When it comes to innovation in running gear, it’s usually shoes that get the most attention, especially since the best carbon plate running shoes have helped to usher in a new era of record-breaking feats.
However, shoes are not the only area where brands are pushing boundaries, and even though Nike just launched its fastest trail-running shoe ever in the ACG Ultrafly, it’s the brand’s new running top that’s making headlines.
The Radical AirFlow garment is a wild-looking t-shirt designed to help keep you cool and comfortable on your longest runs, especially on the trails. It has already been tested to great effect by Nike’s athletes, most notably by Caleb Olson, when he wore the top while winning the Western States 100-mile race in June.
A shirt full of holes
The top uses Nike’s Radical AirFlow material, which is covered in holes to improve airflow to the skin and speed up sweat evaporation, helping to cool down athletes.
The design of the top is inspired by the Bernoulli Principle of fluid dynamics, specifically the Venturi Effect, with every aspect of the top considered to promote airflow to the skin.
“We tried all kinds of airduct configurations, sizes and zonal placements throughout the testing and development,” says Jahan Behbahany, Senior Director, Nike Apparel Innovation.
“We found that a funnel-shaped construction of larger to smaller gradient holes, uniformly placed, would best ‘funnel’ and accelerate air to the skin.”
Along with the smaller holes that cover the whole top, there are larger cutouts under the arms and at the elbows, which boost ventilation and comfort, reducing the risk of chafing in those sensitive areas.
The top is also cropped, improving airflow to the abdomen and making it easier for athletes to access their waist belt during ultramarathons.
As well as boosting how quickly sweat evaporates from skin, the materials used for the top dry quickly and absorb less sweat and water than other tops.
The radical design might make it hard to convince the average runner to buy and wear — it looks cool when you’re winning Western States, but might be trickier to pull off on your local trails — but if the benefits are there, I’m sure plenty of runners will be keen to give it a try,
You’ll have to wait until 2026 to do so, however, because only Nike elite athletes will be using the top in 2025 while it continues to be developed ahead of a retail launch next year.
A super-shoe for the trails
The ACG Ultrafly might not be quite as eye-catching as the new t-shirt, but it’s probably more likely to be bought and used by everyday athletes.
It’s the successor to the Nike Ultrafly Trail, the first Nike trail shoe to use a carbon plate, and the new model has been redesigned to be lighter and more flexible than its predecessor.
A new spine split in the carbon plate means the shoe can flex more on uneven ground, and the upper has been changed to be more breathable and drain faster.
The midsole is still made from Nike’s springy ZoomX foam, as is the sockliner, while a Vibram Litebase outsole provides grip on a wide range of surfaces.
Like the new Radical AirFlow top, the Nike ACG Ultrafly won’t be available until 2026, and price hasn’t been revealed yet, though it will probably be similar to the $270 / £230 Ultrafly Trail.
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