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f you’re looking to make improvements in your athletic performance, you should start with the proper gear. When you’re pushing your body to its limit, it’s best to eliminate as many distractions as possible, so all that’s left to focus on is your training. This means eliminating itchy tags, loose fabrics and non-sweat-wicking materials. Most sweat-wicking t-shirts make sure the sweat wicks from the shirt, but not necessarily from your body, so eventually you heat up regardless of what your shirt is wicking away. A material known as 37.5 aims to eliminate those complaints.

What is 37.5? It’s a dynamic thermoregulation technology that is woven into fabric designed to keep the humidity around your skin at a minimum, so it wicks the sweat off your body before the sweat has time to turn into liquid. Brands like Adidas Outdoor, Trek, Scarpa, Salomon, Mission Athlete, Rab, Rhone, Goldwin and about 165 others already buy the fabric and incorporate it into their lines. The technology can help improve performance and sleep simply by decreasing moisture on your skin before it turns to sweat, thereby stabilizing your body temperature. But how does it work?

In 1992, Dr. Greg Haggquist, a Ph.D. photo-physical chemist, took a trip to Japan while he was researching for his post-doctoral fellowship. While visiting, he discovered the beauty of a hot volcanic sand bath at Mount Aso and the power it holds to help detoxify your body (similar to a thermal bath or sauna). Mount Aso is a hot spring-like area, but instead of water, there’s hot volcanic sand all over the ground; women help dig human-sized holes and tourists strip down and hop in to be buried up to their necks, akin to getting wrapped in a mud mask at a spa, or stepping into a steaming hot bathtub. It’s supposed to be extremely relaxing and help you sweat out toxins, but imagine being told all of that in another language that you’re not quite fluent in. Dr. Haggquist tried to understand the women’s Japanese as she tried to understand his English — it ended in Haggquist getting buried. It’s quite the sight, but Dr. Haggquist was alarmed at how hot the sand was and remembers thinking, “I’m going to jump up in the first minute or two because I’m going to overheat.” Exactly the opposite occurred — after lying buried in the hot sand for an hour, Dr. Haggquist realized he had to figure out what was going on and why he wasn’t clawing his escape from the pit of burning sand to try and cool off. It was in that moment that he unknowingly took the first step towards a miracle fabric.

The trick lies in the properties of the volcanic sand. While you’re sitting there sweating buckets, the sand “sucks up perspiration before it becomes liquid,” or more simply, before it turns into sweat. The sand sucks up the surrounding humidity around your skin, which allows your body to continuously cool itself. It was a relatively simple concept, and Dr. Haggquist decided to attempt to turn it into a fabric that can be worn during both exercise (and daily life). In theory, with the new fabric the body could be in a constant state of cooling.

But you can’t just put volcanic sand in a t-shirt and call it a day. “How am I going to dry out the environment above your skin?” Dr. Haggquist wondered. He needed a desiccant, something that sucks up water, “like those bags that say ‘do not eat’ that they put inside electronics,” he says. But he also needed energy. “The human body releases light, we just can’t see it because it’s infrared,” he says. “The light is constantly released and lost in the environment around us, but I know the wavelength: eight to 15 microns. So what I needed was a semi-desiccant material that absorbs that exact amount of light. Once I did that, and put it on the body, magic happened.” And thus 37.5 was born.

“My motto is ‘keep your jacket on.’ It’s working in the jacket to pull the humidity off of you and that’s going to keep you comfortable so when you’re wearing a sports coat or jacket, you can continue to wear it and you’re not going to overheat,” Dr. Haggquist added. “Once you start to overheat, you create humidity and that humidity comes off your body and is sucked into the fabric. So it’s going to keep you warm or cool, depending on what you need.”

The numerical name comes from the ideal core body temperature, which is exactly 37.5 degrees Celsius. It helps keep the environment around your skin at its ideal relative humidity of 37.5 percent, providing a Goldilocks effect: not too hot, and not too cold.

Once the team spun the 37.5 technology into materials, they began working with outdoor brands. Beginning with a Cannondale cycling jersey that won Time Magazine’s Most Amazing Invention in 2005, 37.5 quickly found success in the outdoor space. Recently, Mission Workshop, the brand that builds high-end minimalist weatherproof bags and technical apparel out of San Francisco, began to add 37.5 into its own products. Jeff Roberts, the head of the company’s apparel design team, echoes the sentiment that 37.5 is unique. “There are a million different textile technologies that have come out in the last 10 to 20 years, and I had pretty much tuned them all out,” he says. But 37.5 was different. It allowed Mission Workshop to use polyester in clothing and prevent it from holding bacteria and stinking at the end of a bike commute, for instance. “It’s not the cheapest technology by a longshot,” Robers acknowledges, but you get what you pay for. “We have people who are cruising into work wearing it, and I’ve worn it myself for five days straight without a shower.”

37.5 has been tested over and over again by third parties because it’s a hard technology to wrap your head around without testing it. The most important difference between wearing something woven with 37.5 technology and opting for something that’s sweat-wicking is that one works with your body and the other addresses what’s happening to the shirt. “We’re probably the most tested technology out there. Mostly [the other guys] are taking the fabric and saying, ‘Look at my fabric, it absorbs and moves the water all over the place. This is really good for you.’ What we’re doing is we’re putting it on people and looking at comfort and performance,” Dr. Haggquist says. “And people are saying, ‘Yeah, this is more comfortable and yeah, I’m performing better.’ It’s almost like doping. Screw blood doping, use our stuff. Dope the fabric and you’re going to get the performance [benefits] — and it’s legal.”

Gear with 37.5

37.5 technology works in a variety of fabrics and materials. Companies mix it into everything from towels to jackets, sheets to sweaters. It can even go into silk and blend with a high fashion piece. The options are endless, so we pulled together a brief sampling of items that have been recommended to us or that we’ve tested and experienced the cooling properties firsthand. Head to the 37.5 site to check out more options.

Carhartt Base Force Extremes Lightweight Boxer Brief

Thanks to 37.5 technology, these boxer briefs dry incredibly fast so that you’re always comfortable on hot days. Jeff Roberts, the head of Mission Workshop’s apparel design team, agrees that these are great, and wears them every day.

Mission Workshop Base Layers

This short sleeve base layer will cool you down when temperatures rise and heat you up when it’s cold. The base layers from Mission Workshop are one of Roberts’s favorite pieces. Look for long sleeve tops and bottoms coming later this month.

Buffy Comforter

The plant-based comforter is just as soft as any comforter, plus it heats up and cools down to facilitate much-needed rest.

Adidas Outdoor Terrex Stockhorn Hoodie

A fleece hoodie woven with 37.5 fabric technologies will be your best friend when you’re climbing a mountain.