Adidas Ultraboost 21 Review

Comfort is the highlight with the Adidas Ultraboost 21, with one of the most comfortable uppers we have ever tested. A thick outsole provides ample cushioning but is firm and responsive when faster turnover is needed. The locked-in feel of the upper makes this model feel stable and supportive. Unfortunately, these features come at a cost at a higher weight of 12.9 ounces in a men's size 9.5, making this model feel a bit sluggish at times.

Performance Comparison

Premium upper comfort and great heel-to-toe rocker.

Photo: Matthew Richardson

Cushioning and Landing Comfort

The Adidas Ultraboost 21 has excellent landing comfort with its thick, durable outsole. The rockered design of the shoe helps roll your foot into a nice toe-off position, even if you land further back than your midfoot. This is helpful when fatigue starts to set in, and your form starts to break down. The rockered design also is beneficial when descending because of the added support of the heel, which takes off the stress from your Achilles and lower legs. The cushioning feels supportive and responsive, without feeling like too much energy is being put into the foam.

An enlarged heel helps absorb any discomfort from heavy landings.

Photo: Matthew Richardson

Landing comfort feels precise and planted, which is enabled by the extremely comfortable upper and natural position it puts your foot in. The under forefoot foam is slimmer, and the 10-millimeter heel-to-toe drop helps bring your entire foot in contact with the ground, increasing the landing comfort. Those that desire responsive cushioning should take a look at this model, though some may find the platform to be a bit cumbersome if you are more of a forefoot striking runner.

Responsiveness

The thickness of the midsole foam reduces the responsiveness a bit compared to some of the other lighter-weight models. We were presently surprised that even with the heavier weight, the Ultraboost 21 actually does a pretty good job of transferring power. This is partially due to the density of the foam, which isn't as soft and spongy as some other models. The heavier weight reduces the feeling of quickness and agility, but once you are planted, the firm platform helps propel you forward.

Thinner forefoot foam is responsive and offers a springy rebound.

Adidas does a good job of putting most of the cushioning under the midfoot and heel, leaving the forefoot to have the ability to really transfer power. If you don't mind sacrificing a bit of weight, we think the blend of cushioning and responsiveness is suitable and won't slow you down.

Upper Comfort

The upper comfort of this model is premium and comfortable. The tight-knit elastic fabric both hugs the foot and breaths extremely well. The outer wrap helps hold your midfoot in place while the upper conforms to your foot. Some users may find the toe box a little on the smaller side but should find a perfect performance fit due to the fabric's stretchiness.

The premium one-piece upper on the Adidas Ultraboost is among the best we've tested.

Photo: Matthew Richardson

The tongue is integrated into the upper for one seamless piece of fabric, which is unlike any of the other models we tested. The heel cup is supported by two plastic pieces which lock in the fabric and add rigidity through the heel. This is the standout feature of the Ultraboost 21, and we expect to see more upper designs like this in the future.

Lateral Stability and Support

The Ultraboost scores well for its support and stability that is partially due to the well-fitting upper. The shoe feels planted and stable without feeling too rigid, and with the moderate arch support, it should feel solid and predictable to most users. The forefoot is flat and allows for a natural footstrike which is supported by the 10-millimeter heel drop. On uneven terrain, it may feel a little less stable due to its higher stack height.

High amounts of support and stability make this a favorite for longer runs.

Photo: Matthew Richardson

Weight

The major downside of the Ultraboost 21 is the weight. At times the model feels sluggish, especially at the start of a run when you are feeling fresh. Luckily this model is durable and provides a lot of features for the added weight. The added enlarged heel ramp of the outsole provides a great platform that could help those that heel strike or need increased help getting into the toe-off position. Unfortunately, at this shoes' list price, we wish these features could come in at a lower weight.

Unique outsole material worked well and looks cool.

Photo: Matthew Richardson

Value

At the high end of the price spectrum, you are paying for maximum comfort and premium materials. We wish that these features came in a lighter weight package, and if they did, this model would be higher on our list. Unfortunately for us, the price-to-weight ratio puts this further behind in our standings.

Conclusion

If you are looking for premium comfort, then consider this model. With the comfort comes a great responsive platform, and the subtle cushioning will leave you thankful for when the runs become longer. We wish this model came in a lighter weight, but with durable materials and great support, we can see why this is one of the heavier models we tested. If you can make the price tag work, we would highly suggest this model for its all-around comfort. While pricey, this is one of the most unique designs we tested, and there are lots of colorways for you to choose from.

Top-of-the-line comfort and materials make this a joy to run in.

Photo: Matthew Richardson