Physiological Stress associated with Structural Firefighting Observed in Professional Firefighters-Study



A primary goal of the project was to investigate the physical rigor of real fire scene work. Fire scene work tasks may differ widely with respect to their cardiovascular and respiratory stress. Therefore, the project sought to illustrate normative data for multiple fire ground tasks including fire attack, search & rescue, exterior ventilation, and overhaul activities.

The presence of an independent observer (scientist) on the fire ground provided opportunity to describe the fire scene environment under which firefighter physiology data was being collected. Subsequent analysis allowed the identification of the fire scene factors having the greatest impact on firefighter physiology. Further, these factors were also prioritized with respect to their relative importance.

The full access to firefighters provided by the study also allowed some investigation into the psychological aspects of answering emergency call. Specifically, a comparison of emotional stress and anxiety between on and off duty life may provide some insight in to a source of firefighter risk for development of heart disease.

Accomplishing the goals of this project required the cooperation of many organizations. A research consortium was established among the primary organizations involved. However, the ultimate responsibility for success or failure of the project lay with the individual firefighters invited to participate. It was the role of the following institutions to provide support for participating firefighters.



Indiana University Firefighter Health & Safety Research

The Firefighter Health & Safety Research program is component of Indiana University’s Harold H. Morris Human Performance Laboratory. It is governed by the Department of Kinesiology and the School of Health, Physical Education & Recreation.

The program was organized to specifically to support faculty research interests in the health and safety of First Responder populations.

The mission of Indianapolis Fire Department

Indianapolis is a rapidly growing, outstanding community that is recognized as a great place to work and live. Hailed as the 12th largest city in America and home to a diverse population, the city attracts millions of visitors annually. Indianapolis is proud to offer its citizens a world class Fire Department. IFD, with over 150 years of proud tradition, is made up of men and women with diverse cultural backgrounds, each who have taken the oath to protect and serve the citizens of Indianapolis.

Indianapolis Firefighters work closely with the residents and businesses through fire prevention and safety education programs to make their city as safe as possible. The Indianapolis Fire Department is made up of over 940 sworn members and a 50- member civilian support team. The IFD fire service district covers 198 square miles of downtown Indianapolis and surrounding areas.

With a strong history of being progressive thinking forward in areas of firefighter health and safety, IFD provided an ideal organization to participate in the study. Health status and work capacity of IFD firefighters are regularly tested. This provided a population of highly trained, medically supervised career professional firefighters.

Indianapolis Metropolitan Professional Firefighters Association

The International Association of Fire Fighters granted Indianapolis Firefighters their Charter in October of 1934. Today, Indianapolis (Marion County) and its citizens are served by 17 different fire departments are represented by Local 416. Currently Local 416 membership includes over 2,300 firefighters, paramedics, dispatchers and retirees. Local 416 fosters and encourages a high degree of skill, and efficiency, the cultivation of friendship among its members and the support of moral, intellectual and economic development of its membership. Endorsement of the project by Local 416 leadership facilitated the recruitment of firefighters for the research project. A union representative accompanied the scientific team to fire stations during recruitment. Their presence put potential subjects at ease and helped remove any suspicions or concerns the firefighters had. In addition, Local 416 worked closely with the research team to provide support


A unique aspect of the study was the need for continuous scientific observation of on-duty firefighters. IFD rotates three shifts of firefighters on a 24-hour on / 48-hour off duty cycle. To accomplish continuous monitoring, a scientist was assigned to each IFD shift. The scientist lived in the fire station and accompanied firefighters on all fire runs.

Scientists were trained in fire station etiquette and fire ground safety procedures. Scientists worked under the command of the station’s shift officer and Incident Commander at the station and on fire scenes respectively. Scientists were uniformed for identification both in the fire station and on the fire ground. Scientist uniforms distinguished them from IFD personnel but made them easily recognizable as fire ground qualified.

The study is bound by the architectural and geographical character of Indianapolis, Indiana. In order to obtain sufficient fire scene data, a highfire- volume region of the city of Indianapolis was chosen for the study site. Architecturally, this area of the city is populated by single and double wood framed residences.

