Adidas Ultraboost 21 running shoe review: Does its performance live up to its looks?

First, the Boost – the midsole foam known as eTPU that provides a great cushioning and energy return. A mere six per cent more Boost capsules may sound marginal but when the existing technology was already so effective, a little extra packed into the new-look curved heel is a bonus. It gives the same combination of supreme comfort and bounce that fans of the Ultraboost have come to love. You can feel it even when you’re walking and we’d happily walk for miles in this shoe.

Next, the LEP. This is a “torsion system with stiffer, reinforced material in the midsole to provide runners with less flex in the forefoot and increased responsiveness” – and claims to add a 15 per cent increase in forefoot bending stiffness. You can feel this if you try to manually bend the shoe compared with last year’s model. 

It certainly gives a springier ping off the forefoot while running, but still maintains a nice roll-through from heel to toe, aided by its slight rocker shape, and it has a sensitive ground feel under the forefoot for such a cushioned shoe. It has superb arch support that you can feel coming up to meet you on every step and the outsole grips well in the wet.

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With a tongue-free, sock-like construction, the Primeknit+ upper clings snugly around the mid-foot, although the fit is very wide in the forefoot. While that allows for a nice spreading of the toes on landing, you might find yours wallowing a bit if you have narrow feet. 

The lacing system runs through the plastic cage on either side of the upper – it locks the foot in tightly to a supportive heel counter and the shoe stays put beautifully throughout a run. Our only gripe is that the laces don’t flow easily through the cage, making them hard to loosen at the end of a run.

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Half of the upper is textile and 75 per cent of that is made from Primeblue yarn, a recycled material made in part with Parley Ocean Plastic and no virgin polyester is used. Like the majority of trainer brands, adidas could do even more towards increasing sustainability and creating recyclable products, but it’s certainly a positive.

At 340g, the 21 is slightly heavier than its already heavy predecessor. Not by a lot but we’re surprised that the brand hasn’t tried to reduce its weight as it slightly detracts from the increase in responsiveness created by the LEP. It means that we’d use it for steady, shorter runs or recovery runs so that the plush cushioning can give weary legs a rest but it wouldn’t be our first choice for long distances or speedy training runs.