Last summer, an Illinois National Guard soldier collapsed just as he finished the 2-mile run for a fitness test at Camp Shelby, Mississippi. Spc. Nathaniel Jefferson, 38, was rushed to the hospital, along with a second soldier suffering from heat exhaustion, where he died. But Army researchers hope that a new system that combines sensors and data from the training of elite military units in hot weather can be a key tool for avoiding the kind of heat injuries that killed Jefferson and the hundreds of heat strokes that knock soldiers out of action every year.
The Heat Injury Prevention System, or HIPS, developed by Army researchers, includes a wearable sensor that feeds into an algorithm programmed to spot small changes in how they walk and move. The system uses data collected from over 10,000 troops training in high hight. A handful of Army and Marine Corps units use HIPS today, but researchers hope to expand its use.
“The algorithm sort of learns the individual and how they’re moving and it’s looking for a significant deviation from their regular gait pattern,” said Mark Buller, an Army scientist who developed the system. “Five minutes before that heat stroke, you really start to see that pattern degrade.”
HIPS looks for changes in a troop’s gait and their estimated core temperature. If it spots a troop’s steps starting to drag, even before fellow soldiers might notice, and the soldier shows a core temperature above 104 degrees fahrenheit, it indicates that they are at risk of a heat stroke. The sensors feed into a secure mobile application that can track the wearer’s heat risk status with green, yellow and red level indicators.
In the world of wearable technology, core temperature estimation has been difficult to measure accurately. But HIPS uses a baseline algorithm that Army researchers developed and published in 2013. For HIPS, the two algorithms at work are the heat stroke detection algorithm and adaptive physiological strain index which uses core temperature estimation, heart rate, and skin temperature. When identifying exertional heat illness, skin temperature is a key factor, which most modern commercial sensors do not measure, according to Buller.
“We know it works because we have tried it in the field and validated against 30 exertional heat illness cases,” Buller said. “Most other algorithms have not been demonstrated against heat illness cases.”
The military began implementing preventative measures for heat injuries with the Army’s heat stress index which dictates work-rest and water intake guidelines for high temperatures. By requiring that commanders use the heat tables for training in hot temperatures, the services have been able to limit severe heat-related injuries and fatalities over the years. In 1956, when Marine Corps Recruit Depot Parris Island implemented the heat stress index, there was a 50% drop in the rate of exertional heat illness.
But each year, the Army still deals with thousands of documented heat exhaustion cases and around 400 exertional heat strokes which can range in severity from regular recovery to a couple nights in the hospital to death, according to Ltc. David DeGroot, director of the Army’s Heat Center at Fort Moore, Georgia.
“It pales in comparison to things like musculoskeletal injury but given for one, the potential for a fatality and two, under the vast majority of circumstances, these are all preventable,” he said.
A review of the service’s heat injury data found that in 2023, heat illnesses were most prevalent among Black Marine Corps and Army service members younger than 20 years old. Male service members faced more heat stroke and female service members experienced greater levels of heat exhaustion.
By far the most at risk were new recruits. Researchers found that the rates of heat injury for those newest to the rigors of military training were 12.5 and 13.5 times higher than other enlisted service members and officers.
Despite official heat guidelines, its implementation still largely relies on commanders’ risk tolerance for pushing their troops through training in hot temperatures. DeGroot gave the example of Ranger school.
“Personally sitting where I do, I’m comfortable with the ranger course taking a higher level of risk because they also have two physician assistants and a platoon full of medics and they have the facilities and an aid station right there at the ranger course for rapid cooling and treatment of a suspected heat casualty,” DeGroot said.
Several units have been using HIPS in training for years. MCRD Parris Island has been using and issuing HIPS since 2021 and at Fort Leonard Wood, Missouri, the Sapper Leader Course has used them since 2019. HIPS is also made available for basic training at the Missouri base.
Marines going through reconnaissance courses have used HIPS since 2023 and officials are even incorporating HIPS into the Soldier Monitoring System over the next month for land navigation training. It will also be provided for sapper courses at Fort Leonard Wood.
HIPS
HIPS includes a wearable torso sensor from Odic Inc. and an Army-developed algorithm made from data collected between 2018 and 2023 from more than 14,000 individuals. The data includes a variety of training environments like recruits at The Crucible at Marine Corps Recruiting Depot, Parris Island, reconnaissance training at Camp Pendleton, jungle operations training at Schofield Barracks, Hawaii, and infantry One-Station Unit Training at Fort Moore, Georgia.
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The ultimate goal is to provide HIPS to trainees for their own health monitoring and to improve situational awareness, Buller said. Despite the Army’s desire to prevent heat illness, especially in the South where units prioritize prevention methods like ice water arm immersion and immediate medical aid, he said there’s no written requirement which would bring the tool to more units.
“Regular heat illness surveillance helps identify the magnitude of the impact these conditions have on service member health, training, and force readiness,” according to researchers who reviewed annual military heat injury data. “At the command and unit level, emphasis on evidence-based prevention, mitigation and risk management, with continued education on the signs, symptoms, and early field interventions for heat illness, are crucial steps in reducing the impact of heat illness morbidity.”
Buller said there needs to be a larger recognition by the Army or Department of Defense that
technology exists.
“It works well, you can manage heat. This is kind of like what’s recommended or what should be mandated in certain environments to use,” he said. “That policy level has not reached maturity yet so I think this pull is coming from individual units that want to do a better job at heat illness prevention.”
Heat injuries
Top base producers of heat casualties are Fort Campbell, Kentucky, Fort Liberty, North Carolina, Marine Corps Recruit Depot, Parris Island – all locations where humidity makes the climate seem that much hotter.
“If the air is already saturated with water, the sweat that’s collecting on our skin has nowhere to evaporate too,” DeGroot said. “It’s not sweating that cools us off. It’s the evaporation of the sweat that cools us off.”
The circumstances that have produced heat illnesses have typically varied. Last year,
a reservist in South Carolina was doing drills at Fort Jackson and another was a National Guardsman doing annual training at Camp Shelby, Mississippi. But researchers did notice one troubling trend – “on average 85% of our heat strokes were during either foot march or running events,” DeGroot said.
In an event like the Army’s standard 12-mile run, where a soldier needs to be within the three-hour time limit to earn the expert infantryman’s badge, that’s when heat injuries occur.
“It comes back to that issue of individual motivation because many of these events when they occur, they’re being performed for time. There’s a standard that they have to meet or they’re training to meet so they’re gonna push themselves,” he said.