By Rob Shaul, Founder
Wildland firefight is one of the most physically demanding jobs on the planet. A recent study published in Comprehensive Physiology in 2023 offers a detailed examination of the extreme physical demands placed on these tactical athletes, including that wildland fire hand crews can burn up to 6,260 calories in a single day while on the fireline.
Extreme Energy Demands and Total Daily Energy Expenditure (TDEE)
The 2023 study, Physiology of the Wildland Firefighter: Managing Extreme Energy Demands in Hostile,Smoky, Mountainous Environments (Ruby, Coker, Sol, Quindry, Montain) compiled previous previous wildland fire research and measured the total daily energy expenditure (TDEE) of wildland firefighters, finding that it ranges from 12.3 to 26.2 megajoules per day (MJ/day), which translates to approximately 2,946 to 6,260 calories per day. This wide range reflects the varying intensity and duration of the tasks performed, as well as the environmental conditions firefighters encounter. The upper limit of this range, 6,260 calories, represents one of the highest energy expenditures recorded for any occupational group and rivals that of soldiers in combat environments, Tour de France cyclists, Military Special Forces Training, and high-volume swim training. See below:
The energy demands are primarily driven by the physically taxing nature of wildland firefighting, which involves prolonged periods of strenuous activity, often in harsh and hazardous environments. The study utilized the doubly labeled water (DLW) method, the gold standard for measuring energy expenditure in free-living individuals, to obtain these precise measurements .
Breakdown of Physical Tasks and Their Energy Costs
The study provides a detailed breakdown of the specific tasks that contribute to the high energy expenditure:
- Walking and Hiking: Firefighters often hike long distances over rugged terrain while carrying heavy gear, which includes tools, water, and protective equipment. The energy cost of walking was measured at approximately 6.6 kcal/min. The study noted that ingress hikes—where firefighters move into the fire zone—can last between 20 to 60 minutes, with an average speed of 3.4 km/h over terrain with an average grade of 4%. This equates to approximately 28 minute per mile hiking uphill under load. These hikes often occur in the early part of the day when temperatures are lower, but conditions quickly become more challenging as the day progresses .
- Chainsaw Operations: Operating a chainsaw, essential for clearing trees and creating firebreaks, burns around 5.0 kcal/min. This task is not only physically demanding due to the weight and vibration of the chainsaw but also requires sustained effort and precision, often in difficult terrain .
- Raking: Raking is one of the most energy-intensive activities firefighters engage in. It involves creating firebreaks by removing vegetation and other flammable materials. The study found that normal raking consumes approximately 9.4 kcal/min, while urgent raking, which is performed in more critical situations, can burn up to 14.4 kcal/min
- Loading: Hand crew men averaged 86, plus or minus 11.6 kg in bodyweight; with women averaging 68.6, plus or minus, 8.4 kg. However, loading for both men and women was the same – with men averaging a load of 18.7kg plus/minus 3.7 kg, and women averaging 18.2kg plus/minus 3.6kg. Overall, men are carrying 22% of their bodyweight fighting on the fireline, and women are carrying 27% of their bodyweight.
Intensity and Duration of Work
Wildland firefighters typically work shifts that last from 12 to 16 hours, during which they perform a mix of high, moderate, and light-intensity tasks. The study found that high-intensity tasks, such as digging firelines and hiking over challenging terrain, consume nearly 28% of a firefighter’s shift. These tasks require sustained physical effort, with firefighters’ heart rates often exceeding 135 beats per minute (bpm) during these activities.
The study also revealed that during these high-intensity tasks, some firefighters maintained heart rates above 135 bpm for 20% to 75% of their shift, depending on their role and the specific demands of the day. This sustained cardiovascular strain is a clear indicator of the extreme physical demands placed on their bodies.
Nutritional Intake and Hydration
Despite the extreme energy demands, firefighters generally maintained stable body mass over the course of their shifts, suggesting that their energy intake, while slightly below the calculated TDEE, was sufficient to prevent significant weight loss.
On average, firefighters consumed about 15.2 MJ/day (approximately 3,632 calories/day), which is below the average TDEE of 17.5 MJ/day (approximately 4,183 calories/day).
Despite this caloric deficit, wildland firefigthers don’t experience weight loss fighting fires. The Researchers write that overall, body mass was maintained during the fire season, with an overall average of 77kg (both men and women averaged together).
In terms of water, the researchers found that wildand hand crew firefighter lose 6-10 liters per day on the fireline.
The study also found that hand crew firefighters’ diets were typically high in carbohydrates, averaging 6.5 to 7.3 grams of carbohydrates per kilogram of body weight per day. However, this intake is still lower than the optimal level recommended for endurance athletes, which could impact their performance during extended periods of high-intensity work. Logistical challenges, such as the difficulty of providing carbohydrate-rich foods in remote areas, further complicate the ability to meet these nutritional needs. Reserchers noted that when supplied with MREs, wildland firefighers did not consume enough carbs to keep up with their energy burn.
Takeaways and Next Steps
This study compiled data from several previous studies researching the physical and other demands for wildland fighters, but to our knowledge, the reasearchers did not conduct original research. And despite the rapidly increasing number and intensity of wildland fires world-wide, and how much depends on wildland firefighters, current research is paltry, especially given the data that can be compiled over long durations via wearable technology.
Research needs to be completed on the fireline, and season-long fitness demands for wildlire hand crews, hotshots, truck crews and smokejumpers, and this data needs to be used to generate appropriate fitness assessments and pre-season fitness strength and conditioning programming.
Currently, to our understanding, only the pre-season standardized fitness assessment deployed by the USFS and BLM is the Pack Test – 3 miles, at 45 pounds, with a 45 minute completion pass/fail standard on a flat course. In no way does this test adequately represent the fitness demands of wildland firefighting.
Most individual wildland fire units conduct their own early season PT training have have internal fitness assessments, but these are inconsistent and most are based on tradition and don’t match wildland firefighting’s mission-direct fitness demands – especially strength.
As well, over the years I’ve found wildland firefighter fitness cultures uneven and inconsistent. Part of this is due to the seasonal nature of most wildland fire jobs. However, given the military combat-like physical demands of wildland firefighting, and it’s danger. MTI has tried working with individal wildland fire crews to conduct our own research, but for whatever reason, it’s always fallen through at the wildland fire unit end.
I’m open to trying again, and any wildland fire crew leader or member reading this is encouraged to email me; rob@mtntactical.com.
Sources:
Ruby, B. C., Coker, R. H., Sol, J., Quindry, J., & Montain, S. J. (2023). Physiology of the Wildland Firefighter: Managing Extreme Energy Demands in Hostile, Smoky, Mountainous Environments. Comprehensive Physiology, 13, 4587-4615. DOI: 10.1002/cphy.c220016. Available online: Physiology of the Wildland Firefighter .
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Nindl, B. C., Leone, C. D., Tharion, W. J., Johnson, R. F., Castellani, J. W., & Montain, S. J. (2002). Physical performance responses during 72 h of military operational stress. Medicine & Science in Sports & Exercise, 34(11), 1814-1822.
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USFS Wildland Pack Test: https://www.fs.usda.gov/sites/default/files/2023-03/Work-Capacity-Test-brochure.pdf