Typically, these structures are less than 2000 ft2. From a geographical stand point, Indianapolis enjoys a fairly moderate climate. Accordingly, Indianapolis does not provide exposure to extremes of weather, hot or cold. The study was conducted during the winter months in order to avoid the complication of atmospheric heat stress. The goal of the study was to assess, as much as possible, the physical aspects of firefighting work. The avoidance of added heat stress provides a more focused examination on that factor. This will allow us to identify firefighter and fire scene variables impacting the physiological responses of firefighters.

Unfortunately, these delimiting factors may limit the applicability of the findings to areas outside Indianapolis or central Indiana. In order to address the impact of weather and other atmospheric extremes (elevation), a future study is planned to assess the same physiological stress on firefighters in areas of the country that will provide access to these weather extremes. In addition, US cities providing access to other architectural character will also be utilized in that future study.

Finally, the study represents physiological responses of a firefighting corps that is known to be well trained technically and monitored by a medical program adhering to NFPA standards. This group of firefighters was chosen because it may be used as a model corps. Other, less fit firefighters should not expect to respond in a similar manner.

This document reports the physiological aspects of structural firefighting and the psychological impact of answering emergency call as outlined in the associated application for funding. The use of continuous physiological monitoring to capture data required the report resulted in the capture of much information not associated with fire scenes. Every heartbeat, breath, and footstep is captured throughout the duty shift. As a result, many other aspects of firefighter physiology were captured and should be evaluated despite being outside the scope of the original project proposal. This report is limited to reporting the goals of the original funded protocol.

Other physiological issues identified during the course of the study will be pursued in subsequent peer-reviewed scientific publications. These subsequent reports will cover such topics as sleep dysfunction,

Heart rate variability analysis for determination of sympathetic / parasympathetic balance, respiratory mechanics associated with positive pressure SCBA systems, and a comparison of physical activity levels on and off duty.


It is no surprise that heart rates, minute ventilation and blood pressures are elevated during firefighting activity. The physical work demand and the emotionally charged environment require these responses. However, prior to this study, the magnitude and duration of these responses were unclear.

  • Annual reports of firefighter deaths generally list the cause of on-duty heart attack deaths as “overexertion”.
  • However, overexertion is a relative term. Levels of work that produce overexertion in one individual might not do so in another, more fit individual. Therefore, several factors must be considered to put the data presented in to context.
  • When we report means or averages of heart rates (70% of predicted HRmax) and levels of minute ventilation (50 L/min), some of the work does not seem all that strenuous.

However, firefighters studied here were highly trained, medically supervised, healthy and relatively fit individuals. The same work in a less well trained and less fit group of firefighters would result in much higher levels of cardiovascular stress.

  • In fact, work here that pushed studied firefighters to 100% of their maximum cardiovascular capacity could not be accomplished by some unhealthy and unfit firefighters.
  • Even within this group, individuals with higher levels of body fat not being able to work as hard as their leaner peers.
  • Another factor to consider is the fires themselves. The principle components analysis, the size of the structure and amount of fire involved have significant impact on the firefighter’s response. Indeed, the average structure studied was a relatively small (2500 ft2) residential structure.
  • As structures grow larger and more complex, the physical response grows. Yet, even some of these small structures pushed firefighters to their maximal abilities. Lastly, we must consider the weather conditions.

The study was conducted in the absence of ambient environmental heat stress. Unfortunately, firefighters must fight fire in all weather conditions, including hot humid weather that imposes extreme heat stress conditions on the fire scene. The process of thermoregulation can impart severe cardiovascular stress on firefighters before they set foot on the fire ground. During a 2005 study of training related physiology, a study conducted at the Maryland Fire and Rescue Institute saw many firefighters reporting for duty in a dehydrated state. Dehydration exacerbates the cardiovascular stress associated with thermoregulation and can debilitate even the most fit firefighter.


So, how does the information presented here shed light on the extraordinary number of firefighter line of duty heart attacks? The answer lies in the magnitude of the physiological responses. Recently, a comprehensive examination of the LODD due to heart attack was completed by a group at Harvard University .

