Physical Capabilities of Instructors at the End of Hot Fire Training (0305) [158529]

8/2/2019 Physical Capabilities of Instructors at the End of Hot Fire Training (0305) [158529]

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5/2003: Physical Capabilities of Instructorsat the End of Hot Fire Training


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On 5th May 2006 the responsibilities of the Office of the Deputy Prime Minister (ODPM) transferred to the Department forCommunities and Local Government.

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The findings and recommendations in this report are those of the consultant authors and donot necessarily represent the views or proposed policies of Communities and LocalGovernment.

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Contents

Front page

Abstract

Management summary

1. Introduction

2. Questionnaire

3. Methods

4. Results

5. Discussion

6. Conclusions

7. Recommendations

Acknowledgements

References
http://index.asp/?id=1125250#P654_75415http://index.asp/?id=1125249#P651_74842http://index.asp/?id=1125248#P643_71409http://index.asp/?id=1125247#P634_70065http://index.asp/?id=1125246#P605_49260http://index.asp/?id=1125245#P321_35785http://index.asp/?id=1125244#P269_20835http://index.asp/?id=1125243#P108_13161http://index.asp/?id=1125242#P100_5458http://index.asp/?id=1125241#P34_2002http://index.asp/?id=1125240#P31_979http://index.asp/?id=1125239#P21_257


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Go to table of contents

Front page

Firefighter training: Determination of the physical capabilities of instructors at the endof hot fire training exercises

byDr Clare Elgin & Prof Michael TiptonDepartment of Sport and Exercise ScienceUniversity of Portsmouth

The text of this publication may not be reproduced, nor may talks or lectures based on thematerial contained within the document be given without the written consent of the Head of theFire Research Division.

The views expressed by the authors of this report do not necessarily reflect those of the

Office of the Deputy Prime MinisterResearch report number 5/2003

Office of the Deputy Prime MinisterFire Research DivisionPortland House, Zone 18/DStag PlaceLondon,SW1E 5LT

Crown copyright


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Abstract

The aim of this study was to determine whether fire-fighter instructors are capable ofperforming a simulated rescue task after undertaking a live fire training exercise. Teninstructors performed a rescue task on 2 occasions, the first acted as a control and was

conducted when they were euhydrated and normothermic. The second task was undertaken10 min after a live fire-fighting training exercise resulting in an average deep body temperatureof 38.1C. All instructors were able to successfully complete both rescue tasks though heartrate and rating of perceived exertion were higher after the training exercise. In a second study,6 out of 7 instructors were able to fully complete a rescue task conducted 79 s after a trainingexercise that increased deep body temperature to 38.3C. Although most of the instructorswere able to perform a rescue task after the live fire training exercise, they were close to theirphysiological limit and therefore in more severe situations a rescue may not be possible.


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Management summary

High deep body temperatures and heart rates have been observed in fire-fighter instructors atthe end of some live fire training exercises suggesting their ability to perform a rescue may becompromised. The aim of this study was to determine whether fire-fighter instructors are

capable of performing a simulated rescue task after undertaking a "Hot Fire" training exercise.A questionnaire was sent to all the UK Fire Service brigades to determine the worst casescenario for rescuing a collapsed fire-fighter. 89% of brigades responded, and withconsultation from the instructors at the Fire Service College a representative rescue task wasdevised.

Ten fire-fighter instructors undertook 2 simulated rescues, which involved dragging a 80.6 kgdummy 23 m along the flat and down 2 flights of stairs. Prior to the first rescue (Rcontrol), theinstructors had not been exposed to heat within the previous 12 hr. The second rescue (Rhot)was undertaken approximately 10 min after they had acted as a safety officer in a Hot Fire

training exercise (HF1) lasting about 40 min. In a second study, 7 fire-fighter instructorsundertook a simulated rescue (Rflat) involving dragging a 85 kg dummy 30 m along the flat,approximately 79 s after being in a Hot Fire exercise (HF2) lasting on average 41 min.Throughout the Hot Fire exercises and rescue tasks the instructors wore their full protectiveclothing and self contained breathing apparatus.

All the instructors were able to complete Rcontrol and Rhot. Six out of the 7 instructors wereable to complete Rflat, the instructor who did not complete Rflat was able to drag the dummy20 m. Results are shown in Table 1 and 2.

HF 1 HF 2

End rectal temperature (C) 38.1 0.4 38.3 0.7Mean HR (bpm) 131 18 121 20Fluid loss (L) 1.48 0.70 0.89 0.29

Table 1. Physiological responses to the Hot Fire training exercises

Variable Rc Rhf RflatBefore HR (bpm) 75 9 110 25 * 129 32

Rating of Perceived Exertion 6.5 0.9 12.1 1.8 *Perceived inability to perform rescue 0.6 1.0 3.5 1.7 * 4.1 1.5

During Rescue time (s) 90.1 28.6 78.7 15.6 41.7 6.9Max HR (bpm) 162 16 180 15 * 182 20

After Rating of Perceived Exertion 13.3 2.4 15.7 2.1* 16.3 2.4Lactate (mmol.L -1) 5.84 2.79 6.08 1.76 8.3 1.9

Table 2. Physiological responses during rescue tasks. Statistical comparison was only madebetween Rc and Rhf, and asterix indicates a significant difference between Rc and Rhf.

The instructors were able to complete a rescue task (Rhot) simulating a worst case scenario atthe end of a Hot Fire exercise, however they experienced a greater physical strain during Rhotcompared to Rcontrol. The 10 min period between HF1 and Rhot may have been crucial inenabling the instructors to recover and perform the rescue task. When the rest period was


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reduced to 79 s (Rflat), 6 out of 7 instructors were able to drag the dummy the full 30 m. Theinstructor, who could not complete the full 30 m dummy drag, was one of the less fitinstructors.

