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Adidas UltraBoost 21

Adidas UltraBoost 21 Review Analysis (2021)

Last update: March 2024

Half sneaker, half running shoe, the Adidas UltraBoost 21 is a sleek and comfortable option for your daily runs.

The Consensus

8.5Overall score
Stylish and comfortable running shoe but too heavy and not responsive enough
The Adidas UltraBoost is much anticipated every year but eventually leads to plenty of mixed reviews. The UB21 is no exception and proposes the same formula: a model halfway between a sneaker and a running shoe that tries to combine style and performance.

The sleek design is an achievement on its own and will please runners who like good-looking shoes on their feet. The Primeknit upper and its bootie conception offer great comfort and impeccable foot lockdown, according to the testers. It’s both breathable and stretchy for a precise and adaptive fit. Also, the Primeblue material uses 50% of recycled plastic from the oceans. The UB21 also marks the midfoot plastic cage’s return that many runners decried in the past on previous versions. However, luckily it’s barely noticeable this time.

Then, the cushioning shifts gear with a heel stack height of 31 mm instead of 27 mm the year before. Adidas announces 6% more Boost, and it shows: the small white TPU granules give a massive sole, especially in the heel area. Another significant change, the Linear Energy Push plastic plate, replaces the Torsion System of the previous models. It gives structure to the platform for better stability and a snappier toe-off. However, in practice, testers found the cushioning firm and clunky, with little bounce, although the shoe provides a stable ride. The weight doesn’t help with 12.3 oz (348 g) (even more than the previous model), limiting its speed ambitions.

Finally, the outsole also boasts a new design and succumbs to the exposed foam trend (only in the center) without limiting durability or grip, both of which are very good.

In summary, unless you’re a fan of the UltraBoost collection, there’s little reason to opt for the UB21 other than its comfortable lockdown, good shock absorption, and sleek design. Otherwise, the Ultraboost is too heavy and too stiff for an enjoyable ride, even for daily runs.
Comfort
8.5
Durability
9
Value for money
7.5
Design
9
PROS
  • Great knit upper that offers impeccable lockdown
  • Good shock absorption
  • Stable run
  • Durable and grippy outsole
CONS
  • Heavyweight
  • Expensive shoe
  • Firm cushioning that lacks responsiveness

Technologies

Outsole

  • The outsole of the Adidas Ultra Boost 21 uses Stretchweb Continental: a resistant rubber with a unique tread pattern to optimize durability and traction on city surfaces.
Adidas UltraBoost 21 continental rubber outsole

Midsole

  • Boost equips this new UB model. Adidas’s leading midsole technology consists of thousands of little balls in thermoplastic polyurethane fused to absorb shocks and improve the bounce.
  • Also, the Linear Energy Push is a torsion system that increases the structure of the platform to maximize the energy return. According to Adidas, this technology improves forefoot rigidity by 15% for a snappier toe-off.
  • The removable insole improves the comfort inside the shoe and helps with regulating humidity.

Upper

  • The Adidas UltraBoost 21’s upper features Primeknit: a stretchy, lightweight, breathable, and smooth-looking engineered knit that comfortably wraps around the athlete’s foot for a fitted and comfortable foot lockdown.
  • Primeblue is an engineered textile composed of at least 50% of recycled Parley Ocean Plastic to reduce the carbon footprint of the shoe.
  • The bootie construction reduces irritations and makes it easy to put on and take off your shoes.
  • The external heel counter keeps the foot secured in the shoe to prevent slippage

Facts

Technical Specs

TerrainRoad
Pronation typeNeutral
Drop10 mm
Heel stack height31 mm
Forefoot stack height21 mm
FeaturesRecycled materials
Weight (men)348 g/12.3 oz
Weight (women)316 g/11.1 oz
Release year2021

Cushioning

Softness (1-5)2 – Firm
Bounce (1-5)2 – Low

Technologies

OutsoleStretchweb Continental
MidsoleBoost, Linear Energy Push, removable insole
UpperPrimeknit, Primeblue, bootie construction, external heel counter

Use

SpeedSlow, moderate
DistanceMid, long, 10k, half marathon
WorkoutDaily runs

Reference: Adidas’ official website

Comparisons – Adidas UltraBoost 21 vs.:

Adidas UltraBoost 20

The UB21 has more cushioning with its higher stack height featuring more BOOST. However, it makes it heavier, and it weighs 0.7 oz/20 g more than the UB20. For the rest, the cushioning is similar. Good to note: the UltraBoost 21 is less narrow, which was one of the main negative points of the previous model.

Frequently Asked Questions (FAQs)

Is this model true to size?

This shoe dropped just recently, and we don’t have enough feedback from runners yet to give a definite answer. We will update this section as soon as we have more information. However, overall, Adidas running shoes tend to fit true to size. In any case, if this is your first pair of Adidas, a trip to the store is always better.

I overpronate. Can I run in the Adidas UltraBoost 21?

Yes, this model should be suitable for everyone. Indeed, it’s a neutral running shoe. Therefore, it aims to suit all runners independently from their pronation type. It doesn’t have stability technologies to correct the stride and reduce overpronation. Anyway, let’s note that shoe models for overpronation are no more effective than neutral shoes to prevent injury. Accordingly, we advise that you choose your running shoes according to their comfort, the most critical criterion.

Is this shoe recommended if I’m a heavy athlete?

Yes, this model should be just fine as it has a generous stack height with 31 mm under the heel and 21 mm under the forefoot, which is sufficient for the vast majority of runners.

Is this model adapted to run a marathon?

Yes, this Adidas running shoe is very well suited for different workouts and distances. As far as the marathon is concerned, it depends above all on how you feel. If you can have multiple long training sessions (12 mi/20 km and beyond) without pain or discomfort, then it should be a good choice for your event.

Kevin Le Gall

Kevin Le Gall

Kevin is the founder and editor of Runner's Lab. He started running in 2015 and completed his first marathon in Rotterdam in 2016. He's also worked for Under Armour from 2016 to 2018 and helped launch their running collection in Europe (in particular the HOVR shoes). In addition, Kevin is a 300-hour certified yoga teacher (Sivananda) and uses this experience to run more mindfully with a focus on well-being over performance.

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