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Taking a closer look at running shoes’ bottom bits
The battle to produce the lightest, most efficient, most comfortable, most durable and ultimately fastest running shoes has been raging a long time. But more recently the focus of that fight has shifted firmly to the sole, with the biggest strides being made on the bottom half of your shoes. From Nike ZoomX foam to Adidas Boost, via Hoka One One’s CarbonX and ASICS MetaRide, right now it’s all about what’s under your foot as much as what’s around it.
In a bid to workout what’s what, we asked our gear expert, Kieran Alger, to to flip over the latest shoes from the biggest brands to see what their bottom bits bring to the run.
Nike Next%
The successor to the popular 4% – but actually a closer match to the Vaporfly Elite shoes used during the breaking2 project – Nike says the all-new ZoomX Vaporfly Next% is its ‘fastest ever running shoe’. On some athletes in some tests, they said, the combination of 15% more ZoomX foam, a carbon fibre plate and the lightweight uppers, increased efficiency by 5%.
And when Eliud Kipchoge wore them to win the London Marathon in 2019, plenty of people questioned whether the technology in the shoes is so good it actually represents ‘shoe doping’ – a kind of unfair advantage for those lucky enough to lace them up. And let’s face it at £239.99 and limited release, that’s not going to be many people.
The ZoomX foam is Nike’s proprietary compound made from Pebax – a type of high tech polymer that’s soft and springy and somehow returns some of the energy when your foot strikes the ground, transferring it into your toe off.
While ZoomX foam is one part of the sole mix, the real magic might actually be in the carbon fibre plate, and not necessarily in the way you might think. While it’s widely thought that the plate acts like a spring, adding track-spike-like propulsion during toe off, research has suggested that the plate actually brings stability to the ankle joint and reduces wasted energy, leading to overall efficiency gains.
In combination the ZoomX foam and the carbon fibre plate create a running sensation that feels noticeably like you’re being propelled forward. And with the world’s fastest marathon runner tearing up records in various versions of this tech-laden shoe, its little surprise that just like the 4%, the Next% technology is already in big demand.
Who benefits most: Forefoot striking speedsters searching for those percentage point gains that’ll push them under running’s biggest time barriers. And those with bigger bank balances.
ASICS MetaRide
Interestingly, it was another piece of research into potential efficiency gains around the ankle joint that also spurred ASICS designers into creating its groundbreaking shoe, the MetaRide.
Launched in March 2019, the MetaRide features a brand new curved sole design that physically lifts the toe off the floor so that when you lie them flat on the ground there’s clear air between the shoe and the tarmac at the the toes.
The sole is made up of a number of different components including ASICS proprietary Flyte EVA foams. In the heel there’s a considerable wedge of FlyteFoam Lyte (ASICS’ answer to Adidas Boost and Nike ZoomX) that works in conjunction with some rearfoot gel to cushion the initial heel impact.
Towards the front of the shoe you get Flytefoam Propel, a foam with a different density that’s there to assist with responsiveness and propulsion on toe-off. Sandwiched somewhere in between is a rocker plate that helps guide the foot through the whole motion from heel down to toe off, and that’s crucial to reducing the angle of the ankle and maximising efficiency in each foot strike. Together this is what ASICS calls it’s Guidesole technology. Crucially, this shoe isn’t designed to help you go faster, it’s about being more efficient, primarily if you’re a heel striker.
So does it work? Well according to ASICS research, done in conjunction with Progressive Sports Technologies based at Loughborough University, the Guidesole creates just short of a 20% reduction in energy loss around the ankle joint, which is significant.
“There’s no doubt it’s a very good shoe,” says Runner’s World Gear Editor Kerry McCarthy. “The logic behind the design is sound and it’s extremely comfortable. Personally I felt it made me run not only quicker but more easily.”
Read Kerry’s full ASICS MetaRide running review
At £225.00, you’ll pay for a premium for this technology – in fact it’s not much cheaper than the Nike ZoomX Vaporfly Next% – but as with Nike, we’d be very surprised if it didn’t make its way into cheaper shoes before very long.
Who benefits most: Heel-striking 4-7 hour marathon runners. Again, will suit those with deeper pockets.
Hoka One One CarbonX
While Nike’s sole technology has underpinned record-breaking runs at the marathon distance, Hoka One One’s has done the same for ultra. As part of its own #breaking2-style ultra Project Carbon X, Jim Walmsley recently broke a 35-year standing 50-mile world record, running a 4:50:08 (that’s the equivalent of 5:48 min/miles) in the Hoka One One Carbon X.
The Carbon X is one of two ultra-friendly shoes that feature Hoka One One’s bleeding edge combination of outsize sole, Metarocker and a carbon fibre plate.
The Metarocker has long been a feature in Hoka One One’s shoes – and definitely predates ASICS’s curved sole. It features twice the midsole volume to most standard shoes in a curved shape that allows the runner to move through the gait cycle in a rolling fashion, maximising efficiency.
With Carbon X soles that rocker midsole is further supported by a carbon fibre plate that runs the length of the shoe from heel to toe. According to Hoka One One, this improves the efficiency of the rocker and encourages a quicker foot turnover with the aim of making you feel fast when you put the shoes on.
Walmsley’s record-breaking run suggests it works and Runner’s World’s tester who got to run in the Carbon X at the record-breaking run in California agrees. “Fresh out the box, the effect of such an obvious rocker is unsettling – like you might topple head over heels at any moment,” says Isaac Williams. “But after a couple of acclimatising runs the rocker’s effectiveness shines through, and that rolling gait cycle kicks into gear.”
At £160, you won’t have to spend as much to get a taste of the Carbon X tech either.
Who benefits most: Runners who want to go long, fast.
On Running Cloudswift
In addition to the unique CloudTec cushions that made On’s shoes instantly stand out from the rest, the Swiss brand has also long put a plate into the midsole of its footwear. We saw this in the Cloudflash with a pebax Speedboard designed to facilitate efficient energy transfer from landing to take-off – aka forward propulsion in your run. And it’s in the latest On shoes, the Cloudswift too.
With the new Cloudswift – a shoe that’s designed specifically for urban running – the familiar Clouds have been paired with a Speedboard made from polypropylene (slightly less aggressive than pebax) and a new Helion foam, made from OBC, olefin-blocked polymers.
On’s answer to Boost, ZoomX and Flyte, Helion foam fuses stiffer foam elements with softer sections which On claims can stay light but offer good energy return, be responsive yet cushioning. It’s also better at withstanding fluctuations in temperature and is all-round more durable.
According to On they’re also able to tweak the density of the foam to control these properties and create different rides. The Cloudswift is the only shoe we’ve seen so far and in this design the Helion foam is much firmer underfoot than you get from the ZoomX or Boost. There’s none of the spongy feel when you step into the shoes and this definitely makes for a more stable run than you might find in Nike or Adidas’ flagships shoes. Though we’d also argue that these aren’t built to go ‘fast’ as the Next% are.
A set of Cloudswift will set you back £135.00.
Who benefits most: Anyone who’s looking a supportive shoe with better stability but good energy return.
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