Within the limits of the current study, instructors are capable of performing a rescue at the endof a Hot Fire exercise. However, the rescue tasks resulted in near maximal HR suggesting theyprobably had very little spare physical capacity. Therefore in less favourable situations (higherdeep body temperatures, greater levels of dehydration, less fit or experienced instructors, or acasualty heavier than 85 kg) a rescue may not be possible.


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1. Introduction

Fire-fighters can be exposed to severe toxic and thermal environments during their normalduties. During "Hot Fire" training exercises, air temperatures around the fire-fighter are typically100C to 170C with peak temperatures up to 235C (Foster and Roberts 1994; Eglin and

Tipton 2000). Burns occur when the skin temperature is elevated to 44C and the severity ofthe burn increases logarithmically with increasing skin temperature and duration of exposure(Ripple et al. 1990). Therefore, protective clothing and self-contained breathing apparatus(SCBA) are essential in order to protect fire-fighters from severe environmental conditions.However, the protective clothing worn by a fire-fighter not only acts as a barrier to externalheat, it also impairs heat loss from the body. Fire protective clothing is relatively impermeableto water vapour (Pascoe et al. 1994; Goldman et al. 1990) and therefore inhibits evaporation ofsweat which is the only method of heat dissipation from the body in a hot environment. Thisresults in a greater increase deep body temperature during exercise when protective fire-fighting clothing is worn compared to normal work uniform (Duncan et al. 1979; Faff and Tutak1989; Smith et al. 1995; Skoldstrom 1987; White and Hodous 1987). In addition, the weight of

the protective clothing and SCBA also represents a physiological burden. This increases themetabolic cost of any given task (Duggan 1988; Duncan et al. 1979), and thus the amount ofheat produced. This may be compounded by the "hobbling" or encumbering effect of the bulkyclothing (Duggan 1988; Goldman 1990; Home Office 1996; Patton et al. 1995). For anyactivity, this added metabolic cost decreases the time to fatigue and heat illness (Louhevaaraet al. 1995).

Fire-fighting involves strenuous physical activity (Lemon and Hermiston 1977; Romet and Frim1987). The level of activity required depends on the task undertaken during the fire-fightingscenario and the role of the individual (Romet and Frim 1987). During fire-fighting scenarios ata fire ground, Romet and Frim (1987) reported that search and rescue tasks were the most

demanding, resulting in heart rates above 150 beats.min-1

and increases in deep bodytemperature of 1.3C in the "leading hand". Less physiological demand was placed on theother members of the fire-fighting team. Performing a simulated ceiling overhaul task in theheat (90C) for 16 min resulted in an average heart rate of 175 beats.min -1 corresponding toapproximately 90% of the age-predicted maximum. At the end of this exercise deep bodytemperature, measured using an infrared tympanic thermometer, averaged 39.82C (Smith etal. 1997). In drills comprising of sets of fire-fighting tasks conducted in a building containingfires, heart rates above 180 beats.min -1 and increases in tympanic membrane temperature of1.5C have been observed (Smith and Petruzzello 1998). Similarly, during simulated smokedives in the heat, near maximal and maximal heart rates were recorded in young, very fit, fire-fighters (Lusa et al. 1993). During a real fire situation, a heart rate of over 160 beats.min -1 for90 min was recorded in a fire-fighter during 2 consecutive fires, and whilst fire-fighting for 15min averaged 188 beats.min -1 (Barnard and Duncan 1975). These studies show thatconsiderable physiological strain can be placed on an individual performing fire-fighting tasks.

Few studies have examined the responses of instructors during Hot Fire exercises. Onepreliminary study investigated the responses of fire-fighter training officers during real andsimulated training exercises (Williams et al. 1996). The heart rate of four instructors wasmonitored during five different training exercises. During two of the five exercises, the trainingofficers experienced heart rates that approached or exceeded their age-predicted maximumand were higher than the heart rates of trainee fire-fighters. Under the contract "Physiological


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monitoring of fire-fighters during training" the authors monitored 13 Breathing ApparatusInstructors during 44 live fire training exercises at the Fire Service College (FSC), Moreton-in-Marsh (Eglin and Tipton 2000). The physiological responses of the instructors to the exercisesvaried considerably due to differences in the heat loading and physical activity. At the end ofthe exercises, the deep body temperature of the instructors averaged 38.5C; in 8 exercises itexceeded 39C. Maximum heart rate during the exercises averaged only 138 beats.min -1,however, in 5 exercises it exceeded 90% of the individual's heart rate reserve. Thus during aproportion of the training exercises the instructors experienced considerable physiologicalstrain and two instructors showed signs of heat stress, viz. nausea and dizziness.

The combined effect of heat and physical exertion can impair physical and mentalperformance. To gauge whether any performance decrement might have occurred, theinstructors were asked whether they thought they could perform a rescue at the end of thetraining exercise. Although all the instructors believed they would have had no problemsperforming a rescue after live fire training exercises conducted in modified containers, this wasnot the case for those conducted in the fire buildings ("Hot Fire" exercises). After 3 (out of 20exercises involving 12 different instructors) of these exercises, the instructor doubted his abilityto perform a rescue, and 1 instructor was sure he would not be capable. As the key function ofthe instructors is to act as safety officers during the training exercises, and hence beresponsible for rescuing a collapsed trainee fire-fighter, these findings were cause for concern.

In an extension of this study, we measured the energy demand of rescuing a 50 kg dummywearing SCBA from a fire building. Even though the dummy was considerably lighter than theaverage fire-fighter, there was no heat exposure and the instructors were assisted, thesimulated rescues required heart rates of 160 bpm and an average energy expenditure of 47kcal. If no heat was dissipated, this would result in an increase in deep body temperature of0.6C. Given the highest deep body temperature at the end of a Hot Fire exercise was 40.6Cand heart rates up to 194 beats.min -1 were observed, it was concluded that the ability toperform a rescue at the end of an exercise may be severely compromised.

