Published on July 30, 2026 04:00 am
I recently read Sebastian Junger Perfect storm-which developed from 1994 Outside Article—which describes the sinking of a Massachusetts fishing boat at sea. One passage surprised me. Junger is trying to understand why such a massive storm occurred and has referred to global warming as a possibility. I was surprised that he didn’t say that climate change was definitely a factor, until I realized that he was writing more than 30 years ago, before climate change was widely accepted as real and its effects became clear.
Today, all I have to do to understand the realities of climate change is step outside. Here in New Mexico, where I live, summers are markedly, dangerously, and perhaps forever, different. According to the National Centers for Environmental Information, summers statewide are 3.7°F warmer than in 1970, and eight of the 10 hottest summers on record have occurred in the last 23 years.
New Mexico is not unique when it comes to rising temperatures, so outdoor companies around the world are scrambling to find new technologies that will help people continue to enjoy the outdoors. As one of the most heat-intensive sports, running is often in the headlines and this summer three new heat-protecting running shirts caught my attention. Nike ACG, Satisfy, and Red all promised that their shirts could breathe and cool in new ways, so I called them up for a wear test and even sent us samples. outside the lab at CU Denver so we could run a lot of lab tests. I also ordered a more traditional Patagonia shirt that topped our spring testing of running shirts, as a control for comparison to the new technologies. The results of field and laboratory tests are given below.
Satisfy Heatcrush Base Layer
Field Test: It seems counterintuitive to pull on a long-sleeve shirt for a hot run, and when I first donned this tight-fitting base layer, I thought I’d made a mistake as the temperature felt like it had jumped up a few degrees. But as soon as I started sweating, the thin, Japanese micro-jersey material started drawing sweat from my entire upper body and my temperature was instantly regulated. Once the shirt becomes drenched with sweat, the actual heat dump begins due to a process called evaporative cooling Where the moving air is cooled as it passes through water trapped in the shirt (a process used in ordinary air conditioners). To take things up a notch, I poured a bottle of cold water on the shirt and I woke up fresher than I ever have in a hot run, having stayed cold for a full 20 minutes in 100 degree temperatures.
Lab Test: Adam Trenkamp, our Lab Test editor, ran the HeatCrush and all the other shirts through breathability, dry time, and air permeability tests, rating each shirt on a scale of 1-5 (from worst to best) for each metric. The main body of the HeatCrush shirt earned a “worst” rating of 1 for air permeability (how much air gets in), while the under-arm mesh section topped the scale with a 5.
I did notice the lack of air speed up front but realized this is by design. The material is not supposed to move as much air as possible, but rather I thought it was supposed to move some air through the retained water to create a cooling effect. The HeatCrush scored 2 points for breathability – how fast it can wick sweat away from the body – which was no surprise since it wants to wick sweat away from the skin but then keep it around for its cooling properties. Drying time was a solid 4 because the fabric is so thin. Theoretically, I would like the dry time to be slower, but I found that on the hottest days my sweat keeps the shirt quite wet, and therefore cool.
Best for: I wore the HeatCrush base layer on a few shorter races, but it’s definitely best for longer races where sweat builds up and evaporative cooling can regulate temperatures for longer periods of time. This shirt is also perfect for runs with access to water sources – be it rivers or water fountains – where I can dip it in and intensify the cooling effect.
Nike ACG Radical Airflow NXT
Field Test: The Radical Airflow NXT immediately caught my and many other runners’ attention when Caleb Olson wore it to win Western States at 2025. Full of holes and cut short, it looked like either a gimmick or something radical. After testing, I can say that in the over 10 years I’ve been testing running shirts, the NXT is easily the most innovative running shirt to hit the market.
The greatest invention is the pores, which are funnel shape So when air passes through they condense and become faster (similar to this). venturi effect in fluid dynamics). This created more airflow than I would have felt if I had been running without a shirt. Even standing around I could feel the wind hitting my arms and chest. Once I started walking, it felt as if a low-powered fan was cooling my entire upper body. The only downside I found was that the material needed to be against my skin for it to work. When I hunched over on the climb and the shirt loosened from my chest, the cold stopped taking effect.