  • The researchers found the primary cause of heart attack deaths associated with firefighting was overexertion in firefighters with existing cardiovascular disease.
  • A 2006 review of research on cardiac deaths indicated that high levels of physical exertion as well as severe emotional stress are triggers for a heart attack. In the case of firefighters, both physical and emotional triggers are present.
  • These researchers also concluded that periods of high physical or emotional stress essentially accelerate an inevitable cardiac event in persons with cardiovascular disease. This is an extremely important point with respect to fire fighters.
  • One of the most alarming facts with respect to on-duty firefighter heart attack fatality is the average age at the time of death is in the early 4th decade of life.
  • If you are a person with cardiovascular disease, death due to heart attack or stroke is probably inevitable.
  • However, if you are a firefighter with cardiovascular disease, that death due to heart attack or stroke is likely to come much sooner.

Another question asked about firefighter line of duty heart attack deaths is why so many occur after leaving the fire scene.

  • As discussed earlier, there is an essential physical recovery period following any physical activity.
  • The duration of the recovery period is determined by the duration and magnitude of the physical activity combined with the individual’s level of aerobic fitness (all recovery is aerobic).

This is because physical activity raises body temperature and causes the release of many hormones that enable us to do high levels of work. One of these hormones, adrenaline, is also released in response to emotional stimuli. Adrenaline raises the heart rate, blood pressure and increases minute ventilation. The higher the physical demand or emotional stress, the greater the rise in temperature as well as the amount of hormone released. These factors do not simply disappear with the cessation of physical activity or the removal of an emotional stimulus.

  • Substantial time is required to metabolize hormones and to dissipate heat. As a result, stress effects tend to linger.
  • One incident captured by the study involved the rescue of children entrapped on the second floor of a fully involved residence. The incident resulted in severe physical and emotional stress on the firefighters driving heart rates to levels in excess of 100% of their predicted maximum.

Two hours after returning to station (some three hours following the completion of rescue operations), heart rates of individuals involved in the rescue remained in excess of 100 beats per minute. Essentially, the physical and emotional triggers for heart attack stay with the firefighter for some time after an incident. High levels of stress present long after an incident, is a potential trigger for cardiovascular events, especially in individuals with underlying cardiovascular disease.


Unfortunately, many firefighters in the US are not only unfit for fire scene work but are generally unhealthy individuals. The discrepancy between the physical preparedness of firefighters and the high physical demand of firefighting stands at the center of fire service line of duty deaths. Simply to expect to survive fire ground operations, a firefighter needs, as a minimum, to be healthy (including the absence of cardiovascular disease).

The goal of this research is to support a service wide effort to reduce the number of firefighter line of duty deaths. Because heart attacks account for nearly half of these deaths, much attention is focused on elucidating and eliminating the cause of these events. Unfortunately, no substantial improvements in firefighter health have occurred in the last 25 or so years.

As a result, firefighter death statistics (as a result of heart attack) remains virtually unchanged. With improved research funding we are beginning to better understand the etiology of these events and to develop plans that will change the death statistics.

  • Currently, there appear to be two primary approaches to the problem. Some researchers are working on the development of physiology monitoring systems in hope of detecting severely elevated cardiovascular or respiratory responses during fire ground operations.
  • This in turn would allow affected firefighters to be relieved before a catastrophic event is triggered.
  • Unfortunately, the data presented here suggest this approach would not be successful. It is apparent that, in some cases, extreme physiological responses are appropriate on the fire ground.
  • Simply removing a firefighter because his or her heart rate is extremely high would stand in the way of getting the job done.

It is much more important that firefighters be healthy and fit enough to turn the output of their cardiac pumps up (increase heart rate) enough to do what they are expected to do and not experience adverse effects because of it. This seems to negate the utility of a monitoring device that simply alerts to extreme level of heart rate or ventilation.