There have been no studies that have examined the ability to perform a rescue after beingexposed to the severe environmental conditions experienced during fire-fighter trainingexercises. The worst case scenario would involve an instructor having to rescue a student fire-fighter at the end of an arduous training exercise. The aim of this study was to determine thephysical capabilities of instructors at the end of a live fire training exercises (Hot Fire exercise),to establish whether they can be reasonably expected to perform such a task. To ensure thestudy was relevant to the fire-fighting training establishments throughout the UK, aquestionnaire was sent to all the UK Fire Service brigades. From the responses to thesequestionnaires, and through consultation with the instructors at the FSC, a typical "worst casescenario" rescue task was developed. The ability of instructors to perform this rescue task wasexamined when fresh (euhydrated and normothermic) and after acting as a safety officer in alive fire training exercise. It was hypothesised that the physical demand of performing therescue task after heat exposure would be greater than the control rescue to the point ofpreventing a rescue from being completed.


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2. Questionnaire

2.1 Introduction

Prior to any of the field testing, a questionnaire (Appendix A) was sent out to all of the UK FireService brigades (n=54), the aim being to inform the protocol for the rescue task and ensurethat it was relevant to the brigades. The questionnaire asked whether training exercisesinvolving exposure to fire or heat were conducted at the brigades' training facility and the staffto student ratio on these exercises. Information on procedures, risk assessments and methodsfor casualty evacuation, the furthest distance a casualty may have to moved to safety and themajor obstacles to be negotiated during a rescue were requested. The brigades were alsoasked to say how many rescues they had performed during a training exercise in the previous2 years (1999 to 2001), and what issues had arisen as a consequence. In addition, they wereasked to give details of any health surveillance or fitness assessments conducted on theirinstructors/safety officers.

48 brigades completed the questionnaire (response rate of 89%), 47 of which conduct theirown fire training exercises involving exposure to heat. The training exercises conducted by thebrigades are shown in Table 2.1.

Training Exercise Number of Brigades Staff : student ratio

(mean sd)Live flame / fire 43 0.36 0.16Heat 40 0.32 0.10Heat and humidity 30 0.32 0.08

Table 2.1. Number of brigades undertaking fire-fighting training exercises involving exposureto heat and the staff student ratio on those exercises (n=48).

Risk assessments have been carried out for the training exercises conducted in all but twobrigades, one of which is currently in the process of writing them. The procedures forevacuation of the training facilities are fully documented in most brigades, however the bestroute for evacuation of a casualty usually forms part of the safety brief rather than beingdocumented (Table 2.2). In all cases, the method of casualty evacuation was manual, a fewbrigades reported they may use stretchers or trolleys. One training facility has a lift in some firehouses, and use of a hydraulic platform for recovery of a casualty, otherwise no mechanicalaids are used to assist recovery.

Documentation Training FacilityEvacuation

Casualty EvacuationRoute

Fully documented 28 13Part of safety brief 19 25Fully documented & part of safetybrief

3 1

No documentation 3 10Table 2.2. Number of brigades that document the procedures for evacuation of the training


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facility and the best routes of casualty evacuation (n=48).

In every brigade an instructor or safety officer performing a rescue would have help from eitheranother instructor (n=19), a student (n=2) or both (n= 26). In the worst case scenario, thefurthest distance a casualty may have to be moved to safety was reported to average 9.8 6.7m (range 3.5 to 30 m). The furthest distance that one person may have to move a casualtyaveraged 5.9 3.5 m (range 1.5 to 15 m), however, 17 brigades reported that this was notapplicable and that an instructor would never have to move a casualty unaided. The numberand type of obstacles that may hinder a casualty rescue varied between training facilities,however the most common was stairs (Table 2.3).

Obstructions Indoors OutdoorsDoors 13Stairs 32 28Ladders 7 5Crawl ways 3Hatch ways or equivalent 3 2

Partitions 4Confined spaces 3Furniture 6Gangways 1

Table 2.3. Number of brigades that have obstructions inside and outside their fire trainingfacility, and the nature of those obstructions (n=48).

Nine brigades reported that a fire fighter had collapsed in the past 2 years at their trainingfacility. The details of the collapses and the control issues that were subsequently put in placeto prevent another occurrence are shown in Table 2.4.

BrigadeID Numbercollapsed Cause of collapse Control measures

1 1 Not specified No change required, followedpredetermined plan

2 1 Heat exhaustion Reduced the temperature andexposure time

5 2 Cylinder valve not turnedon enough

Specific brief to ensure that it isturned on - buddy system in place

11 2 Not specified Health and Safety investigationongoing

13 1 Heat exhaustion attributedto hypoglycaemia

Dietary advice included in safetybrief

14 2 Ill health Rescues completed satisfactorily &according to plan

25 1 Illness exacerbated byalcohol consumption

Reviewed documentation on fluidconsumption.

28 2 Not specified New management systems put inplace

48 3 Heat exhaustion Procedures proved effective,ambient temperature closely


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consideredTable 2.4. Incidence of collapsed students in training facilities in the past 2 years (1999 to2001). The cause of collapse and any control measures put in place to avoid the problemrecurring are also detailed.

The method of assessing fitness for work before an individual is assigned the role of aninstructor or safety officer, and the health surveillance of those already in this role variesconsiderably between brigades. The prevalence of the methods employed by the brigades forassessing fitness and health are shown in Table 2.5. Notably only one brigade reportedmeasuring core temperature (using an aural thermometer) after every exposure.

