite being one of the world leaders in athletic apparel, one of Adidas’ flagship products, sometimes dubbed as “the shoe that saved Adidas,” is best known as a lifestyle product instead of a running shoe.

We are talking about the world-famous Ultraboost.

It is truly one of the most controversial running shoes on the market, with a healthy selection of 1-star, 5-star, and everything-in-between ratings for a variety of reasons.

Speaking from personal experience, my college athletic department had a contract with Adidas. We were given samples of the Supernova, Ozweego, and Adizero as our cross-trainers–but never the Ultraboost.

So is the Ultraboost 21 a bad running shoe?

Not necessarily.

It introduced Adidas’ TPU midsole technology to the mainstream, providing runners with optimal comfort, yet impressive responsiveness, for a training shoe.

Yet, it is far too heavy for most runners who are looking to up the pace, and Adidas’ constant tinkering with the features leaves many runners feeling like it lacks identity as a training solution.

But if you are looking to log some easy miles early in the morning and look stylish at brunch, then this could easily be the shoe for you.

Keep reading to find out everything you need to know about the Ultraboost 21 review!  

Adidas Ultraboost 21 Overview

Although there are a few sneakers that could make the claim, the Ultraboost 21 is arguably the best example of a running shoe that provides a crossover between performance apparel and casualwear.

Many serious runners feel like the shoe is simply too heavy for anything other than the most casual, laid-back jogging sessions. 

However, the Ultraboost franchise remains Adidas’ most popular sneaker line largely because of its crossover appeal. The techy midsoles and cosmic designs have made the Ultraboost a must-have sneaker for fashionistas ever since Kanye West wore the Ultraboost on stage.

With this in mind, you are likely to find the reviews for the Ultraboost 21 to be all over the place. It will be panned by some runners who feel like the shoe is just a gimmick that has released so many iterations simply as a money grab, saying that there is no way it is worth the money.

On the other hand, there will be the hardcore Ultraboost aficionados who think that the 21’s even more prominent heel stack and sock-like upper put it at the cutting edge of comfort, style, and performance.

In reality, the truth about the Ultraboost 21 likely falls somewhere in between. While the shoe will never be mistaken as the top everyday trainer for serious runners, it does have some beneficial features that make it far more than just a casual street shoe.


  • Adidas’ proprietary BOOST midsole technology, made from expanded thermoplastic polyurethane (eTPU) for top-flight comfort and responsiveness
  • Adidas Primeknit upper for a comfortable, sock-like fit
  • Midfoot cage and heel counter for support
  • Continental rubber outsole for improved traction and durability over earlier models
  • Stretchweb outsole technology enhances Continental rubber experience for a more energized ride
  • Midfoot cage and heel counter fabricated with Primeblue, a high performance plastic material that is made partially from recycled ocean plastic
  • One of the most modern, aesthetically pleasing designs in the performance sneaker game

Despite all of these positives with the Ultraboost 21, they do have to be taken with a grain of salt. It is far from a value shoe, and the unprecedented popularity of the Ultraboost line can easily fool the uniformed shopper into believing it is the premier running shoe on the market.


  • Exceptionally high price point
  • Larger sizes run close to 12 oz, making it one of the heaviest trainers on the market
  • Some runners heel like the heel counter does not work and contributes to blisters when running anything over 2 miles
  • The platform appearance of the heel stack is mostly that–appearance–and the functional section of the heel stack measures slightly less than the 30.5mm advertised
  • The toe box runs tight and shallow, further contributing to blisters

So now that you’ve gotten a summary of the strengths and weaknesses of the Ultraboost 21, let’s really dive in and see how the shoe performs along specific points.

Ultraboost 21 Review


Early versions of the Ultraboost did not fare well for durability. In fact, some runners felt that the shoe “melted like butter.”

Adidas heard this criticism and took the necessary steps to upgrade, teaming with Continental to fortify the outsole with industry-leading rubber to increase traction, ensure safe contact with the ground, and guarantee durability. 

In addition, the TPU midsole retains its comfort and responsiveness in the face of hundreds of thousands of foot strikes.

Finally, the Primeknit upper, while soft and sock-like, is thick and stretchy enough to keep pace with the durability of the shoe’s sole engineering.

All in all, runners should have no trouble surpassing 500 miles in the Ultraboost 21.


