PHYSIOLOGICAL RESPONSES OF TRAINING OFFICERS DURING LIVE FIRE TRAINING
BY BERNARD E. WILLIAMS, Ph.D.; STEWART R. PETERSEN, Ph.D.; and KYLA DOUGLAS, M.Sc.
It has long been recognized that firefighting is one of the most physically demanding civilian occupations. This recognition has stimulated an interest in documenting the physical demands of various commonly performed job tasks1 and the development of appropriate tests for assessing firefighter fitness.2 In most jurisdictions, rigid physical fitness standards are strictly imposed when screening new recruits. Furthermore, many departments require annual testing and/or recertification to ensure that all front-line firefighters are medically and physically fit to perform their jobs.
While it is patently obvious to most observers that firefighting is a physically demanding job, it sometimes is less evident that the job of training firefighters can be equally as strenuous and physically demanding. Many front-line firefighters perceive the role of the training officer as a support function in the department, and often the view is that training staff does not require the same level of medical and physical fitness as firefighting personnel. In live fire training exercises, however, the training officer faces many of the same physical and environmental conditions as the firefighter. The training officer spends many long hours wearing bunker gear and SCBA and is required to enter burning structures to monitor trainees` performance. The training officer must also be prepared to respond quickly and conduct rescues or evacuations in cases of accidents or panicking trainees.
Several researchers have provided scientific data that quantify the physiological demands of firefighting.3,4,5 To our knowledge, however, the physiological demands of live fire training have not been scientifically examined. We began to address this concern by conducting a series of tests in which the heart-rate responses of training officers were monitored during real and simulated training exercises. This article presents the findings from a preliminary study, the first in an ongoing program of research.
Using the training grounds at the Alberta Fire Training School in Vermilion, Canada, our research team used portable heart monitors (Sport-tester PE 3000; Polar Electro, Finland) to track the heart rate (HR) response of training officers under simulated and actual training conditions. These instruments consist of a transmitter belt worn next to the skin around the chest and a “wristwatch” receiver carried in an inside pocket of the bunker jacket. The validity of these instruments has been assessed and described elsewhere in detail.6 The instruments were programmed to record HR at five-second intervals, and the data records were stored in the receiver memory during the training exercises. At the end of the exercise, the data were downloaded to a laptop computer.
HR was monitored during the following activities on two separate days: (1) preparing and igniting fires in a two-story smokehouse, (2) monitoring the activities of recruits inside the smokehouse while a live fire was in progress, (3) simulating a “person down” in the smokehouse, (4) leading attacks on “Christmas tree” and propane tanker props, and (5) demonstrating the use of a dry-chemical extinguisher on a propane fire.
Activities 1 to 3 were conducted on a winter day in early March with an ambient temperature range over the day of about 0° to 5°C (32°F to 41°F). Activities 4 and 5 were conducted in May, when the ambient temperature range was 15° to 20°C (59°F to 68°F).
Our subjects were five training officers from the City of Edmonton Emergency Response Department. Four were involved in the initial study of smokehouse evolutions. Two training officers were involved in a second set of live fire exercises involving propane props. One of the two officers in the propane exercises was not involved in the initial study. The mean age of the five officers was 42.2 years (range 37 to 46). The average length of active firefighting service was 13.2 years (range five to 20), and the average number of years as a training officer subsequent to firefighting service was 5.6 years (range one to 14).
Although an actual training class was not used in the smokehouse scenarios, the researchers posed as recruits and entered the smokehouse under live fire conditions. The heart rates of the training officers were continuously assessed under three distinct conditions: hauling material and building the fires in the smokehouse (setup); igniting the fires and escorting the researchers through the building (training); and monitoring the training simulation from outside the building (safety).
All four training officers participated in constructing and igniting fires using wood, straw, and diesel fuel as they normally would in preparing for a training exercise. They then exited the smokehouse and allowed time for the fires to burn and fill the smokehouse with heat and smoke. Two training officers then reentered the smokehouse and positioned themselves so they could watch the researchers, posing as recruits, as they entered the smokehouse.
During these procedures, the other two training officers remained outside as safety officers. Two separate evolutions were conducted to allow each training officer the opportunity to serve in each role. Without the training officers` previous knowledge, the researchers simulated an accident during the second evolution. The safety officers were called to initiate a rescue.
