A century of mesh performance clothing

Before Nike ACG's Radical AirFlow, there was string underwear

Jul 17, 2026

∙ Paid

This April, I spent four days in the basement of Utah State University pulling faded catalogs from olive-gray archival boxes in the Outdoor Recreation Archive. I’d crack a book from the 1970s looking for anything related to wool, flip a few pages, and get distracted by the same thing: men in fishnet undergarments.

I’m not even kidding. Look:

Upper left, from the 1973-74 Fall & Winter Norm Thompson catalog: “Norse-Net”as full of surprises as it is holes. Actually a thermal undershirt! Full of holes to keep you warm in the winter, cool in the summer, comfortable all the time. Wear it under a soft cotton T-shirt and lightweight sportswear while you’re skiing, hiking or hunting in the winter. You’ll be surprised at the warmth it provides. In the summer, you’ll stay cool and dry when you wear it alone, or under a light cotton sportshirt. Great for golf, tennis, beachcombing and cycling.

I would have laughed it off as another oddball artifact from the outdoor industry's past—along with the mildly pornographic photoshoots from the tent maker Stephenson’s Warmlite—if I hadn't seen nearly the same garment weeks earlier.

At a Nike press event, I'd received my very own ACG Radical AirFlow top, with hundreds of holes and two armpit cutouts—like the expandable foam nets for pears but human-sized with sleeves. The weird shirt had been coming across my feed ever since Caleb Olson won Western States 2025 wearing an early prototype. Nike designers had hung its hat on the garment as “radical” and innovative.

Then in the archive, I discovered it wasn’t really new at all—just reverse engineered to keep you cool rather than warm. In fact, this kind of holey tech is more than a century old. My research led me to brynje, a Norse word for a mesh-knit undergarment that kept soldiers, fishermen, and Vikings warm.

Today’s newsletter unpacks the origins of this open-knit technology and how it evolved from Viking-era undergarments to modern running apparel. Paid readers will get a guide of brands making their own versions of mesh clothing.

String underwear, health shirts, and “Norse-Net”

Follow the threads of these stringy shirts, and you won’t end up among ravers wearing neon and sequined fishnets and holding glow sticks at an electronic music festival. Rather, you end up in the brutal chill of Norway.

From what I could find, it all started with a blonde, mustachioed Norwegian guy named Fridtjof Wedel-Jarlsberg Nansen, an explorer, scientist, diplomat, and humanitarian. A well-rounded chap. In 1888, he led a team on cross-country skis to complete the first crossing of the Greenland interior.1 A few years later, he thought, how about the North Pole? Let’s see what’s up there. He devised a plan that he believed wouldn’t fail like so many past expeditions, and started assembling his team. Part of his preparations, along with building a sturdy, nimble ship, included developing clothing fit for the Arctic. There’s not much out there about what he created except that it was something of a wool netting.

He might’ve gotten the idea from Scandinavian commercial fishermen, who, as the folklore goes2, would cut up worn fishing nets and wear them beneath their wool sweaters while working in the frigid North Atlantic. The idea was that the open mesh would hold layers away from the body while trapping warm air and giving sweat and excess heat space to circulate. But who can say whether it’s true or not because that’s about all I could find on the topic.

Moving on. This idea is then built upon by another Norwegian guy named Henrik Natvig Brun, born in 1897 in Oslo. By then, Fridtjof had retired from expeditions. He went on to study oceanography and in 1922 was awarded the Nobel Peace Prize for “leading role in the repatriation of prisoners of war, in international relief work and as the League of Nations’ High Commissioner for refugees.”3

During that same decade, Henrik, who served in the army, began experimenting with clothing for soldiers—specifically undergarments. The way I imagine it, he’s cutting up men’s undies and sewing pieces back together at his dining table. For inspiration, Henrik looked to the archaic Viking chain mail armor known as brynje, made from hundreds of interlocking iron rings. It offered strong protection in combat while remaining lighter and more breathable than solid plate armor. But instead of metal, Henrik used fabric. At first he experimented with fishing nets (like those hardy Scandinavian fishermen) but later switched to cotton. He apparently knit over a thousand string shirts—hyssingtrøye—himself.4

Thus, Henrik is widely credited with inventing the modern mesh base layer in 1921. He then patented it, and working with the textile company J. Jacobsen’s Knitwear & Confection Clothing, developed and commercialized the mesh undergarments. After presenting with the Norwegian Officers Club attended by King Haakon VII in 19335, fishnets became standard issue for the Norwegian military, tested personally by First Lietenant Henrik Brun himself: “I wear it next to my skin night and day and it has become an irreplaceable undergarment to me. In addition, it must be said that it’s hygienic properties are excellent.”6

Sourced from *Inside the Westminster Menswear Archive*

Soon, string vests found an audience far beyond Scandinavia. But as with so much outdoor gear, the military was an early testing ground (see Articles Of Interest’s gear series). U.S. soldiers serving in tropical climates during WWII even wore lightweight cotton versions to promote cooling. After the war, J. Jacobsen's Knitwear & Confection Clothing—under the name Brynje—took the garments global. Even dear Sir Edmund Hillary and Sherpa Tenzing Norgay wore Brynje’s “health shirts” as they became the first people to summit Mount Everest in 1953.

It didn’t take long for competitors to begin developing their own versions. And that brings us to my scandalous discoveries in the Outdoor Recreation Archive.

To supplement my photos, Chase Anderson at the archive sent me his curation:

Some of the language used in ads, catalogs, and books:

“Originally used by Scandinavians. Underwear like this has been used for more than a century by fishermen who work in the frigid Scandinavian sub-Arctic. They call it Brinje (pronounced Brin-ya). Their line of work calls for warmth and freedom especially when they’re operating a boat or pulling in a net. We’re not sure how they discovered that underwear with holes in it would keep them warm, but these fishermen have actually used one of the basic principles of thermal insulation.” (1973-74 Fall & Winter Norm Thompson catalog)
“Raf Escape Vest, Lillywhites, 1943. During the Second World War, certain crews of the Royal Air Force were issued with this model of string vest. String vests were an ideal cold-weather garment for bomber crews flying at high altitude in subfreezing temperatures…Knitted using course cotton string, this underwear vest was produced by the sports company Lillywhites which, like many clothing manufacturers, were contracted to make uniforms for the armed services during the war.” (Inside the Westminster Menswear Archive)
“Allen-A Net Underwear. Net underwear of 50% polyester, 50% cotton. The cotton provides absorption while the nylon promotes rapid drying and increases durability. Top of shoulder of T-shirt is solid so that pack straps will not cause net pattern to bite. Unlike the picture, underarms are open mesh for maximum breathability. Pants with elasticized waist are also available.” (Unknown)
“Specialised String Underwear. Very popular underwear which keeps the body at normal temperature in both hot and cold temperatures by providing an insulating layer of air next the skin. Very comfortable and light. Made in Norway.” (Blacks Camping Equipment, 1970)

Polypropylene replaced cotton in the 1970s, and today most mesh base layers are made from synthetic fibers. Yet the purpose hasn’t changed much since Henrik Brun first experimented with fishing nets and knitted cotton. The garment may look unconventional—even a little ridiculous—but its physics still work: trap warm air, move moisture, and use less fabric than you think you need.

Nips out, y’all.

Amelia