Yahoo Sport 
The adidas ultraboost 21 is a reliable partner for long, slow runs
Weight 340g (M) 297g (W)
Heel-To-Toe-Drop: 10mm
Type: road
Price: £160
RW summary
For long, slow runs this will be a reliable partner mile after mile.
It’s clear from the weight alone that this is not a shoe designed for anything but long, steady runs. But the heft and cushioning were among the best things about this shoe. Adidas likes to play with the Ultraboost despite the fact that it’s a bit of a cash cow for them. They’re never satisfied and each iteration is a little different from the previous one. This latest version features a chunkier midsole, a new torsion control device and an adapted upper
More Bounce Per Ounce
Adidas has added 6% more of their fabled Boost midsole foam to give extra bounce. Whether or not it achieved this aim is difficult to say. Nobody who was familiar with previous versions could day that they felt the difference. All they were able to state was that, this is a shoe that certainly feels extremely cushioned, and shock absorption was excellent. Even heavier runners, who normally get on better with a firmer shoe, enjoyed the experience.
Could be more responsive
The downside to all that mattress-like foam underfoot is that the UB21 has a little trouble going with you when you want to change speed. There was no sense of pick-up from the shoe on tempo or interval sessions. Ten years ago this wouldn’t even have been a talking point but with brands attempting to make their headline shoes all things to all people these days, that has to be marked down as a slight disappointment.
Twist no shout
There’s a plastic insert underneath the midsole called LEP (‘Linear Energy Push’) designed to give 15% more torsional rigidity – essentially to provide a stiffer ride and help you pick up the pace when needed. While the shoe seems to have failed in this last endeavour it still serves a purpose as we think this little device is why heavier runners were able to use the shoe, with it giving them the firmness and reassurance that they needed upon landing
Green is the way forward
A very encouraging aspect of the shoe is the positive remarks about the construction of the Primeknit upper, which is made from recycled ocean plastic as part of its long-standing partnership with Parley ocean plastics. Several testers who had not tried a shoe with any significant eco-credentials previously remarked that they had had some trepidation about trying it, assuming this would somehow feel scratchy, hot, or display some other technical failure as the downside of being environmentally friendly. No such experiences were had and the upper did its job extremely well (although narrow footed runners may find the overall shape just a tad wide for them). The important point here is that brands will be encouraged to continue exploring planet-friendly methods of production of they’re not getting pushback from consumers. As things stand currently we think that, while runners will be more than happy to look at greener footwear and apparel options – they’ll only do so if it does not compromise their experience in any way.
Conclusion
For the majority, this is a thoroughly traditional (if modern looking) long run shoe with oodles of bounce and comfort.
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