The propane exercises were conducted with a class of 16 City of Edmonton firefighters involved in a hazardous-materials second-responder training program. During these exercises, the heart-rate responses of the two instructors and a sample of the students were monitored. All the students in this training group were experienced firefighters.
Monitoring took place during two different series of drills. The first series involved a controlled attack with four handlines on different propane props, including a Christmas tree and a simulated tank. In these drills, the two training officers took the lead role on the attack line or a support role on a safety line.
The second series involved a propane impingement fire. In this drill, the training officers demonstrated the technique for extinguishing a propane fire with a dry-chemical extinguisher. Following the demonstration by the instructor, the students completed the drill individually. For purposes of comparison, four firefighters` heart rates were monitored along with those of the training officers.
During all exercises, participants wore NFPA 1500 (Standard on Fire Department Occupational Safety and Health Pro-gram–1992)-compliant protective clothing including bunker boots, bunker pants, bunker coat, Nomex® flash hood, helmet, gloves, and Scott 4.5 SCBA including face piece. During the setup phase of the smokehouse exercise, the training officers did not wear SCBA. All participants used air as required during the various phases of the other activities, as would normally be appropriate. For example, the training officer did not use SCBA while providing instructions and organizing the next group of trainees for brief periods between evolutions on the propane tank simulation.
Results of the tests are shown in Figures 1 through 5 on page 49.
The results of this research clearly indicate that training officers experience significant increases in heart rate when conducting routine live burn exercises. On each heart-rate record (Figures 1 to 5), the predicted maximum heart rate is shown as a group average (Figures 1 and 2) or for the individual training officer (Figures 3 to 5). The prediction of maximal heart rate was based on the well-accepted age-related method of 220 bpm minus age in years.
It is interesting to note that in two of the five exercises, the physical, emotional, and environmental stress on the training officers resulted in heart rates that approached or exceeded the predicted maximal value. The comparisons of heart rate response of training officers and firefighters during propane drills indicate that the training officers actually experienced higher heart rates than the firefighters. One possible explanation for this is that the responsibility associated with the position subjects training officers to additional stress.
Other research has indicated that psychoemotional stress results in high heart rates consistent with vigorous exercise. High heart rates have been documented in medical students presenting at grand rounds, officials in basketball, hockey and basketball coaches, and race-car drivers7,8,9,10 in the absence of vigorous exercise. It is possible to distinguish between the source of the “stress” (i.e., psychoemotional or physical) and even estimate the relative contribution of each to the cardiovascular response if appropriate biochemical stress markers are measured in the blood and urine. However, such invasive parameters were beyond the scope of the present pilot study.
It is well accepted that psychoemotional stress promotes atherosclerosis and coronary heart disease through the effects of catecholamines (e.g., epinepherine and norepinepherine). It has been shown that increased physical fitness attenuates the catecholamine release during stressful situa-tions11 and that physical training also decreases the catecholamine response to exercise.12 Schwaberger found significant negative correlations between heart rate and catecholamine excretion during race-car driving and measures of physical fitness. These data suggest a strong protective effect of physical fitness in the management of acute and chronic stress.
While this study measured heart-rate response only, there were visible signs that the training officers were experiencing other physiological stresses–for example, there was evidence of profuse sweating, indicating that heat stress was likely being experienced. In previous research that measured core body and skin temperatures, it was discovered that subjects wearing bunker gear experienced significant rises in body temperature during and following exercise.13 These previous tests were conducted in laboratory conditions at normal room temperature, and it was suggested that the results likely would be more pronounced in a hot and hostile environment.14 In the present study, the tests were conducted in a hot and hostile environment. The smokehouse was fully charged with black smoke, and temperatures were estimated to be in the range of 500° to 800°F.
The rise in heart rate experienced by the training officers in this study likely was accompanied by other physiological re-sponses, such as increased body temperature, increased oxygen consumption, and increased blood pressure. These are normal physiological responses that can be handled by medically and physically fit individuals. Persons not medically and physically fit, however, would be putting themselves and others at considerable risk by participating in activities of this nature.
