MIDSOLE

The best feature of the Adidas UltraBoost is the highly responsive and cushioned midsole. If you love a lot of extra bounce and plush step-in feel in your running shoes, this design will not disappoint. The Boost midsole is made from thermoplastic polyurethane particles.

Basically, the midsole is composed of closed-cell plastic particles that trap tiny pockets of air. When you run, these particles collapse and bounce back when not under pressure.

This provides runners with a light and bouncy ride that feels like running in tiny trampolines. Plus, the Ultraboost 21 offers 6 percent more bouncy particles than previous versions.

What runners also love about this midsole is that it includes an LEP torsion system. This torsion system consists of a small plate around the forefront of the foot that boosts agility and offers quick and springy toe-offs.

In application, the LEP torsion system act as a rocking chair for your feet that naturally propels you forward as you move through your gait cycle.

OUTSOLE

The outsole is composed of a blend of Adidas’ proprietary Continental rubber pods with the addition of Stretchweb materials that really ground you down to the earth. The Stretchweb materials are lightweight and insanely flexible and boost your overall agility.

It boasts a slightly tacky finish that really grips the ground under your feet, and excels on treadmills, pavement, and concrete. When running in grass or mud, runners found that this material can get a little slick.

By utilizing pods of their Continental rubber on key areas of the foot, the Adidas UltraBoost 21 remains lightweight and agile without sacrificing durability. It feels lightweight and flexible underfoot, but it is built for runners that clock well over 500 miles in their running shoes.

Runners found that even on slick sidewalks, this outsole really stuck to the ground. The Stretchweb materials along the outside of the foot offer a confident gait cycle on slippery sidewalks, but it underperforms when running in the grass.

As long as you stick to the gym or the sidewalks, you won’t run into any problems with the performance of this unique outsole.

UPPER

There are quite a few reasons to love the construction of the upper of this design. It is composed of Adidas’ Primegreen knit materials that are composed of 50 percent Parley Ocean Plastic. This plastic is found on coastlines before it reaches the ocean, and then shredded and used much in the same way as virgin plastic.

Buying new running shoes is essential but can become rather wasteful over the years (because you can only retire so many running shoes as lawnmowing shoes!), and Adidas’ recycled plastic upper is much kinder to the planet.

While you can feel good about the manufacturing process of the upper, it also performs quite well. The cage system sits nice and flush against your foot and doesn’t rub up against the top of your foot as you run.

Some runners felt that the UltraBoost 20 caused blisters on the top of their foot, and the UltraBoost 21 fixes those minor issues. This upper is lightweight and breathable, and it is made to move.

PERFORMANCE

Overall, I would recommend the Adidas UltraBoost 21 for neutral runners that love a good deal of cushioning and energy return.

The construction of the Boost midsole with the addition of the LED torsion systems helps to keep your gait cycle nice and bright. It’s a shoe that is made for neutral runners that love to conquer long distances while taking it easy on their joints.

Previous versions of this shoe were gear more toward long-distance runners, but the redesigned torsion system and the flexible outsole are also great choices for speed as well.

If you love switching up your workouts with the seasons, this is a shoe that is able to keep up with your varied workouts inside and outside of the gym.

The only downside to the performance of this shoe is that the outsole isn’t exactly designed for the grass or muddy conditions. When running on hard surfaces such as sidewalks, asphalt, or treadmills, the tacky nature of the outsole really grips the ground under your feet. Even on slick rain-soaked sidewalks, your stride remains nice and confident.

On grass, however, this shoe can become a little slick. It’s also important to note that the small grooves in the outsole love to pick up small rocks when running in rocky conditions or trailheads. It’s not a deal-breaker, but it is something worth noting.

FIT

There were very few complaints about the sizing of this shoe. It runs true to size, which means that if you are a size 10 in other Adidas running shoes, the same can be said for the UltraBoost 21.

If you have newer worn Adidas shoes before, fear not! They have compiled a very accurate sizing chart to ensure that you get the perfect size for your feet.

Adidas recommends taking detailed measurements of your feet at the end of the day (when they are the most swollen), and then compare those measurements to their detailed sizing chart.

This shoe is also a medium-volume shoe, which means that your feet will have plenty of room to move, and the unique cage and lacing systems help to craft that perfect locked-down fit.

If you find that these shoes just don’t fit you right. Adidas also offers a 30-day free exchange program with no questions asked.

Sometimes, a shoe may fit perfectly right out of the box, but changes in your feet as you run may not translate as well on the track.

If that happens, simply return the shoes within the 30-day window and exchange them for a smaller or larger size free of charge!

PRICE

The Adidas UltraBoost 21 is a fantastic daily running shoe that comes in at a fairly steep price point. It’s not the most expensive running shoe out there on the market, but it isn’t exactly considered to be budget-friendly.

While it may come in at a pretty steep price point, the added durability and performance features offered in this running shoe are well worth every penny. Its high-performance outsole is designed to perform just as well on mile 250 as it did on mile one.

If you feel that you can’t quite swing the higher price point of this running shoe, you can also purchase it through Adidas’ payment program. You have to option to make four smaller payments over the course of four months that are completely interest-free.

There have been a few keys changes made to the Adidas UltraBoost 21 that really makes it stand out. Overall, the performance between the Ultraboost 20 and Ultraboost 21 are very similar.

They both provide highly cushioned rides that are designed to give you a good deal of cushioning and energy feedback when running for long distances.

The UltraBoost 21, however, added a few extra bells and whistles that give it a slight edge over previous versions.

The biggest and most noteworthy addition to the UltraBoost 21 is the addition of the LEP torsion system. Under the midsole is a layer of LEP (or Linear Energy Push) that makes the midsole just a bit more flexible than previous versions.

While running, it almost has that same feel as the Hoka MetaRocker. It seamlessly guides your foot forward in a rocking motion that helps naturally propel your forward and allowing for higher agility in the forefoot.

Another great product we reviewed is the Adidas Solar Boost 4, so make sure to check it out as well.

Compared to the UltraBoost 20, the addition of the LEP makes this shoe feel less stiff without affecting the overall bounce from the highly cushioned midsole.

This midsole also boasts 6 percent more boost capsules that make this shoe just a little bit more comfortable and supportive when compared to previous versions of the UltraBoost.

This neutral daily trainer is a great choice for runners that love extra cushioning but don’t want to be slowed down. Often, highly cushioned running shoes have a tendency to be big and blocky and aren’t necessarily designed for agility work.

What makes the Adidas UltraBoost 21 unique is that it is packed with responsive energy-pumping features to keep your gait cycle nice and bright.

The most welcomed addition to this shoe is the LEP torsion system that keeps your gait cycle nice and bright. The midsole provides excellent cushioning that won’t weigh you down, and the Primegreen upper really contours to the shape of your foot to boost lockdown.

It may not be the most affordable running shoe out there on the market, but for runners that want something that offers explosive movements without hindering energy return and comfort, the Adidas UltraBoost 21 is well worth the investment!