Soldiers hauling heavy gear in high-operational-tempo environments can easily get too hot. In fact, the Army has recorded thousands of cases of heat-related injuries.

Now a multi-institutional team is working to develop sensors that can identify the warning signs over an overheated system and give commanders a warning when troops need to stop and cool down.

"You can have somebody go down from heat exhaustion, and then you have to take a soldier away from the fight. Heat exhaustion not only impacts soldiers physically, but also cognitively by affecting decision-making, which is detrimental to a mission," said Mark Buller, a principle investigator with the U.S. Army Research Institute of Environmental Medicine, or USARIEM. "By catching heat illness symptoms early, you can do something about it."

USARIEM is seeking just such an early-warning system as part of a joint project with a team from MIT Lincoln Laboratory and a Marine Corps expeditionary rifle squad. Together they are looking to combine a wearable sensor with an algorithm that will look for telltale signs of pending heat stress in simple biological markers.

Such a system would give a scientific edge to a critical detection function that today is left almost to chance. "Right now soldiers typically look at each other in buddy pairs: I keep an eye on you, you keep an eye on me. But it is all subjective," principle investigator Bill Tharion said. He was describing the common practice in terms of chemical, biological, radiological and nuclear missions, but the observation holds true across a range of activities in which soldiers are asked to operate without physiological monitoring technology.

In the past two decades, USARIEM developed dozens of physiological monitoring systems. Drawing on the experience, the present effort looks to develop a simple means of estimating core body temperature based on heart rate readings. The system would then deliver a simple readings scale of 1 to 10 to alert commanders when soldiers are getting too hot.

To develop their algorithms, the project leaders have studied real-world battlefield data generated by a Marine expeditionary rifle squad on patrol in Iraq, data captured by Marines during jungle warfare training in Okinawa and various other sources.

Service members at at Hanscom Air Force Base participate in testing of new body-temperature monitoring systems.

Photo Credit: U.S. Army Research Institute of Environmental Medicine

While the commercial marketplace has seen a rapid proliferation of wearable physiology gadgets, the military planners say FitBit and similar devices are not sufficient to the war fighter's needs.

Lincoln Laboratory and USARIEM have tested commercial systems with the Army's 22nd Chemical Battalion of Aberdeen Proving Ground, Maryland, and with the National Guard's 1st and 95th civil support teams of Hanscom Air Force Base, Massachusetts, and Hayward, California, respectively. Those off-the-shelf products proved inadequate.

First, there are fundamental problems surrounding accuracy. "A lot of the algorithms are very broad, very general, and you have a lot of error," Buller said.

Battery life isn't up to snuff, and such devices also have inherent security issues. "They are locked into cloud storage and cloud processing. Do we really want to put information on the health state of our soldiers into the cloud? That is an area of concern," Buller added.

Rather than go the commercial route, researchers instead have opted to build their system on a government-owned, open-architecture sensor-and-communications assembly known as the Open Body Area Network, or OBAN.

Just as the military eschews an off-the-shelf fix to the overheating problem, USARIEM also has been working to develop unique technologies around other physiological concerns.

Last year, for example, Buller's team announced it was working on wearable sensors to address acute mountain sickness, running tests at the Maher Memorial Altitude Laboratory on the 14,115-foot summit of Pikes Peak in Colorado. For some soldiers operating at high altitudes, symptoms can include headaches, vomiting, fatigue, exhaustion and trouble sleeping.

For the heat-stress solution, researchers right now are working with a chest belt, but they recognize some soldier find this intrusive. The long-term goal is to develop a wrist-worn solution.

The end product also will need to corporate a wireless communications component in order to relay soldier status back to commanders. The communications protocols haven't been fine-tuned yet, but will likely be built on a tunable narrow-band connection in order to ensure electronic security. "It's not going to light up the battlefield, it's not going to pinpoint where they are," Buller said.

The new sensor system could soon see the light of day. Planners expect to put 20 prototypes in the field this summer, with the Marine expeditionary rifle squad and some National Guard teams expected to come on as early users in about three years.