Adizero Prime X 2 vs Alphafly 3

The Adizero Prime X 2 is adidas going deliberately over the top. It is a supermaximal carbon running shoe with a stack so tall it sits above the World Athletics limit, which means it is not legal for record-eligible racing. That is the whole point. Freed from the rules, adidas piled on Lightstrike Pro foam and a set of carbon EnergyRods to build a long-run and marathon-training shoe that returns huge energy with almost no legs cost. You feel launched forward once you are up to pace. At 285g it is heavy for a carbon shoe, and the ride is more cruise missile than nimble racer. If you want a legal marathon racer, the Adios Pro 4 is the sibling to buy. If you want the most protective, most propulsive daily and long-run tool adidas makes, and you do not care about race legality, this is it.

Most carbon marathon shoes want strong, well-trained legs before they give much back. The Alphafly 3 asks for less than its looks suggest, and that came through in almost every review we read. Nike made the midsole one continuous piece for this version (the Alphafly 2 had a big gap under the midfoot) and took a lot of weight out. Reviewers describe a smoother roll from landing to toe-off, and it no longer feels clumsy on a warm-up jog. Ben Parkes, who has raced marathons in it, reckons it isn't so aggressive that only elites benefit, and thinks plenty of intermediate marathoners will get a lot from it.

It's still a specialist carbon racing shoe, and at £285 RRP it sits near the top of the market. It's also loud on the road, and some feet find it snug. For 5K and 10K races the lighter, snappier Vaporfly 3 makes more sense. For the half and the full marathon, we'd still put the Alphafly 3 near the front of the queue.