White Papers

The Hidden Burn: What Firefighters Face After the Fire is Out

Reginald O'Hara022 views

Introduction

Every shift can be a matter of life or death. However, what happens to firefighters after the fire?

Picture a firefighter at the end of a high-intensity and sleepless 24-hour shift, their skin still carries the scent of smoke, their eyes heavy from exhaustion, and their heart pounding, not from adrenaline, but from constant, unrelenting stress. It’s not just the flames that wear them down. Day after day, their bodies and minds endure extreme heat, toxic smoke, collapsing structures, and traumatic emergencies. Behind courage and heroism is an often-unseen battle: the toll of chronic stress, which can have serious long-term effects on both health and performance.

A recently identified condition known as Operator Syndrome (OS) affects U.S. military Special Forces Operators (SFOs), as well as other soldiers in combat arms (Frueh et al., 2020; O’Hara et al., 2022). However, many signs and symptoms of OS are present in firefighters due to chronic wear-and-tear on the body and mind. These symptoms often go unrecognized early in a firefighter’s career, leading to potential long-term degradation in health and performance.

Dr. Christopher Frueh introduced OS in a landmark study based on a six-year observational study in U.S. military Special Forces Operators (SFOs) (Frueh et al., 2020). He recently expanded on this work in his book Operator Syndrome, which draws from his research and clinical experience with this unique military community. In the book, he includes the OS: Short Form, a tool featuring 17 key issues commonly faced by some members of the special operations community. This checklist is designed to help individuals identify potential symptoms of OS. However, Dr. Frueh emphasizes that this short form should be used alongside medical records and clinical tests for a complete evaluation (Frueh, 2024, p. 18). While created for SFOs, this tool may also be helpful for firefighters and other public safety personnel facing similar health challenges.

Operator syndrome results from a markedly high allostatic load, which is the accumulation of repeated physical and psychological stress (Frueh et al., 2020). Repeated acute stress responses (SRs) to a singular stressor (physical) immediately result in the acute dysregulation of a system (e.g., immune) (Edes et al., 2018). If adequate recovery, such as sleep, and caloric intake are applied immediately following a stressful event, systems usually return to normal functioning (Linderman et al., 2020). However, when combined with multiple stressors (e.g., physical and mental), without prompt recovery strategies, repeated SRs can result in dysregulation of one or more systems (e.g., immune and neuroendocrine) (O’Hara et al., 2022).

Ongoing physical and mental stress can lead to a wide range of interconnected health problems affecting the body, mind, and behavior in U.S. SFOs and other combat soldiers (Frueh et al., 2020; O’Hara et al., 2022; Ivory et al., 2024). Firefighters who face repeated exposure to high-stress situations often show similar symptoms. However, just like in the military, very few programs are readily available that fully address the complex health needs of firefighters.

Because of their intense and demanding jobs, elite tactical athletes, such as firefighters, SWAT officers, and emergency medical personnel, often experience overlapping health symptoms. Traditional medical approaches, which are based on average population data, do not always capture the unique and complex health challenges these individuals face. Years of repeated exposure to high-stress situations can overwork their nervous systems, leading to a buildup of strain that affects their bodies (muscles), internal systems (like organs), and mental health.

What is Allostatic Load?

Allostatic load (AL) is a way scientists explain how long-term physical and psychological stress can build up in the body over time (Frueh et al., 2020; McEwen & Stellar, 1993; McEwen, 1998–2005; McEwen., 2004; Edes et al., 2018). The idea is derived from allostasis, which means the body maintains balance by constantly adjusting to change. In simple terms, it is how the body stays stable during stress. When you face a stressful situation, real or perceived, your body kicks into gear, making rapid adjustments to meet those stress demands. This involves sending signals to the brain, activating two major stress systems: the hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal-medullary (SAM) axes.