Method Fitness assessment Health surveillanceQuestionnaire 2Medical 21 7Fitness test 9 2Occupational Health Department initiative 23Training centre initiative 15

Self assessment 2Log books 4Core temperature monitoring 1Other 1 1None 13 6Not answered 4 2

Table 2.5. Number of brigades that assess fitness to work before an individual is assigned therole of an instructor/safety officer and the methods used. Also shown is the number of brigadesthat undertake health surveillance on instructor/safety officers and how this is conducted.

2.2 Development of the rescue taskThe responses to the questionnaire indicated that an instructor/safety officer would be helpedby another instructor or student. The furthest distance a collapsed individual may have to bedragged to safety was 30 m, though 15 m was the maximum one person may have to move acasualty. The major obstructions to a rescue were stairs, doors, ladders and furniture (Table2.3). Based on this information, a worst case rescue task scenario was devised in consultationwith instructors from the FSC.

It was decided that the rescue would be performed in the cold side of the BA School as it is a"typical" fire house and would be available throughout the trial, thus enabling the rescue task toremain constant for each individual. For this particular building, the instructors determined thatthe worst case scenario for rescuing a victim would be if they collapsed by the door separatingthe cold and hot side of the building on the second floor (effectively in the middle of the buildingfurthest away from an exit). An individual who collapsed here would have to be moved along acorridor (approximately 15 m) to fresh air and then down 2 flights of stairs to clear the building.The width of the corridor (0.95 m) was too narrow to enable 2 instructors to drag a victim andthe only way 2 people could actively participate in the rescue would be to carry the casualty.This was considered more demanding than having one person drag the victim on their own,and in a real situation they decided that one instructor would do the drag and have otherinstructors available to take over should they become fatigued. Having the instructor conduct


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the rescue on their own also negated the problem of determining the contribution of effort putin by the instructor who was being monitored and ensuring that this was kept constant for allrescues. Thus, it was concluded that the rescue task would involve a single person drag of adummy representative of the weight of a fire-fighter along a 15 m corridor and down 2 flights ofstairs.


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3. Methods

3.1 Introduction

The experimental protocol was approved by the University of Portsmouth ethics committee.Thirteen fire-fighting instructors from the Fire Service College (FSC) Moreton-in-Marsh actedas subjects for the trials detailed below after giving informed written consent. All experimentswere conducted in the fire grounds of the FSC, Moreton-in-Marsh.

3.2 Simulated rescue task

3.2.1 General

Ten instructors performed 2 simulated rescues of a 80.6 kg dummy (including the mass of theSCBA strapped to dummy) in a cool smoke-free environment. The first rescue acted as acontrol and was performed when the instructors had not been exposed to heat in the previous12 hours (Rcontrol). The second rescue was performed after the instructors had been exposedto the heat during a live fire-fighter training exercise (Rhot). Both Rcontrol and Rhot wereconducted in the cold side of the BA School.

During the Rcontrol, the instructors wore their normal full protective clothing and a Metamaxrespiratory mask and a rucksack weighing 11 kg which replaced and simulated their breathingapparatus set. During the Rhot, the instructors wore the same clothing as they had in the HotFire exercise with either their SCBA or the weighted rucksack containing the Metamax. Therescue task was only conducted if the instructor was happy to do so (i.e. the rating of theirability to perform a rescue was less than 7 - see below) and they had a rectal temperaturebelow 39.5C (only measured during Rhot).

Figure 3.1 Instructor performing simulated rescue task (Rcontrol). The instructor has draggedthe dummy along a corridor and down 2 flights of stairs and has a further 8 m to drag thedummy. The instructor is wearing a RUCs containing the Metamax system for measuringoxygen consumption which has been weighted the same as the SCBA.


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After measurement of resting oxygen consumption (Rcontrol) or arrival from the Hot Fireexercise (Rhot), the instructor walked up 2 flights of stairs to where the dummy was located.The rescue involved turning the dummy 180 in a corridor 0.95 m wide and then dragging italong a flat corridor for 14.8 m to reach the stairs. There were 2 obstructions in the corridor - adoor they had to push open and a fire hose which reduced the width of the corridor to 0.63 m.The instructors then dragged the dummy down 2 flights of stairs (8 steps per half flight 0.18 mheight, width 1.04 m, total vertical height 5.8 m) and then 8 m along level tarmac to the finish.Throughout the rescue, the instructor was guided by another firefighter who ensured they didnot trip, but who did not give any physical assistance in dragging the dummy (Figure 3.1). Thetime taken to complete the rescue was measured from the point at which the instructorreached the dummy.

3.2.2 Measurements during Rcontrol and Rhot

Oxygen consumption ( V O2) was measured using a portable measuring system (Metamax,Cortex Biophysik) during all of the Rcontrols and 6 Rhots. V O2 was recorded every 20 s duringa 5 min rest period (prior to Rcontrol only), throughout the rescue and 15 min of recovery.During both rescues heart rate was recorded at least every 15 s using a Polar heart rate

monitor (Polar Electro Oy, Kempele, Finland). Blood lactate was measured from a finger pricksample of blood taken before and 2 min after both rescues using a portable hand held lactateanalyser (Lactate Pro, Arkray Inc, Kyoto, Japan). Rating of perceived exertion (RPE, a 15 pointscale from 6 to 20, modified from Borg 1970) was obtained before and immediately after bothrescues. The instructors were also asked to rate their ability to perform the rescue on a scaleof 0 to 7 (0 being easily, 7 being impossible) prior to both rescues.

Total metabolic demand of the rescue task was calculated from the total V O2 (L) measuredduring the rescue task and recovery minus resting V O2 (L) over the same time period. InRcontrol resting V O2 was calculated from the average of at least 3 min during the restingperiod. Since in Rhot there was no resting period, the lowest V O2 prior to the rescue task was

taken as the resting V O2. Total aerobic demand was defined as the total V O2 (L) measuredduring the rescue task above resting levels. Total anaerobic demand was defined as the totalV O2 (L) during recovery above resting levels; it was assumed that this was representative ofthe oxygen consumption that could not be met aerobically during the rescue task (Bilzon et al.2001).

