The Army Found a Way to Keep Your Hands Warm Without Gloves

4 min readHere’s what you’ll learn when you read this story:The U.S. Army Research Institute of Environmental Medicine (USARIEM) is in the process of engineering what it calls the Personal Heating Dexterity Device to help warm the hands and fingers in cold conditions.Because hand coverings greatly reduce dexterity, the research team came up with a way to warm the hands without gloves. The researchers tested forearm and facial warming devices in cold conditions to see if increased blood flow to those areas, above the hands, would also increase blood flow to the fingers (it did).It’s tough to tap out a text while wearing a thick pair of gloves. Now imagine being a soldier and trying to reload your gun while wearing them. The U.S. Army Research Institute of Environmental Medicine (USARIEM) intimately understands this problem. For about a decade, it’s been working on a solution—a device that heats your forearms to increase blood circulation to your fingertips, all without gloves.During a field test of the prototype heated arm sleeve in Alaska earlier this year, the device boosted manual dexterity by up to 50 percent in some cases, according to a January 2026 statement from the U.S. Army Medical Research & Development Command. That could be a lifesaving improvement for soldiers who are loading ammunition, handling equipment, and treating those with injuries.Known as the Personal Heating Dexterity Device, the product may seem like magic, but it’s just science. That’s according to John Castellani, the principal investigator of the project, who is a research physiologist and an expert on cold weather. Most of his work at USARIEM has been on soldier performance and reducing injuries during cold-weather operations. One of the greatest complaints among those who work outside, he said in an a 2020 interview, is the stiffness of their hands in the cold elements.“Anyone who has ever tried to do anything with their hands and fingers in the cold knows that it is hard to do when wearing gloves, because that degrades dexterity 50 to 80 percent,” Castellani told Popular Mechanics. “And taking off the gloves helps, but then the hands get really cold and cannot work well anymore because of the lack of blood flow to the fingers.”Castellani, who has been working with USARIEM on cold weather solutions since 1995, said our fingers get stiff in the cold because the harsh weather conditions have a direct impact on synovial fluid, or joint fluid, which fills the cavity between two bones and serves as a lubricant. Decreasing tissue temperatures, he said, impacts hand function in strength, power, mobility, and nerve conduction.The biggest issue, though, is the lack of blood flow. “Warm blood coming from the core keeps the hands and fingers warmer,” Castellani said. “One way to keep the hands warm is through vigorous activity; exercise will raise the core temperature, even in the cold, and that warm blood can keep the hands warm also.”Castellani said runners experience this in the cold, too. They begin wearing gloves but eventually take them off as their body heats during the exercise.USPTO/CastellaniIn 2018, Castellani and his team conducted a study to see if heating parts of the body that are above the fingers—like the forearms or even the face—could improve blood circulation and therefore increase the temperature of participants’ fingers as a result.At the lab in Natick, Massachusetts, Castellani’s team placed forearm and facial warming devices that resembled heating pads on eight test subjects. While inside a special environmental chamber that can simulate the cold—here, exactly zero degrees Celsius, the freezing point—the participants remained sedentary. Their fingers, on average, were between 10 and 11 degrees Celsius under those conditions. Once the heating devices were attached, Castellani and his team found that average finger temperature rose by about three degrees Celsius.“The magic number we would like to get to is 15 degrees Celsius, which is a breakpoint finger skin temperature,” he said. “But our three-degree increase improved dexterity about 50 percent, [which is] a good start.”USARIEMWhile coming up with a device concept, Castellani said he especially focused on reducing the power requirements for maintaining higher finger temperature. Scientists have been developing cold weather technology for various parts of the body for over 80 years, he said, but the technology isn’t practical for operations. To wear any such devices, soldiers would have to carry along heavy power sources along with the rest of their load.So the USARIEM researchers wanted to create something small, unobtrusive, and battery operated. Castellani said they targeted forearm heating because it’s “essentially just heating the tissue proximal to the hand.” The scientists applied warming patches to the face because physiology says cooling the face causes constriction of the blood vessels that supply the hands and feet.“We thought heating this area might trick the body into thinking it needed to move blood and heat there to dissipate heat,” said Castellani. “It didn’t prove so.” The final device, then, will only involve heating the forearms.The USARIEM did not respond to a request for an update on the Personal Dexterity Heating Device, but the January statement from the Army’s Medical Research & Development Command notes that the device has been transferred to its Warfighter Health, Protection and Evacuation Program Management Office to further develop the product.It’s unclear what the final device will look like, but when we spoke to Castellani in 2020, he said the biggest challenge is getting as much heat to the arm as possible without losing it to the environment, so that will be taken into consideration during the design process. At the time, Castellani also expected a commercial version for civilians would follow.“There are many people who would like a product like this—line workers in the winter, construction workers, mechanics, winter athletes, [and] people who get really cold hands,” he said.Before joining Pop Mech, Courtney was the technology reporter at her hometown newspaper, the Pittsburgh Post-Gazette. She is a graduate of the University of Pittsburgh, where she studied English and economics. Her favorite topics include, but are not limited to: the giant squid, punk rock, and robotics. She lives in Philadelphia with her husband, her black cat, and towers upon towers of books.