The two critical bodily systems that respond to stress are the 1) HPA axis and the 2) SAM system (Igboanugo et al., 2023). The SAM system is fast-acting and triggers the “fight-or-flight” response, your body’s immediate reaction to danger. The HPA axis works more slowly and helps the body cope with longer-term stress by releasing stress hormones (Gonzalez et al., 2024). Although they work on different timelines and in varying ways, both systems work together to help the body adjust and stay balanced (allostasis). To do this, the body temporarily shifts energy and resources, like pulling energy from muscles, organs, and tissues, activating the immune system, and changing how digestion and reproduction function, all to handle the stressor effectively.

For firefighters, the combination of unpredictable emergencies, seasonal challenges, and everyday stress can push the body beyond its ability to cope; this is known as allostatic overload (AO) (McEwen & Stellar, 1993; McEwen, 2004). AO happens when the body spends too much energy for too long trying to deal with stress, which can wear down organs and systems. Over time, this wear and tear can accelerate aging, increase disease risk, and even early death (Bobba-Alves et al., 2022; McEwen & Wingfield, 1993).

There are two main types of AO. Type 1 AO occurs when the body does not have enough energy to meet demands, leading to weight loss, hormone imbalances, and burnout, especially when unexpected stressors hit an already drained system (McEwen & Stellar, 2003). In contrast, type 2 AO happens when the body has enough or even too much energy, often from stress-related overeating, causing it to store excess energy in unhealthy ways, which can also lead to health issues.

Ongoing stress can seriously affect firefighters’ overall health and well-being. The allostatic load/overload concept helps explain how the buildup of stress and the body’s repeated efforts to respond can lead to wear-and-tear across many body systems. While the research was not done specifically on firefighters, one study found that people with higher allostatic load levels, based on nine key health markers from the metabolic, immune, and heart systems, were more likely to experience sleep problems such as insomnia, sleep apnea, snoring, difficulty falling asleep, and shorter sleep duration (Xiaoli et al., 2014).

The Fatigue-Recovery Cycle: Why Rest Builds Resilience

When fatigue builds up over time without prompt recovery, it can lead to long-term problems. Firefighters may experience declines in physical strength, mental sharpness, hormone balance (neuroendocrine function), and immune health. Based on research with the U.S. military, we developed a theoretical model (Figure 1) that outlines the gradual steps leading to this kind of breakdown, from early signs of fatigue to under-recovery and even overtraining (O’Hara et al., 2022).

The model also shows how proper recovery after intense physical or mental strain, like a long firefighting shift or tough training, can boost performance. This is called supercompensation, when the body bounces back stronger than before. But if recovery is skipped or cut short, it can throw off the body’s internal balance (allostatic imbalance), and it may take days, weeks, or even longer to regain peak performance fully.

The good news is that fatigue and under-recovery aren’t permanent. With the proper physical and mental recovery strategies, including adequate rest, firefighters can regain peak physical and mental performance.

Figure 1. Theoretical model for allostatic imbalance continuum.

Physical, Mental, and Environmental Stressors in Firefighting

Firefighters face many physical, emotional, and environmental stressors in their line of work. Physically, they are at risk for injuries such as muscle and joint problems, either from sudden accidents like building collapses or long-term strain caused by carrying heavy gear and repeated exposure to toxic smoke and chemicals (Igboanugo et al., 2023). Most fireground injuries are caused by overexertion and strain, making up about 31% of all injuries, while slips, falls, and similar accidents account for 22% (Campbell et al., 2023). About 40% of these injuries involve muscle pain, strains, or sprains. Even more concerning are injuries sustained during training, where 57% are linked to chronic muscle problems, and 48% occur while responding to or returning from calls (Campbell et al., 2023).

Beyond the job’s physical and mental demands, firefighters often face long, irregular 24-hour shifts that can seriously disrupt their sleep. Poor sleep leads to constant fatigue and can affect memory, mood, and increase anxiety (Igboanugo, 2013). These unpredictable hours also make it hard to support a healthy balance between work and personal life (Barger et al., 2009).

