On Cloudboom Strike LS Initial Thoughts

“Impossible!” “How is it made?” “That is insane!” “What is the point?”

Just a few first words on the LightSpray™ technology by the team as we unboxed the On Cloudboom Strike LS in The Running Channel offices today.

Swiss sportswear brand On have unveiled a brand new technology they have called LightSpray™, a revolutionary single-step process which ‘sprays’ a lightweight and high performance upper around the shoe. It is something that has to be held and felt to be understood how fundamentally groundbreaking it is. 

It feels almost impossibly light for a running shoe at just 170g (for men’s US8.5) – for comparison, the Nike Alphafly 3 weighs 201g (also in men’s US8.5). This weight advantage is down to the upper weighing just 30g. The only supershoe that’s lighter than this is the adidas Adizero Adios Pro Evo 1, which tops the scales at a featherweight 140g (for unisex US8.5).

For the average runner this small weight loss might be meaningless, but to those pushing the boundaries of what is possible in long distance running it could be the difference between first and second – or between a footnote in history and a world record. 

It had been teased on the feet of Hellen Obiri when she wore a development version of the shoe for her win at the 2024 Boston Marathon, but here at TRC assumed the upper was a wrap hiding something innovative below it, but it turns out that the all in one upper was the big innovation. 

Designed to optimise athletic performance, the LightSpray™ technology is On’s bespoke manufacturing process. It works by spraying 1.5km (yes, you read that right) of filament and fusing it directly onto the shoe as a single-piece upper. The process is automated by a robotic arm and each shoe takes just three minutes to be sprayed. 

Check out this video from On to see what the process looks like (it’s super cool and unlike anything we’ve seen before!):

The technology was developed at On Labs in Zurich and as well as being lightweight, it’s also quicker to make than regular shoes and is designed to minimise waste in the shoe manufacturing process, which together reduces the carbon emissions of the shoe’s upper by 75% compared to other On racing shoes.  

The precision-spray of the upper is seamless and doesn’t have laces, but it gives full support on your foot. It’s a marked difference from traditional running shoe uppers which involve numerous stages of production, and various materials and glues. 

What surprised us is how the upper feels. On have assured us of its durability, but we were terrified of ripping it when we first unboxed it because it feels so light. While it looks like a sock, it doesn’t feel like one. Inside, it has a smooth, silk-like feel, and the outside has a rougher texture, and it’s not something which stretches well.

One key thing that will be interesting to see is how the upper holds over time, as the sock-like snug feeling will be difficult to run in if it sags as there is no way of creating a lock-in to avoid slippage.

All this new technology comes at a cost, unsurprisingly, and with this shoe retailing at $330/€330 it is the second most expensive running shoe on the market behind the adidas Pro Evo 1. And it remains to be seen whether the On Cloudboom LS will have a similar short peak performance window like the Pro Evo 1, especially when compared to other supershoes like the Nike Alphafly or ASICS Metaspeed. 

On are calling this a ‘new era of innovation’ for the company, and for the running industry. In what feels like a space race to make the fastest and most efficient shoe on the planet, it feels like On have taken off and may blast ahead of the old guard of Nike and adidas. But is this a small step or a giant leap forward in the world of supershoes? And could On be on the feet of the first sub-two hour marathoner?