Few runners are completely satisfied with the way the Ultraboost fits.

As mentioned, some runners feel like the heel locking system does not really work, noting some pretty significant heel slippage when upping the intensity.

There are also numerous complaints of tightness throughout the toe box and midfoot, which is really magnified in people with wide feet.

To top it off, there is the issue of the 12 oz weight. Most runners find this cumbersome and liken it to running with ankle weights.

So when you combine all of these factors, it is definitely understandable why some serious runners find the Ultraboost 21 to have little utility other than as a lifestyle shoe for casual purposes. 


As a running shoe, the Ultraboost 21 is probably best classified as a high-cushion product.

After all, it is the product line that really launched Adidas’ BOOST TPU midsole technology to superstardom.

And while there are now many other running shoe brands that use TPU for their midsoles, it does not detract from the fact that the Ultraboost 21 offers outstanding cushioning. 

Through their TPU BOOST engineering, Adidas midsoles are designed to form closed cells around tiny pockets of air. This makes it feel like you are running on tiny, precision-engineered clouds.   

The one note of caution is that the enormous heel stack of the Ultraboost 21 is not completely BOOST cushioning. The sidewalls have an exaggerated raise to form a cup around the foot, giving the shoe the appearance of having a stack much greater than the advertised height of 30.5mm.

In fact, the actual midsole stack of the rearfoot measures between 30 and 31mm–impressive but not industry-leading. 


The Ultraboost 21 is not a stability shoe. It is not engineered with any features specifically designed to offer overpronation support and is best thought of as a neutral shoe for people with mid to high arches.

However, whether or not the shoe actually provides stability to the runner is a hot topic of debate in the running community. 

Some runners feel like the cupping action of the heel counter and newly unveiled Torsion shank in the outsole keep the foot locked in place during stride transitions and enhance structure, control, and stability. The 10mm heel-to-toe drop is also viewed as beneficial for alleviating stress off of the Achilles and posterior ankle areas. 

As mentioned, though, there is some debate as to how well these features work, with some users feeling like that the heel lock not only fails to lock the heel, but actually detracts from the Ultraboost 21’s position as a leader in the high-cushion sector. 


Despite the myriad issues with the fit, most runners feel that in terms of actual sizing dimensions, the Ultraboost 21 runs mostly true to size. If anything, it may run slightly larger than normal, so there may not be the need to size up like you would normally do when choosing a running shoe.

The one exception would be for runners with wide feet. Due to the aforementioned issues of cramping in the toe box, those with wide feet will likely need to go .5 sizes up.


One of the most pervasive critiques of the Ultraboost 21 is the cost. It is a pricey shoe, with most runners feeling that it is about $30 more expensive than comparable–if not better–highly cushioned trainers.

For better or worse, that is the price you will have to pay for wearing a shoe that has a bit of an iconic status in popular culture. 

Adidas Ultraboost 21 Design Features

Ultraboost 21 Review

Now that you have a strong understanding of how the Ultraboost performs in action, let’s take a look at this shoe’s anatomy.


We’ve seen that the upper provides the runner with a comfortable, sock-like experience while being thick and stretchy enough to offer the necessary durability for a daily trainer. 

This is a direct result of Adidas Primeknit technology. 

Using digital engineering to knit the entire upper in a single piece, the finely tuned yarn creates an elastic experience that essentially wraps around the runner’s foot. 

At only 1.9mm thick, the Ultraboost 21’s upper is extraordinarily lightweight and breathable. 


The eTPU midsole technology in the Ultraboost 21 offers the same legendary comfort for which Adidas BOOST technology is famous. In fact, the company says that the Ultraboost 21 actually uses 6% more BOOST foam than its predecessor, the Ultraboost 20.

There are five primary components that BOOST midsoles are known for:

  • Comfort
  • Adaptability to weather
  • Durability
  • Flexibility
  • Energy return

These characteristics combine to give the midsole of the Ultraboost 21 a unique blend of comfort and responsiveness. 

However, some runners feel like these qualities aren’t worth the slightly heavier weight in comparison to newer midsole solutions such as Lightstrike and Lightstrike Pro. 


The Ultraboost 21 adds a plastic Torsion shank in the outsole that extends across the midfoot. Adidas says that this Linear Energy Push (LEP) feature is added to increase durability and gives the shoe 15% greater propulsion than previous versions.