Like military, firefighters work under a strict chain of command, which can sometimes create tension among team members or with leadership (Haddock et al., 2013), juggling their high-stress job with family responsibilities adds even more pressure. To keep going, firefighters push their bodies and minds to the limit, depending on a delicate balance of physical health, internal systems, and mental strength, a balance scientists call the body’s homeostatic threshold.

Better Monitoring and Support for Firefighters' Long-Term Health

Given the job’s unique physical and mental stresses, reliable tools, like surveys or lab tests, are lacking to accurately measure a firefighter’s risk of developing AO. This lack of population-specific assessment tools highlights the urgent need for long-term research to improve how firefighters’ health and performance are supported throughout their careers (Frueh et al., 2020; Ivory et al., 2024). Existing studies fall short in capturing the many complex, overlapping factors that contribute to AO, and there are very few health programs explicitly designed with firefighters in mind.

To make real progress, we need to start consistent and long-term collection of health data. This should include clinical markers, like hormone levels or signs of the immune system is functioning, to help track how a firefighter’s body is handling chronic stress over time (Frueh et al., 2020; O’Hara et al., 2022).

The body relies on several systems to handle stress and stay balanced, especially in austere environments (Seeman et al., 1997). But when stress becomes constant, these systems can get worn down, a process that can lead to AO (Seeman et al., 2001). Over time, this buildup of stress, known as AL, increases the risk of serious health problems like heart disease, weakened immunity, memory issues, and mental health conditions such as post-traumatic stress disorder (PTSD) (Frueh et al., 2020; Ivory et al., 2024). Allostatic load depicts how deeply environmental and emotional stress can impact the body’s ability to sustain health and adapt over time.

Multidimensional Recovery Tracking (MDRT) for Early Stress Detection

Firefighter health programs should consider multidimensional recovery tracking (MDRT) to better detect early signs of AL. This approach looks at both measurable data (objective) and recovery scales (subjective) to get a complete overview of how well a firefighter is adapting to physical and mental stress (O’Hara et al., 2022).

For example, objective data might include information from reliable wearable devices that track heart rate variability (HRV), sleep time and quality, physical activity, or blood tests that check for stress-related changes in the immune or metabolic systems. On the other hand, subjective data can come from quick, scientifically validated questionnaires that ask about how someone feels physically and mentally in response to stress (O’Hara et al., 2022). In some cases, due to the fluctuations in blood biomarkers over 24 hours and the associated costs, HRV monitoring could be an alternative method to assess AL. However, it requires future investigation (Corrigan et al., 2021).

A well-rounded MDRT system should cover:

  1. Real-time physical performance tracking
  2. Psychological health assessments
  3. Biological markers that monitor immune systems, respiratory, and metabolic health,
  4. Functional movement screenings to detect muscular imbalances before they lead to injury.

Experts emphasize that any tools, especially wearable tech, should be scientifically tested for accuracy, give meaningful feedback, and be easy for firefighters and healthcare teams to use (Fuller et al., 2020; Kinnunen et al., 2020; O’Hara et al., 2020).

Conclusion

Healthcare providers should consider that every firefighter is biologically unique, and their health should be assessed individually, not by using generic standards meant for the general population. This is especially important when addressing AO, the wear and tear caused by long-term stress. The first step in managing AO should be to focus on data collection methods specific to firefighters, rather than comparing them to average health benchmarks.

Health and performance monitoring should begin during a firefighter’s initial training. Collecting measurements early provides a personal baseline to track changes over time, making it easier to spot signs of physical or mental strain before they become serious. Consistent testing methods and structured systems for monitoring health data within the firefighter community should be considered to make this work.

About the Author

Dr. Reginald B. O’Hara is the Director of Applied Health and Performance at Sophic Synergistics, LLC. He focuses on improving health and performance and building stress resilience for people in high-risk jobs. He has more than 20 years of experience as a research scientist in the U.S. Department of Defense and has served as an Associate Professor and Chief Scientist at the University of Texas Health Science Center.