With Its Most Technical Shoe to Date, Can On Conquer Trail Running’s Highest Peak?

Chamonix, France.

Surrounded by dramatic vistas, which includes the towering peak of Mont Blanc, this might seem like a textbook example of the middle of nowhere.

But once a year, the sleepy village of less than 10,000 permanent residents becomes the most important place in all of trail running: the starting line of Ultra-Trail du Mont-Blanc (UTMB), a 106-mile foot race that passes through three countries and features an elevation gain of nearly 33,000 feet — equivalent to climbing Mount Everest from sea level.

Runners who win it are crowned trail running’s greatest talents, with the shoes they wear along the way deemed the pinnacle of innovation and technology.

With its first-ever super shoe for the trails, the Cloudultra Pro, On will show up to this year’s race not only ready to compete but hoping to win. After all, the shoe was designed for that sole purpose.

Jack Seemer for Gear Patrol

Speed through efficiency

“When we started this whole project, we didn’t start with the specs at all,” said Sergi Jansa, an accomplished trail runner who also works as a product manager for On’s Outdoor division.

That means that instead of chasing trends that determine stack height, foams and overall geometry, Jansa and his team thought about the demands of a race like UTMB, then backed into a formula they believed would give their athletes the best chance at winning.

Jack Seemer for Gear Patrol

“We looked at data that was already out there, on where the big moves are happening. And we found out that normally from Grand Col Ferret to La Fouly, if you come out first from that long downhill, your chances of winning go way higher,” Jansa says.

Just before that segment, the course climbs over 2,400 feet in just 2.49 miles — a brutal uphill that most pros tackle at sunrise, after hours of racing when the temperatures are at their coldest and both mind and body are truly tested.

So for On, designing the Cloudultra Pro became less about maximizing raw speed and more a matter of efficiency.

Jack Seemer for Gear Patrol

“If you split the race in half, you will see obviously that there are slower paces [in the second half]. When we saw that, we said, ‘Okay, speed is important but probably what’s most important is to save energy,” Jansa adds.

“How do you stay strong when everyone else is failing?”

Comfort comes first

To try and answer that, On’s Outdoor division has worked on the Cloudultra Pro since 2022, using insights and innovations from elsewhere in the company while also developing new ones.

The foam, Helion HF, is the same one featured in the brand’s wildly innovative Cloudboom Strike LS used by Hellen Obiri to win last year’s Boston Marathon. And though it’s already made waves on the roads, this represents the first time On has used it in a trail shoe.

Jack Seemer for Gear Patrol

But foams can only get you so far, especially in a setting like UTMB, where Salomon, The North Face and Hoka also bring their best-in-class compounds.

The Cloudultra Pro starts to diverge from the competition is that other factors, such as a less-aggressive rocker and padded heel cup, actually look somewhat pedestrian. That’s on purpose, and driven by athlete testing.

“That’s one piece of feedback we got,” Jansa says, who often fielded input like, “‘I feel comfortable spending nineteen hours in a shoe with a normal construction.'”

Jack Seemer for Gear Patrol

Fixer upper

None of that is to say the shoe doesn’t boast some cutting-edge technology, even on the upper. Here, On went with a new mesh material called Leno wave, which serves a variety of roles.

First, it keeps the Cloudultra Pro relatively lightweight, despite the emphasis on comfort elsewhere. A size 10 men’s clocks in at 9.7 ounces (275 grams).

Jack Seemer for Gear Patrol

Jack Seemer for Gear Patrol

But the unique upper also gives the shoe unmatched breathability and hydrophobic properties, so athletes don’t have to run hours on end in soaked shoes, should they encounter a little mud along the UTMB course.

“If you soak it in a river, it gets dry in like a hundred, two-hundred meters,” Jansa says.

It also has a new Missiongrip outsole pattern with 3.5mm lugs, optimized with Finite Element Analysis (FEA) — an advanced computer-based technique common in F1 to understand how the design of object will behave in the real world.

Jack Seemer for Gear Patrol

But perhaps even more novel are the so-called “Clouds,” those little cutouts in the midsole that are one of the chief attributes of any On shoe. Only here, their purpose is not to act as responsive springboards — as is the case on most of the brand’s offerings — but add stability.

“When we started this project, we didn’t really have an idea of how to use the Clouds,” Jansa says. But with a high-stack trail shoe — the Cloudultra Pro measures 39mm with a 6mm drop — some sort of stabilizer becomes essential, especially for a long, demanding race like UTMB.

The solution, ultimately, was one of subtraction, not addition, with the cutouts sitting right below the top midsole layer.

“Having these channels right below the top midsole makes that area slightly more fragile so that when you step on the center, you basically get centered,” Jansa says.

Jack Seemer for Gear Patrol

Availability and pricing

All that said, the beauty of a race as varied as UTMB means that anything optimized for it probably makes it suitable to other settings, too.

Before UTMB in August, some of On’s elite athletes — including Jeff Mogavero, Adrian Macdonald, Katie Schide and Germain Grainger — will test the Cloudultra Pro at Western States 100 and Hardrock 100.

Until then, the shoe is available to purchase from On’s official website. It costs $260 and comes in one colorway.

On

On Cloudultra Pro

• $269 at On

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