3.3 Hot fire exercise

3.3.1 General

Ten instructors were monitored during live fire-fighter training exercises (Hot Fire exercises) in

which they acted as safety officers. Every effort was made to try and ensure that thephysiological monitoring did not interfere with the work conducted by the instructor. Thereforeno restrictions were made on food or drink before the testing period other than the standardrecommendation that they should try and be fully hydrated prior to the exercise.

The Hot Fire exercises were conducted in one of the purpose built fire houses within the FSC -either the BA School (n=6), Ship (n=2), Commercial (n=1) or Domestic (n=1) buildings. The fireand smoke bale loading for the Hot Fire exercises varied between buildings and exercises. Insome cases the instructors were assigned to the same floor, but more often, they were ondifferent levels. During the Hot Fire exercise, the instructors' principle task was to monitor the


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progress of the students conducting search and rescue tasks and fighting the fires, and also toprovide safety cover should it be required. There were no incidents requiring the instructors (orany other safety officer) to perform a rescue in the exercises monitored during this study.Throughout the exercise the instructors positioned themselves in the coolest areas thatenabled them to observe the student fire-fighters. During a few exercises, when no studentswere on their floor of the building the instructors rested outside.

Prior to the Hot Fire exercise (either just before or just after the exercise briefing) theinstructors provided a urine sample, were weighed in minimal clothing and then instrumentedwith the physiological monitoring equipment (section 3.2.1). Once fully dressed in their fire-fighting ensemble (section 3.4) the instructors went out to the fire ground where the exercisewas being conducted. The instructors were asked to behave during the exercise as if theywere not being monitored and not try to get hot or avoid the heat more than they wouldnormally. During the exercise the instructors were asked to report by radio when they changedtheir position or activity within the building. They were also asked to give a discomfort rating atleast every 10 min or when their level of comfort changed. A rating of 1 to 7 was used with 1being comfortable and 7 being unbearably uncomfortable.

At the end of the Hot Fire exercise the instructors performed the simulated rescue which wasalways conducted in the BA School. When the Hot Fire exercise was conducted at anotherlocation they were driven to the start of the rescue. The time lapse between the end of the HotFire exercise and the rescue varied depending on the location of the Hot Fire Exercise, theaverage time being 10.4 3.3 min (range 6 to 21 min).

At the end of the Hot Fire exercise and Rhot the instructors were weighed in minimal clothingfor measurement of sweat loss. They also filled in a questionnaire (Appendix B) about the HotFire exercise they had just performed. In the questionnaire they were asked to indicate how hotand demanding they thought the exercise was by marking a 100 mm line. A mark at 0 mmcorresponded to an exercise which was not hot/demanding; at 50 mm it corresponded to anexercise of average heat/demand and 100 mm to an exercise that was very hot/demanding.They were also asked when their last heat exposure had been and what exercise they hadtaken in the last 24 hours.

3.3.2 Variables Monitored

Environmental Temperature

Environmental temperature was measured on the outside of the instructors' tunic using athermocouple (Type K, Grants Instruments, Cambridge, UK) secured at the level of theshoulder. The temperature was recorded every 1 min on the data logger (modified Squirrel

1000 series, Eltek, Cambridge, UK) worn under the tunic.Environmental temperature was also measured in the buildings using thermocouples attachedto a metal pole positioned at 0.3, 0.6, 0.9, 1.2, 1.5 and 1.8 m from the ground. The"thermocouple tree" was placed where the instructors would spend most of their time duringthe exercise (i.e. away from the direct heat of the fire but with a good view of the route thestudents would take), without being in their way or causing a tripping hazard for the studentfire-fighters. The temperatures were recorded every 1 min on a data logger (Squirrel 1200series, Grants Instruments, Cambridge, UK) placed in a insulated box.


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Deep body temperature

Deep body temperature was measured using a rectal thermistor (Grants Instruments,Cambridge, UK) inserted 0.15 m beyond the anal sphincter and recorded every 1 min on thedata logger (modified Squirrel 1000 series, Eltek, Cambridge, UK).

Skin and microclimate temperature

Skin temperature was measured on the chest using a skin thermistor (Grants Instruments,Cambridge, UK) attached with adhesive tape. The temperature of the microclimate betweenthe top of the scalp and fire hood (referred to as hood temperature) was measured using athermistor threaded into the fire hood. Chest, hood and rectal temperature were recorded on adata logger (modified Squirrel 1000 series, Eltek, Cambridge, UK) at 1 min intervals. The datalogger was wrapped in a roasting bag and placed in a holder worn under the tunic around thewaist, or neck depending on the instructors' preference.

Heart rate

Heart rate was measured using a Polar heart rate monitor (Polar Electro Oy, Kempele,Finland) and recorded every 15 s throughout the exercise.

Sweat rate and fluid intake

Fluid intake during the exercise was measured by weighing (Bench scales, Ohaus UK Ltd,Leicester, UK; accuracy 5 g) the water bottles provided to each instructor before the exercise(after providing a urine sample) and at the end of the exercise. Total sweat rate was calculatedfrom the change in "naked" body weight before and after the exercise taking into account fluidintake.

Urine analysis

The instructors provided urine samples before the Hot Fire exercise for measurement of pHand specific gravity using a Multistix (Bayer Diagnostics, Munchen, Germany).

