BRA N°42: The first sports bra designed for runners suffering from chafing and burns
HÄSTKO was born in Chamonix Mont-Blanc, the global epicenter of trail running. Here, everyone runs – some fast, some slow, for a few kilometers or ultra distances. But one thing unites us: a love for the sport, and the drive to innovate so we can run better, longer, and pain-free.
A troubling discovery
Over the past few months, our team has been receiving more and more messages – and photos – from women. Runners. Desperate. They all ask the same question:
👉 “Are your bras anti-chafing?”
These women, whether they run on road or trail, are dealing with the same recurring issue: friction, irritation, and even second-degree burns caused by sports bras not adapted to the demands of running. Many of them are left with permanent scars – both physical and mental. Some have been suffering for years, with no real solution offered by the industry. We already had a couple of popular models – BRA N°38 and BRA N°92 – which work well for many women. But when it comes to extreme cases, they weren’t designed with the precise needs of running in mind. And in running, the details matter more than ever.
Running demands ultra-specific design
Running, especially over long distances and in harsh conditions – like a marathon in 35°C heat or a rainy ultra-trail – requires a completely different level of performance. Every element counts:
- No visible seams
- No adjusters or hardware
- Fabrics suited for ultra-sensitive skins
- Anatomical cuts that eliminate pressure points
That’s how the BRA N°42 project began. A bold challenge we took on with passion, over 18 months of developmentand 7 months of field testing with women who had one thing in common: they couldn’t run without getting injured.
A revolutionary prototype, tested and approved
By September, we had a solid first prototype, developed with our internal test team and the help of professional athletes like Stephanie Howe.
- Fully bonded, thermoformed, and 3D-printed
- Zero points of friction
- No adjusters, no seams, no compromise
- Bonded ventilation zones for optimal body temperature regulation
- Molded support that encapsulates the chest without pressure
- Balanced compression that supports without restricting breathing
93% of testers immediately reported a significant improvement: no more irritation, solid support, and a whole new level of comfort. However, three testers – all road marathoners – still experienced minor irritation around the neckline. Small detail, big impact.
We went back to the drawing board, tweaking the pattern, adjusting the neckline height, testing softer edge finishes, and optimizing the choice of materials. After several rounds of refinements, we achieved what we were aiming for.
Their feedback says it best:
"It's the first time I've finished a marathon without any burns."
"I honesty thought this wasn't possible anymore."
Simple, honest words – and proof that the product truly works, even for the most sensitive runners in the harshest conditions.
More than just preventing: this bra protects
BRA N°42 is not just a bra that prevents chafing – it actively protects. Even when worn under a hydration vest. Even on a 42K asphalt road under blazing sun. Even on an ultra trail in the rain. This is a bra designed without compromise, shaped by real stories, and validated 100% by those who needed it most.
What’s next?
The next challenge is just as exciting: making this bra accessible to all body types. Having no adjusters means reduced friction, but it also requires a near-perfect fit straight out of the box. Today, BRA N°42 is available in 5 standard sizes (XS to XL). A strong foundation, but still limiting for certain shapes – especially women with smaller rib cages and larger cup sizes (e.g. a 32E), who won’t get the right support from the current sizing.
👉 We’re already working on it: expanding the size range to ensure every passionate runner can finally run without pain.
Without compromise. Without injury. And most importantly, without giving up.
HÄSTKO Team
