Adidas Adizero Prime X Strung review: Fast and efficient Nike Alphafly 2 rivals

We’ve put in some big, lung-busting miles to bring you this Adidas Adizero Prime X review. And rightly so. Adidas has kicked out some impressively propulsive race shoes in recent years – the Adios Pro 3, the original Prime X and the Takumi Sen 8. But they’ve not always been the most comfortable.

So when we heard Adidas had fused its clever, cutting-edge Strung uppers to its punchy Prime X midsole, we had high hopes for a carbon shoe to rival the Nike Alphafly Next% 2, without those comfort concerns. That’s why we’ve raced marathons, chased mile PBs and blown our lungs on all-out 5kms to see if this the fastest – and comfiest race – shoe on the rack? Can the Adidas Prime X Strung topple the Nike Alphafly? Read on to find out.

Adidas Adizero Prime X Strung review: Price and availability

The Adidas Prime X Strung was launched in September 2022. It’s available to buy now at Adidas US, Adidas UK and Adidas AU for a recommended retail price of $300/£230/AU$420. That’s £40 cheaper than the Nike Alphafly Next% 2 in the UK (but oddly $25 more expensive in the US). It’s £10 pricier than the Adidas Adios Pro 3 in the UK, though again, runners in the US get stung an extra $50 for the Strung. Other rivals to consider in the carbon running shoes race include the new Saucony Endorphin Elite ($275/£280), the Saucony Endorphin Pro 3 ($225/£210) and the ASICS Metaspeed Sky+ ($250/£225). 

Adidas Adizero Prime X Strung review: What’s new? 

The Adidas Adizero Prime X Strung is the first shoe in Adidas’s Adizero pacier race collection to feature the innovative Strung uppers. First released as part of an Adidas Futurecraft project, the Strung textile technology makes it possible to place fibres and dictate their properties, thread by thread, based on athlete data. In theory, that should mean a step up on regular uppers. The result is a breathable and flexible upper without heavy overlays that hugs the foot with a race feel. But crucially doesn’t pinch or constrict. 

But that’s not all the Prime X Strung offers. Those clever Strung uppers are fused to the same midsole unit that you’ll find in the original Adidas Adizero Prime X. There’s a big three-layer stack of Adidas’ lightest and most responsive foam, the Lightstrike Pro, which is sadly not race-legal on this occasion due to the extremely high heels (49.5mm heel / 41mm forefoot).

The 8.5mm drop midsole wraps an aggressive rocker shaping around a set of carbon energy rods that sit underneath the metatarsals to provide lightweight stiffness and limit energy loss at toe-off. The rods' design also aims to help the foot flex naturally. The outsole has a thin covering of protective and grip-enhancing Continental rubber under the forefoot, and smaller reinforced sections on the high-impact heel areas.

Unlike the Nike Alphafly’s booty uppers, the Prime X Strung have a traditional lace set-up, with a thin, flat minimal foot wrapping tongue that’s stitched in on one side. There’s minimal padding to the flexible heel collar, which also has a foldable tab to help you pull the shoes on. That can be tucked down to avoid any heel rubbing.

Adidas Adizero Prime X Strung review: Fit

When it comes to fit, I ran in my regular size, UK 8.5. I found it easy to get a comfortable fit with reliable lace lockdown and good heel hold. I sometimes struggle with Adidas shoes coming up narrow, but the Prime X Strung ran perfectly well, and I’d recommend going true to size. 

The Strung uppers make step-in comfort infinitely better than the Adidas Adios Pro 3. They feel light with a natural, disappearing feel on your foot and give your foot a race-feel hug without restriction. 

The Strung’s more traditional laces and tongue set-up also make them considerably easier to get on than the Alphafly’s tighter booty fit – a real bonus if you have wide feet or a high in-step. 