3.4 Flat drag rescue

Preliminary data analysis and discussions with the instructors indicated that the duration of theinterval between the Hot Fire exercise and Rhot was critical in their perceived ability to performthe rescue task. One subject reported that he would not have attempted the Rhot immediatelyon finishing his Hot Fire exercise. However, the transit time to get him from the Hot Fireexercise to where the rescue was conducted (9 min) was sufficient for him to recover enoughto perform the Rhot. In light of this, another trial was conducted with a minimal time delaybetween the end of the Hot Fire exercise and the rescue task (Rflat).

Six instructors undertook Rflat (three of which also undertook Rcontrol and Rhot) and onesubject (instructor no. 9) undertook two Rflat separated by 3 months giving a total of seventrials. The rescue task was performed immediately after completing a Hot Fire exercise duringwhich they were monitored as above with the exception that temperature recordings weremade every 15 s rather than every minute. The Hot Fire exercises were conducted in the


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purpose built fire houses within the FSC - the Ship (n=2), the BA School (n=3) and Industrial B(n=2) buildings.

The rescue task (Rflat) involved dragging a 68.5 kg dummy wearing SCBA (16.5 kg) aroundcones placed 10 m apart for a total distance of 30 m (Figure 3.2). In order to ensure theminimum time delay between the end of the Hot Fire exercise and rescue task, the cones anddummy were placed close to the exit of the fire building. Before commencing the rescue taskthe instructors were asked to rate their ability to perform the rescue (0 to 7). If they gave arating of 5 or above their rectal temperature was checked and if this was above 39.5C or theygave a rating of 7 they did not conduct the rescue task. Time taken to complete the task wasrecorded and heart rate was measured every 5 s (Polar Electro Oy, Kempele, Finland). At theend of the Rflat the instructors were asked their rating of perceived exertion (6-20 scale Borg)and 2 min later a finger prick sample blood was taken for measurement of blood lactateconcentration (Lactate Pro, Arkray Inc, Kyoto, Japan).

Figure 3.2 Instructor undertaking Rflat.

3.5 Clothing

The clothing worn by the instructors varied according to the brigade they came from and theirown personal preferences. In general, the instructors wore a T-shirt and overalls under theirtwo-piece protective clothing (from various manufacturers including: Bristol, PBI Gold and

Delta). They also wore a fire hood, either a Cromwell or Galley helmet and protective gloves.On their feet they wore 2 pairs of socks and standard steel toe-cap fire boots. The mass of thetotal clothing ensemble was 10.6 0.7 kg, the SCBA weighed 12.4 kg and the physiologicalmonitoring equipment weighed 0.9 kg.

3.6 Assessment of physical fitness and percentage body fat

Aerobic capacity was estimated by measurement of heart rate during a submaximal step testor cycle ergometer test. For the step test, the instructors stepped at a constant pace for 6 min


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wearing shorts or track suit, T-shirt and training shoes. Oxygen consumption for the steppingexercise was calculated, and with the heart rate measured during the last 2 minutes ofexercise, was used to predict maximal oxygen consumption ( V O2max) using the AstrandRyhming nomogram (1954). The value thus obtained was corrected for age. For the cycleergometer test, V O2max was predicted from work load and heart rate using the FitechCounsellor Series (Fitech Ltd, Chester).

Percentage body fat was calculated from measurements of skinfold thickness taken at thebiceps, triceps, subscapular and supra-iliac according to Durnin and Womersley (1974).

3.7 Statistical analysis

Data are given as the arithmetic mean standard deviation. A test of normality (Kolmongorov-Smirnov) and Levene's test of equal variance were conducted on the data, following whichheart rate, oxygen consumption, RPE and blood lactate concentrations in Rcontrol and Rhotwere analysed using a paired t-test. Relationships between the perceived ability to perform arescue and various measures made prior to Rhot and Rflat were analysed using a Spearmans

rank correlation coefficient. Statistical significance was taken at the 5% level (P


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4. Results

4.1 General

The physical characteristics of the instructors monitored are shown in Table 4.1.

Table 4.1. Physical characteristics and fire fighting experience of instructors. BAI = breathing

apparatus instructor, FSC = Fire Service College. Instructor 13 was monitored on his first dayas a BAI at the FSC. R 1 = Simulated Rescue Task 1 (Rhot and Rcontrol), R 2 = SimulatedRescue Task 2 (Rflat). Predicted V O2max values that are marked with an asterix wereobtained from a submaximal cycle ergometer test (Fitech).

4.2 Hot fire exercises

4.2.1 Introduction

The average duration of the Hot Fire exercises prior to Rhot (HF1) were 40.0 24.3 min (range12 to 92 min) and prior to Rflat (HF2) were 41.3 12.8 min (range 22.8 to 62.5 min). HF1 and

HF2 were rated as 60 18 and 59 24 for demand and 59 19 and 52 26 for heatrespectively (0 corresponded to an exercise which was not hot/demanding; 50 to one ofaverage heat/demand and 100 to one that was very hot/demanding). The individual data forHF1 and HF2 are given in Appendices C and D.

4.2.2 Environmental temperature

The mean and maximum environmental temperatures recorded within the fire building duringthe Hot Fire exercises are shown in Table 4.2. Data were not collected for all of the instructorsas they changed floors and were therefore not in the same area as the "thermocouple tree".


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The mean temperature measured on the outside of the instructors' tunic was 48.4 11.2C(n=9) during HF1 and 39.2 15.6C (n=5) during HF2. The maximum temperature measuredwas 95.6 49.2C during HF1 and 79.2 31.9C during HF2.

Environmental Temperature (C)HF1 HF2

Height of thermocouple mean maximum mean maximum0.3 m 33 9 52 22 22 13 36 40.6 m 45 12 75 24 27 19 57 490.9 m 54 15 90 30 33 26 79 771.2 m 63 18 107 36 56 57 132 1081.5 m 75 25 135 51 87 87 188 1161.8 m 99 38 174 61 112 83 233 131

Table 4.2. Mean and maximum temperature standard deviation recorded from the"thermocouple trees" during the Hot Fire exercises, n = 5 for HF1 and n = 3 for HF2.