Programs such as the Wellness/Fitness initiative undertaken by IAFF and IAFC, and the US

Fire Administration’s Life Safety Summit has recognized the need for improving the health of firefighters as a preventative measure. The national fire prevention association has issued guidelines for oversight of firefighter health programs. These programs set the stage for improvement in firefighter health. If successful, they will certainly result in a reduction in firefighter deaths due to heart attack. It is important however, that firefighters take advantage of such programs, either voluntarily or as a requirement for service.

Although there remain unknown factors on the fire ground that may increase a firefighter’s risk of developing heart disease, we know now that the vast majority of heart attack deaths occur in unhealthy, unfit firefighters. This study clearly demonstrates the magnitude of cardiovascular stress placed on working firefighters and indicates firefighting activity can be a trigger for a cardiac event. Essentially, firefighting is triggering a cardiac death that is inevitable in persons with cardiovascular disease.

So how do we stem the tide of heart attack deaths in working firefighters? We must improve firefighter health and reduce their risk factors for heart disease. Whether the responsibility for that improvement lies with the firefighter, their department or their labor organizations is for the fire service to decide.

The fire service is still asking why are firefighters dying of heart attacks and what can we do about it. Academic researchers have been demonstrating since the mid-seventies that firefighting is a substantial trigger for heart attack and preventative physical training should be required of firefighters.


Development of an effective physical training program begins with the identification of demand levels a job or event presents. Several studies have attempted to quantify the physical demand of firefighting by observation of training or simulated firefighting activity.

Unfortunately, laboratory measures tell us little about the physiology of real world structural firefighting. This was a primary reason the current study was undertaken. Adequate funding, appropriate technology, and an embedded relationship with a large metropolitan fire department enabled us to examine the physiology of real-world firefighting.

With information about the cardiovascular and respiratory demands of structural firefighting, we are now able to make statements about how firefighters should be trained. First, it is important to define what we refer to as physical fitness. The terms healthy and physically fit are not synonymous. Healthy refers to a state of well being and includes both physical and emotional aspects of life. Physical health includes not only the absence of disease but several functional physiological capabilities commonly referred to as health-related components of physical fitness.

These components include aerobic capacity, body composition, muscular strength, muscular endurance and flexibility. Sound physical training programs designed for the general population address all of these components. Programs designed for individuals who regularly endure high levels of physical stress go beyond these health-related components and include some performance-related components of physical fitness. In addition, the goals for health-related components are substantially different for these individuals compared to the general public. Athletes and firefighters fall into this higher-demand category. Sometimes you will even hear firefighters referred to as occupational athletes.

The cardiac and respiratory stress data, in combination with the inferred blood pressure responses described by this study, elucidate the firefighter’s need for a healthy cardiovascular system. The firefighter cardiovascular system will be stressed significantly, sometimes under high ambient heat stress conditions. In addition, the need to exert and maintain large muscular forces, usually from an awkward body position, indicates the need for significant muscular strength, muscular endurance, and joint flexibility compared to civilian counterparts.

Accordingly, standardized guidelines for physical training NFPA 1583, address these components for developing the firefighter’s physical fitness. As fire scene work begins, firefighters typically carry 60-70 pounds of protective clothing, breathing apparatus, and tools. As a result, little of the work executed on the fire ground could be described as having a large aerobic component. Instead, the high levels of power output required on the fire ground places emphasis on non-oxidative (anaerobic) metabolic processes. This anaerobic capacity is not considered a health-related but a performance- related component of physical fitness. An improved anaerobic capacity can significantly reduce cardiovascular stress in individuals executing anaerobic work.

Accordingly, firefighters would benefit from training that improves glycolytic and creatine phosphate metabolic system capacities. Other performance-related components of physical fitness also play a role on the fire ground. Studies conducted by Dr. Denise Smith have shown the effects of firefighting activity on the balance and coordination of firefighters. Training protocols that include agility training would also benefit the firefighter and alleviate some of the risk of trips and falls on the fire ground, a substantial origin of firefighter injury.

Lastly, it is important (from a physiological standpoint) to recognize the wide range in numbers of fires worked between fire service organizations and the effect is has firefighter physical demand.