There’s plenty of room in the Prime X Strung toe box, too. But perhaps more importantly, if – like me – you suffered with pinch points across the top of the midfoot, on the big toe knuckle, in the Adidas Adios Pro 3, there’s none of that here. 

Adidas Adizero Prime X Strung review: Running performance

I’ve run more than 150 miles in the Adidas Prime X Strung including racing a full marathon, two half marathons, and some all-out 5km and mile time trials. Most of those miles were on roads and pavements with the occasional stretch of compacted gravel river paths. I ran in some pretty wild and wet conditions, too.

The TLDR: A cracking carbon racer to rival the Nike Alphafly Next%2, these are everything you want in a speed shoe. Light, snappy and responsive across any distance from the mile to the marathon, they’re at their best when you’re running with all-out intent and locked-in good form.

The Prime X Strung are designed primarily for marathon racing, and I found them a joy over the 26.2 / 42km. These are shoes you feel like running fast in the moment you lace them on, and they excelled over the half marathon distance, too.

Once you’re moving, that combination of the carbon rods, the foam and the rocker produce pronounced propulsion, spring, roll and efficiency. The big stack of Lightstrike Pro foam also definitely helped my tired legs stay fresher deeper into my marathon as well.

The marathon test was on a torrentially rainy day with a route that was mainly road but had some mud paths. That proved to be an excellent test for the grip, which held up really well. As did the Strung uppers. The shoes took on water but didn’t hold it, so they never felt heavy.  

In testing, I also ran my second fastest mile ever in the Prime X Strung on a 400m park loop. The only shoe I’ve run quicker in is the Alphafly. So they can cope nicely over shorter distances, too. 

However, one word of warning: they struggle with stability in tighter corners. I found my foot sliding off that springy midsole platform on sharp turns. I often spent the next few strides realigning my foot in the shoe. So they may not be the best choice for twistier, turnier races. 

There’s also the question of the stack height, which isn’t race-legal. But we’ll leave you to decide whether you think it’s ok for non-elite runners to race in 50mm stack shoes. 

Adidas Adizero Prime X Strung review: Durability

After at least 150 miles, the Adidas Prime X Strung isn’t showing any worrying signs of wear to the outsole or the Lightstrike Pro midsole. I had some concerns about the lace eyelets breaking off but nothing to report here, either. Even the flexible heels – without any substantial plastic heel counter – are still in great shape. This is a shoe I’d expect to use for 300+ miles, at least.

Adidas Adizero Prime X Strung review: Verdict

This is a fantastic carbon race shoe that really comes alive when you’re running at your best, going all out, in your best running form and chasing fast finish times. The Strung uppers are a fantastic improvement, bringing superior comfort over Adidas’ other carbon race shoes. The ride is punchy, powerful and efficient but best of all – it’s fun on any distance. With as much punch as the Nike Alphafly Next% 2, better comfort than the Adidas Adios Pro 3 and much cheaper than the Saucony Endorphin Elite, the Adidas Prime X Strung is right up there with the best. 

Adidas Adizero Prime X Strung review: Also consider

The Prime X Strung is right up there with the best carbon race shoes on the shelves right now. The other shoe we’d recommend you look at first is the Nike Alphafly 2. This shoe remains one of the best, most responsive race shoes going – particularly for distances like the half and full marathon. If you prefer a booty fit, go for these. 

If you want something cheaper, more stable and more generally comfortable across a wider range of paces, the Endorphin Pro 3 is another excellent race shoe. It’s probably a touch more protective over longer miles than the Prime X Strung, though not quite as punchy. But that trade-off also means it works well for faster training sessions as well as chasing PBs. Worth considering if you value that versatility. 

Another newcomer to the carbon shootout, the Saucony Endorphin Elite is a capable carbon racer that balances propulsion, energy and response with a touch more stability than some carbon shoes. Livelier than the Endorphin Pro 3, there’s a lot to like in this marathon-friendly option. However, the price tag is a little large for our liking. And we’d recommend the Prime X Strung more highly.