4.2.3 Deep body temperature

Rectal temperatures (Tre) during the Hot Fire exercises are shown in Table 4.3 and Figures5.1 and 5.2. The individual responses varied considerably depending on the duration of theexercise and the fire loading (Figures 5.1 and 5.2). The highest Tre recorded during HF1 was38.8C in 2 instructors and during HF2 it was 39.05C in one instructor. After the Hot Fireexercise, Tre increased slightly prior to the start of simulated rescue task and showed a furtherelevation after completion of the rescue task despite the tunic being opened fully and thegloves and helmet removed.

HF1 HF2Start Hot Fire 37.60 0.13C 37.62 0.29C (n=7)End Hot Fire 37.99 0.37C 38.12 0.68C (n=5)Start rescue 38.05 0.39C 38.29 0.73C (n=6)End rescue 38.20 0.35C 38.43 0.68C (n=6)Total change 0.60 0.35C 0.83 0.56C (n=6)

Table 4.3 Mean rectal temperature standard deviation before and after Hot Fire exercisesand simulated rescue tasks. Values represent the mean and standard deviations of 10observations for HF1 and as indicated in parenthesises for HF2.


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Figure 4.1 Rectal temperature during HF1 and Rhot. Each line represents the rectaltemperature of an individual instructor. The open circle indicates the end of HF1 and the closedsquare the start of Rhot.

Figure 4.2 Rectal temperature during HF2 and Rflat. Each line represents the rectaltemperature of an individual instructor. The open circle indicates the end of HF2 and the closedsquare the start of Rflat.

4.2.4 Skin and microclimate temperature

Chest Tsk averaged 38.01 0.91C during HF1 and the maximum averaged 39.14 1.38C(range 37.0 to 41.2C; n=9). During HF2, the mean chest Tsk was 37.79 1.25C and themaximum averaged 38.85 1.62C (range 36.7 to 41.2C; n=7).

Hood T averaged 37.02 1.38C (n=8) during HF1 and the maximum averaged 40.08 2.51C (range 37.15 to 44.65C, n=8). One subject had a head T of over 44C for 5 min.During HF2, the mean hood T was 36.95 2.66C and the maximum averaged 39.21


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2.88C (range 36.65 to 43.05C; n=6).

4.2.5 Heart rate

Heart rate (HR) during the Hot Fire exercises is shown in Figure 4.3. The maximum HRrecorded equated to 87 5% of the instructors' maximum HR (HRmax - either recorded orpredicted from age) in HF1 and 77 11% in HF2. In most cases (13/15), HR was found to

increase gradually during the Hot Fire exercises, the difference between the average HRduring the first and last minute of HF1 was 29.4 22.4 bpm (n=9) and 26.5 28.0 bpm (n=6)for HF2 (see Appendices C and D for individual data).

Figure 4.3 Mean and maximum heart rate during the Hot Fire exercises. Bars represent themean and the error bars the standard deviation of 9 observations for HF1 and 6 observationsfor HF2.

4.2.6 Hydration statusPrior to the Hot Fire exercises the mean urine specific gravity was 1.019 0.009 (n=7) for HF1and 1.023 0.009 (n=6) for HF2. The total sweat loss, fluid intake and fluid deficit recorded forthe Hot Fire exercises and rescue tasks are given in Figure 4.4. Assuming the sweat lossoccurred predominantly from the start of the Hot Fire exercise to the end of the rescue task,this gave a sweat rate of 35 25 ml.min -1 in HF1 (n=10) and 23 12 ml.min -1 in HF2 (n=7).The fluid deficit equated to a loss of 0.6 0.6% body mass in HF1 and 0.6 0.4% body massin HF2.


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Figure 4.4. Mean sweat loss, fluid intake and fluid deficit during the Hot Fire exercises and therescue tasks. Mean and standard deviation given for both conditions (n= 10 for HF1 and n=7for HF2).

4.2.7 DiscomfortThe average discomfort votes during HF1 and HF2 were 3.1 1.3 and 3.1 0.8 respectively.The corresponding maximum discomfort averaged 4.2 1.8 and 3.7 1.1 (1 = comfortable; 7= maximum discomfort). In one HF1 the maximum discomfort (7) was reported after 5 to 7 minof the start of the exercise. This was due to the very high heat load from the fire in theDomestic building that was compounded by the instructor being unable to leave his post as hisradio had malfunctioned. Table 4.4 shows the physiological measurements taken at this time.

Measurements at 5 to 7 minDiscomfort 7

HR 149 bpmTre 37.70CChest Tsk 40.40CHood T 44.65C

Table 4.4. Physiological status of an instructor corresponding to the time when he reported amaximum discomfort vote during a Hot Fire exercise (HF1) in the Domestic building.

4.3 Rcontrol and Rhot

Prior to the Rhot the instructors' RPE and rating of inability to perform the rescue weresignificantly higher than prior to Rcontrol (P


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Table 4.5. Average rating of perceived exertion and ability to perform the rescue, heart rateand blood lactate levels prior to undertaking Rcontrol and Rhot. Values are the mean standard deviation, n=10 unless otherwise stated. * indicates significant (P


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significant difference between Rcontrol and Rhot (P0.001) than Rcontrol (Rhot = 15.7 2.1; Rcontrol = 13.3 2.4).

No correlation was found between the perceived ability to perform Rhot and the followingvariables: rectal temperature, heart rate (expressed as percentage of maximum heart rate),chest or hood temperature recorded over 1 minute prior to commencing Rhot, ratings of heatand demand for HF1 duration of rest between HF1 and Rhot or time to complete Rhot.

