The Race to Sub-100 Grams: How Tech and Robots are Revolutionizing Marathon Running Shoes

Elite runners broke the two-hour barrier in a homologated race using sub-100-gram shoes.

The Sub-100-Gram Competitive Arms Race

Shoe manufacturers are racing to build competition footwear weighing under 100 grams using robotic assembly, specialized foams, and hollowed carbon plates. The central engineering challenge remains shedding every possible gram without sacrificing stability or forward propulsion over a 42-kilometer race distance.

A robotic arm recently demonstrated this technique by drawing with 1,500 meters of yellow and white filament onto a shoe mold. The process takes three minutes, producing a laceless upper designed to be extremely light, EL Mundo reported.

This automated construction method, known as LightSpray, was developed by Swiss brand On.

How Major Brands Cut Weight

Adidas initiated this aggressive diet trend with an ethereal, vaporous foam in its Pro Evo line. Mizuno subsequently engineered its Hyperwarp 96 model down to 96 grams, utilizing an upper built from an ethereal structure of powdered polyurethane.

New Balance integrated a transparent mesh that allows runners to clearly see their socks inside the SuperComp Elite. Meanwhile, Puma incorporated nitrogen-infused foams, and China’s 361° designed a hollow carbon plate to reduce material weight while maintaining structural rigidity.

“Weighing each component, we try to eliminate the material that the runner is not going to use,” Conor Cashin, running product manager at Puma, told EL Mundo regarding the Fast-R NITRO Elite shoes. Puma established its Nitro Lab near its German headquarters in Dillenburg to accelerate development, joining brands like On that maintain dedicated research facilities in Zurich.

“We keep investigating. With LightSpray, for example, we have reduced the weight of the upper of the shoe by half. If a car travels at the same speed consuming less fuel, it is more efficient,” Nils Arne Altrogge, spokesperson for On, told EL Mundo.

Carbon-Fiber Plates and Advanced Foams Drive Faster Running

This design obsession represents the second major evolution of the so-called magic shoes. A decade ago, carbon-fiber plates, combined with advanced foams, changed the way marathon footwear was designed. The technology, then led by Nike with its Vaporfly, stopped being limited to protecting the foot and began helping to run faster, creating a spring-like effect that caused records to fall and sales to soar.

Adidas disrupted that market with its Adizero Adios Pro Evo 3 shoes, which weigh approximately 97 grams and were produced in a limited run of 500 pairs.

Wearing this model, Kenyan runner Sabastian Sawe finished the London Marathon in 1 hour, 59 minutes, and 30 seconds last April, becoming the first man to break the two-hour barrier in a homologated race. Ethiopian runner Yomif Kejelcha followed closely behind in the same model, also breaking the historic barrier.

Extreme Lightness Transforms Racing Shoes into Luxury Items

Mizuno manufactured its Hyperwarp 96 in a limited batch of 696 pairs priced near 500 euros, utilizing a milling process on an original foam slab to extract individual midsole components, according to Shungo Sudo, running shoe development manager at Mizuno. Sudo said that extreme lightness has effectively transformed elite racing shoes into luxury items.

Engineers caution that aggressive weight-cutting introduces distinct structural risks. “We can reduce weight with relative ease, for example, by lowering the height of the midsole or narrowing the base of the sole. However, if we reduce the height, the bounce will be worse. And if we narrow the base, the shoe will lose stability,” Sudo told EL Mundo.

Morfesi added that low-density foams frequently create stability challenges as midsole heights increase. Brand developers continue to test the limits of mass reduction, weighing whether future designs could approach weights as low as 50 or 60 grams like a tennis ball.

“Success will be measured by the optimal balance of weight, energy return, propulsion, cushioning, traction, and stability,” Morfesi told EL Mundo.