The sudden rise in heart rate the safety officer experienced when there was a report of a “person down” in the smokehouse demonstrates that a psychological stimulus can have as dramatic an effect on heart rate as a physiological stimulus. This sharp increase in heart rate also suggests that all training staff on-site during live burn exercises, even those in safety or support roles, must be medically and physically fit and prepared to leap into action if required.
In this study, the physiological demands on training officers were found to be similar to, and in some cases in excess of, the physiological demands on firefighters. The most obvious implication of these results is that the medical and physical fitness standards for training officers should be similar to those for front-line firefighters. In some departments, training officer positions are filled by aging or injured firefighters deemed unfit for front-line duties. This may be an acceptable practice, provided that these individuals are used exclusively for classroom instruction. However, any training officer involved in live fire training, even in a backup position or safety officer role, should meet the medical and physical fitness standards established under NFPA 1582, Medical Requirements for Firefighters.
Observations of increased heart rate and profuse sweating during smokehouse exercises suggest the need for training officers to take regular rest breaks, as firefighters do. During rest breaks, a concerted effort should be made to consume fluids to rehydrate and cool the body. Previous research has demonstrated that the insulative properties of bunker gear decrease the body`s ability to dissipate heat. As a result, body temperature continues to rise following exercise.15,16 This suggests that during rest periods between training evolutions, training officers and trainees should remove helmets, flash hoods, bunker coats, and bunker pants to allow the body to properly cool down. Since physical activity levels were relatively moderate and did not change significantly in our study, we suggest the pattern of increasing heart rate during smokehouse evolutions is likely due to accumulated heat exposure. Although our data do not permit complete investigation of this observation, it seems a plausible explanation.
In typical live fire training scenarios, particularly those involving new recruits, many series of evolutions are conducted during each training session. Training officers may be involved in dozens of evolutions during a single day. Given the physiological stresses experienced by training officers in this study, it is vital that training officers be in top medical and physical condition and that they take appropriate steps to ensure they are properly hydrated and cooled down between evolutions.
As noted in the introduction, the purpose of this article is to provide the results of a preliminary study, which has several limitations–smokehouse evolutions in this study were simulated, with researchers posing as recruits; and only two evolutions were conducted. Heart-rate responses of the training officers were measured, but there were signs that other physiological responses relating to heat stress should be examined. The findings clearly suggest a need for further research.
In future research, we propose to examine training officers` cardiovascular responses during several full days of actual training exercises with recruits. Further, we propose to examine other elements of physiological and psychoemotional stress such as body temperature, fluid loss, plasma lactate, free fatty acids, and concentrations of catecholamine excretions. The results of this research will be reported in future articles.
The authors express their gratitude to the training officers and members of the Dangerous Goods Response Team with the City of Edmonton Emergency Response Department, who demonstrated a high level of dedication and professionalism through their cooperation and participation as subjects in this research project.
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The heat, smoke, and fire encountered in live fire training make physical demands on trainers and trainees similar to those of actual firefighting. (Photos by Shean Kubiski.)
Evolutions in the Alberta Fire Training School simulated training exercise included (top) extinguishing a “Christmas-tree” propane fire (photo by Gerry Emas) and (bottom) putting out a fire with a dry-chemical extinguisher (photo by Kyla Douglas).
Training officer lights fire in smokehouse. (Photo by Gerry Emas.)
BERNARD E. WILLIAMS, Ph.D., is deputy chief of the City of Edmonton (Canada) Emergency Response Department. He has served in the fire service for more than 16 years and is an adjunct instructor at the National Fire Academy in Emmitsburg, Maryland.
STEWART R. PETERSEN, Ph.D., is an exercise physiologist and associate professor in the Department of Physical Education and Sport Studies at the University of Alberta, Edmonton, Canada. He has been involved in developing physical fitness testing protocols and job-related testing procedures for firefighter recruit candidates and has also developed physical fitness training programs for firefighters.
KYLA DOUGLAS, M.Sc., is a graduate student in the Department of Physical Education and Sport Studies at the University of Alberta, Edmonton, Canada. She has extensive experience in testing firefighter recruit candidates and monitoring heart-rate responses in college athletes during competitive sporting events.