The benefits of the LEP outsole are debatable, as many runners feel that it is a bit superfluous in a shoe best suited for comfort over performance. 

The plastic shank is surrounded by a healthy amount of Continental rubber in both the forefoot and rearfoot, giving this shoe traction and durability on all types of running surfaces.

Alternatives to Adidas Ultraboost 21

Of all the running shoe lines on the market, the Ultraboost series generates one of the highest rates of online literature providing alternatives. This is because most runners feel like there are other ways to get the benefits of the Ultraboost at a lower price.

So to contribute to this trend, we’ve made a short list of shoes that stack up favorably to the Ultraboost 21

Saucony Freedom 3

The same TPU midsole technology found in the Ultraboost 21 is used in the PWRRUN+ midsole found in the Saucony Freedom 3.

So if you are looking for a cushioned, yet responsive, running experience, you will likely notice little to know difference between the two sneakers.

The Freedom 3 offers a more plush foam-mesh upper than the Ultraboost 21’s sock-like experience, yet weighs about 3 oz less than the Adidas product.

The lack of drop in the Freedom 3 may be a dealbreaker for some, though, as the 4mm figure is conspicuously less than the Ultraboost 21’s sizable 10mm mark. 

Brooks Ghost 12

If you are wanting a similar–and possibly better–running experience at a much more palatable price point, the Brooks Ghost 12 stacks up favorably to the Ultraboost 21.

Despite being considerably lighter than the Ultraboost 21, the BioMoGo DNA and DNA Loft midsole of the Ghost 12 give it comfort and responsiveness to rival that of the Ultraboost 21.

And while it may never be able to match the Ultraboost 21 in terms of style, it does come in 29 different color selections, providing plenty of options for fashion-forward runners.

Skechers GoRun 7+

Although the Skechers GoRun 7+ uses EVA midsole technology–what many runners consider to be “outdated” compared to TPU–its proprietary HyperBurst features give it energy return to match the Ultraboost 21, if not quite the same comfort level.

With a rockered sole and design that is ⅔ lighter than the Ultraboost 21, even a non-mainstream running name like Skechers can help you knock out some easy miles similarly to the more hyped-up Adidas product. 

FAQs About the Adidas Ultraboost 21 Review

A selection of the most commonly asked questions about the Ultraboost 21.

Is the Ultraboost 21 Actually a Running Shoe?

Yes, the Ultraboost 21 is actually a running shoe. (We wouldn’t be reviewing it if it weren’t!).

Although the Ultraboost line has attained a bit of an iconic status as a casualwear option–similar to Jordans in the world of gym shoes–it still has a multitude of features that make it great for hitting the track, such as the BOOST midsole, Continental rubber outsole, and plastic outsole shank for improved responsiveness.

What Kinds of Runs Is the Ultraboost 21 Best For?

The Ultraboost 21 is best for slower-paced, straight-line runs. 

It is too heavy to achieve optimal speed performances, and its ample midsole makes it better for runners looking to log some laid-back miles.

Is the Ultraboost 21 the Best Running Shoe by Adidas?

Although the Ultraboost line may be the most famous running shoe produced by Adidas, it is hard to say that it is the “best.”

There is actually a newer Ultraboost 22, released in December 2021, that offers an even more contemporary take on the classic Ultraboost line.

In addition, Adidas has other products, such as the Adizero series, that uses a more contemporary Lightstrike Pro midsole technology, which some runners feel make it a better product for long-distance runs than the Ultraboost.

In Summary – Adidas Ultraboost 21 Review

The Ultraboost 21 is truly a polarizing shoe.

Equal parts lifestyle product for everyday casualwear and high-cushioned running shoe for logging some easy miles, the Ultraboost 21 has its share of harsh critics and staunch supporters.

From our vantage point, if you are looking for a stylish shoe to wear on a day-to-day basis that can hold its own for basic running purposes, then the Ultraboost 21 should be at the top of your list. If you are looking for something a little more performance-minded, then check out one of our other reviews for other options that will provide a little more get-up-and-go!

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Tucker Lane

Tucker Lane is a freelance content creator. He is a former Academic All-American wrestler at the University of Nebraska. Following his competitive career, he coached at The Citadel for three years, followed by another three-year stint at the University of Northern Colorado. Upon retirement from wrestling, Tucker has adopted running as way to fill his passion for competition and exercise.

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