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Glove-free: Warm hands without gloves

The U.S. Army Research Institute of Environmental Medicine (USARIEM) is developing a way to have warm hands without gloves.

warm hands without gloves

It’s called a Personal Heating Dexterity Device. Or PHD2 in jargon. It’s about having warm hands without gloves, and the dexterity that could be gained.

The U.S. Army Research Institute of Environmental Medicine (USARIEM) is in the process of engineering this device to help warm the hands and fingers in cold conditions.

The starting hypothesis was: if you warm your face or forearms, will it in turn increase blood flow too your hands.

My question: does it increase blood flow to your hands if your hands are above your forearms?

For the Army, the obvious use case is reloading ammunition in cold weather; not surprisingly, the loss of hand function in the cold can have a negative impact on performance, survivability and lethality. Just like in our industry, but swap “lethality” for “profitability”.

USARMIEM has been working on a way to achieve warm hands without gloves for the past few years. Now they have announced a new product: a device that heats your forearms to increase blood circulation to your fingertips.

John Castellani, the principal investigator of the project, 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. He hears a lot about cold-weather stiffness in fingers. Tell me. Castellani estimates that the current solution–gloves and mittens–degrade dexterity “50 to 80 percent.” Not to mention how they screw up texting and other touch tasks.

Castellani, who has been working with USARIEM on cold weather solutions since 1995, says our fingers get stiff in the cold because of the impact on synovial fluid, or joint fluid, which fills the cavity between two bones and serves as a lubricant. Decreasing tissue temperatures, he says, impacts hand function in strength, power, mobility, and nerve conduction.

Additionally, the body naturally diverts blood from the extremities to keep internal organs warm; when the organs are warm enough blood flows back to the fingers. “Warm blood coming from the core keeps the hands and fingers warmer,” Castellani says. “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.”

With this in mind, researchers have spent the past 80 years developing technology for different parts of the body, in an effort to increase blood flow in the hands without obstructing hand movement. Put another way–taxpayers have spent nearly a century chasing warm hands without gloves. Researchers have successfully developed warming devices for the torso, that in turn warms the hands, but the technology has not been practical for operations. Such a device would have required a lot of power to function. Each soldier would have had to carry a heavy power source along with the rest of their load.

USARIEM researchers set out to create something small and unobtrusive for a soldier on the move.

Castellani’s team reasoned that by increasing blood flow just above the hand, some of that warmth would travel to the fingers. The team also focused on warming the face because previous research had suggested there were nerves in the cheeks and forehead that, when they got cold, caused blood flow to decrease in the hands.

In 2018, Castellani and his team conducted a study to show 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.The researchers wanted to test if hand dexterity and finger strength improved when warming the forearms and face individually and together. They also wanted to see if there were differences in hand dexterity when volunteers kept the device powered for the entire two hours, versus if they turned on the device after skin temperatures had already dropped.

According to an article in Popular Mechanics, at the lab in Natick, Massachusetts, Castellani’s team placed forearm and facial warming devices that resembled heating pads on eight test subjects and put them in an zero-degree Celsius environment. The subjects were instructed to remain sedentary; their fingers averaged 10-11 C.  With the heating devices attached, average finger temperature rose by about three degrees Celsius.

They measured volunteers’ hand dexterity and finger strength before, during and after the cold exposure by having volunteers load ammunition into an M16 cartridge and take the Purdue Pegboard Test, which involved picking up and moving small pegs into sockets.

“We found that just heating the forearms worked,” Castellani said. “Heating the face by itself was not effective, and heating the face and forearms together was not a significant improvement. We also found that turning on the device after the fingers had cooled significantly was just as effective as keeping it on the entire time.”

The research team is now working with the Medical Support Systems and Evacuation Project Management Office in the U.S. Army Medical Materiel Development Agency, or USAMMDA, to advance the prototype of the patent-pending PhD2, making the device more portable and user-friendly for the uniforms of the future.

“Maintaining dexterity is so important for many occupations, including Soldiers, electrical lineman and others who work outdoors,” Castellani said.

“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.”

While coming up with a device concept, Castellani says he especially focused on reducing the power requirements for maintaining higher finger temperature. The result looks pretty much like a heating pad strapped to the arm. Which means you could try your own DIY version at home. Obviously a key part of the research of the final device will be to figure out how to overcome losing heat to the environment.

This is serious though–it’s through the proof of concept stage (after 80 years). So in a few more years, it should be available to the military and Castellani expects a commercial version for civilians will follow shortly thereafter.

Or, in the meantime, someone will develop warm, dexterous, touch-friendly gloves.

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