Lab Test: As you might expect, the NXT crushed air permeability, coming in at a 5. Breathability was also a 5 for two reasons: First, there is so much airflow that it helps eliminate sweat quickly. Second, the polyester around the vents does a great job of wicking away any moisture. Dry time was the slowest of the group, rating 1, but that’s a good thing: By retaining moisture, the NXT benefits from an evaporative cooling effect similar to Heatcrush, where the air drops in temperature through retained sweat.
Best for: If I had enough confidence, I would wear NXT on all my long runs. But since it’s so awkward looking, it can only be saved for race days. We’ve seen a lot of people wearing it in the western states this year, and I expect the shirt to become more ubiquitous as more people experience the technology. But for now, it still has a strange-looking exterior.
Red Thermal Dispersion Tee
Field Test: RED is a popular brand at the moment thanks to several innovative launches. Their Backcountry Ski Pack offers an entirely new perspective on how to store your safety equipment, and their Running Belt started an industry-wide reinvention of the waist pack. I use the belt constantly and was looking forward to the Thermal Dispersion T. Unfortunately, I found it too weak.
There are plenty of body-mapped perforations (small holes) on the back and sides of the shirt to dissipate heat, but none on the front. The ventilation on the back kept me from overheating while wearing the pack, but it felt strange not having airflow over my chest. Due to the irregular mapping, the Red doesn’t trap or dump heat like the Patagonia Cap Cool Ultra, and doesn’t cool down much when blowing on moisture like the NXT or HeatCrush. I’ve seen some evaporative cooling, but nothing like what Satisfy makes. The polyester material is stretchy, comfortable, and durable—Ride says it’s “wearable in multiple environments”—but there was nothing about the shirt that made me want to reach for it instead of anything else in my drawer.
Lab Test: Trenkamp tested the air permeability of different areas on the shirt, and found that the highest score was a 4 on the back where most of the holes are located. As expected, the front section was very low: it got a 2 and other areas a 3. The back also got 5 points for breathability due to thermal dispersion, but the front and sides both got 1. Dry time was solid, on par with HeatCrush’s 4.
Best for: Given its name and the brand’s reputation, I expected the Thermal Dispersion Tee to optimize my heat tolerance, but it seems Red focused more on versatility than specificity. Based on wear testing and lab numbers, the Thermal Dispersion Tee doesn’t really fall into the same category as the other three shirts, which are, in my opinion, the best on the current market for warm weather running.
patagonia cap cool ultra shirt
Field Test: Our control shirt of the test, the Patagonia Cap Cool Ultra, doesn’t have any standout technology, but it was my favorite shirt of the group and was also the highest-ranked shirt for our Buyer’s Guide team. It rose to the top because, in addition to performing well on runs, the Cap Cool Ultra also serves as a great casual shirt. Cut to look good with running shorts or jeans, and offered in a variety of colors, this is the kind of shirt I want to wear all summer long — both during afternoon walks and at work. At $60, it’s significantly more affordable than high-tech options.
Lab Test: In terms of performance, Cap Cool Ultra received the highest average rating. It got a score of 4 for air permeability, 4 for dry time and 5 for breathability. Put together, this means that the shirt is very good at allowing air to reach your skin as well as evaporating sweat. It doesn’t have any air concentration like the NXT, and it doesn’t rely as much on evaporative cooling as the Heatcrush, but it lets your body breathe and dissipate heat effectively. I was worried that the thin polyester would be delicate and would need babying, but it’s as tough as any standard running shirt I’ve worn so far.
Best for: If I had to recommend one shirt from this test, I would start here. The Nike and Satisfy shirt will benefit professionals and highly committed runners who spend more time training and racing. The rest of us, even on longer runs, don’t need the same level of technique and can make do with a versatile shirt that lets our bodies utilize their natural cooling mechanisms.