The physiological demand required to fight a structural fire is primarily determined by the structure. Essentially, the structure sets the demand level without regard to who is coming to fight the fire (career professional, volunteer, paid volunteer etc.). As such, achieving similar goals on the fire ground places the similar physical stresses on all firefighters. However, a firefighter working in a busy company of a large metropolitan department may be required to fight multiple fires in a single shift. This lies in sharp contrast to the rural unpaid volunteer who may only work a handful of structural fires in a year.

As observed in this study, the physical stress placed on the firefighter does not simply disappear when they leave the fire scene. Significant cardiovascular stress may be present for some time following an incident. Unfortunately, this places a substantial burden on firefighters who fight large numbers of fires. These firefighters do need to be held to a higher standard of physical preparedness in order for them to recover quickly and be able to meet the demands of the next incident. Achieving a level of physical preparedness that enables the firefighter to survive and function appropriately on a fire scene should be the starting point for firefighter physical training, not the goal!

As always, the healthier and more physically fit any firefighter is, the better. However, at a minimum, the firefighter needs to a healthy and physically fit citizen. With increasing physical stress (as determined by the number and character of fires they fight), higher fitness goals need to be set to ensure the firefighter is physically prepared. This would include increased levels of all health-related fitness components and the incorporation of performance- related components into physical training programs.

In conclusion, it appears that firefighting activity presents significant cardiovascular and respiratory stress.

  • Recent evidence suggests that a majority of the cardiovascular-related line of duty deaths are caused by underlying heart disease.
  • It is clear from the data collected here that fire scene work exposes the firefighter to a substantial potential for triggering cardiovascular events. Therefore, firefighters with pre-existing cardiovascular disease exposed to the physical and emotional stress of afire scene are in extreme risk of a experiencing a myocardial infarction, stroke or other cardiovascular system collapse.
  • The fire scene is alive with many potential complicating exposure factors (toxic gases, particulates etc.) and it is certainly possible that working on a fire scene may contribute to the progression of the disease state. However, the best defense against the progression of the disease is a health monitoring plan coupled with a sound physical training program, and adequate operating procedures to lessen exposures.
  • The National Fire Protection Association has issued guidelines for such programs and, in the case of physical training program, suggests they be made mandatory.

Although this guideline meets with resistance from every faction of the fire service, departments, unions, and firefighters alike, it is a simple fact that sound physical training programs are the only way line of duty deaths due to heart attacks are going to be reduced.

Download the Indy Physiology Study – Final Report

Video Gallery

You may view or download the below videos for your personal use. Videos can be played on computers using QuickTime and on iPods. Click videos to play in a new Web browser window. Note that the videos may take time open.

Click here to download the entire video. Please note that all downloads and online playing will take time.

To download parts of the entire video, click on the individual links below. Files will play in QuickTime. If you do not have QuickTime, scroll to the bottom of the page for the QuickTime link. Also for instructions on how to download, scroll to the bottom of the page.

To watch the video from this Web page, click on the image below.

Study Video – This video shows how to assess fitness and design a training program. Videos below are listed in screen size, smallest to largest.

Fitness Assessment – Use this video to assess fitness level. Videos below are listed in screen size, smallest to largest.

Level Specific Workouts – Exercise videos for three different fitness levels. Videos below are listed in screen size, smallest to largest.

Level 1

Level 2

Level 3

Flexibility Training – Exercise video to increase flexibility. Videos below are listed in screen size, smallest to largest.

Download instructions:

To download the video files for personal use, do the following:

  1. Right-click on the file link. For example, if downloading Flexibility-240×180, your mouse pointer should be over the link and the hand should be showing.
  2. Click Save Target As…
  3. The Save As window for the computer will open.
  4. Select a folder. My Videos is a good choice.
  5. Click the Save button in the Save As window.
  6. Wait for the video to download and save to the computer.

The videos will play in the software QuickTime, a free program. To download QuickTime click here:

Filed Under: General MiscellaneousResearch HubSafety & Survival


RSSComments (0)

Trackback URL

Leave a Reply

You must be logged in to post a comment.