4.4 Rflat

Rflat was performed 79.0 65.0 s after completing a Hot Fire exercise (HF2) in an ambienttemperature of 16.3 6.7C (n=7). The subjects rating of their ability to perform the rescueaveraged 4.1 1.5 (0 = easy; 7 = impossible; n=7). On six occasions the full 30 m drag wassuccessfully completed, on one occasion the instructor dragged the dummy for 20 m before

stopping through exhaustion. The individual data for Rflat are given in Table 4.7.The mean time to complete the 30 m rescue task was 41.7 6.9 s (n=6). For the instructorswhere the split times were recorded and the full 30 m rescue task was completed (n=5), themean time taken to drag the dummy 10 m was 11.0 3.7 s and 25.7 3.6 s for 20 m. This wasconsiderably faster than for the instructor who stopped at 20 m (Table 4.7).

Mean HR prior to Rflat and after HF2 was 129 32 bpm. The mean HR during Rflat was 172.7 19.1 bpm and maximum HR averaged 182.3 19.7 bpm which corresponded to 96 5% ofthe instructors HRmax (n=6). At the end of Rflat, RPE averaged 16.3 2.4 and the mean bloodlactate level was 8.3 1.9 mmol.L -1 (n=7).

Perceived ability to perform Rflat was positively correlated with Tre and Tchest prior to therescue task (Tre: R 2 = 0.771, n = 6, P


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blood lactate levels 2 min post Rflat are given for each instructor. The subject highlighted wasunable to complete the 30 m rescue task. The mean and standard deviation are for all the dataobtained.

Figure 4.6. Correlation between perceived ability to perform Rflat and rating of heat anddemand of HF2. Ability to perform the rescue was rated on a scale of 0 to 7 (0 being easily, 7being impossible). Heat and demand of the Hot Fire exercise were rated separately on a scaleof 0 to 100, 0 corresponded to an exercise which was not hot/demanding, 50 to one of averageheat/demand and 100 to one which was very hot/demanding. The rating of heat and demand isthe sum of the two ratings (n=7).


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5. Discussion

5.1 General

As soon as 10 min after a Hot Fire training exercise, all ten instructors were able to complete asimulated rescue task involving dragging a 81 kg dummy 15 m along a corridor containingobstacles and then down 2 flights of stairs (Rcontrol and Rhot). From the questionnaireresponses it is likely that this rescue task is representative of most worst case scenarios withinthe UK Brigades. As expected, the instructors found the rescue task harder after they hadacted as a safety officer in a Hot Fire exercise. This was reflected in their significantly higherheart rates and RPE scores following Rhot (Figure 4.5). It is therefore encouraging that,despite being exposed to the heat for an average of 40 min, all the instructors monitored werecapable of successfully performing a rescue task simulating the worst case scenario of acollapsed fire-fighter in a live fire training exercise.

5.2 Hot fire exercises and deep body temperatureWhilst the rescue task probably did represent the worst case scenario judging from theresponses to the questionnaire sent out to the Brigades (section 2 and Table 2.3), other factorsmay not have been. The mean Tre at the end of the Hot Fire exercise (HF1) was 38C with themaximum recorded being 38.8C. This is lower than that recorded previously with fire-fighterinstructors, where the mean deep body temperature at the end of the fire-fighter trainingexercises was 38.5C with 8 out of 26 Hot Fire exercises resulting in a deep body temperatureexceeding 39C (Eglin and Tipton 2000). Other studies monitoring fire-fighters have recordeddeep body temperatures of 38.3C after two 15 min periods of heavy dynamic work (Ilmarinenet al. 1997), 39C after 24 min of a search and rescue task (Romet and Frim 1987) and 39.8Cafter a 16 min ceiling haul (Smith et al. 1997). It should, however be noted that in these studiesthe fire-fighters were undertaking strenuous work, and whilst their heat exposure was shorter,their metabolic heat production would have been much higher.

The lower deep body temperatures recorded during HF1 could have been a result of controlmeasures put in place following the results obtained from monitoring instructors from the FSCduring Hot Fire exercises (Eglin and Tipton, 2000). The recommendations from that study werethat fire-fighters should be encouraged to actively cool down and minimise their physicalactivity after a live fire training exercise until their deep body temperature has returned tonormal. It was also recommended that instructors should not be re-exposed to the heat withina couple of hours and should be encouraged to drink more fluids and monitor their hydrationstatus. Since this study was conducted there has been a complete job rotation at the FSC andall the personnel have changed. As a consequence some of the practices put in place as aresult of the recommendations may have been lost. In the present study it was very rare for aninstructor to come outside the building for a rest during the Hot Fire exercise, where previouslythey came out on average for 10.6 11.0 min (n = 19 out of 27 Hot Fire exercises) over the 40min exercise period. This change in practice could be due to the instructors being unable toleave their post due to the continual presence of students on their section of the building, or areduction in fire loading within the fire houses resulting in the instructors not finding itnecessary to cool down during the Hot Fire exercise. Lower environmental temperatures weremeasured in the present study (Table 4.1) thus supporting the latter explanation and helping


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explain the lower Tre recorded.

5.3 Simulated rescue tasks

After completing their Hot Fire exercise the instructors had on average a rest period of 10 minbefore attempting the rescue task. This delay in commencing the rescue was an inevitable

consequence of the need to transport the instructor to the fire building where the rescue taskwas conducted, and the need to exchange the SCBA worn by the instructors for the Metamaxsystem used to measure oxygen consumption. Many of the instructors commented that theywould have found the rescue task more difficult if they had to conduct it immediately the HotFire exercise had ended. One instructor reported he would not have attempted the rescue taskimmediately after a very hot Hot Fire exercise (Table 4.4), but was able to do so with the 9 minrest period. In light of this, another trial was conducted with a minimal time delay between theend of the Hot Fire exercise and the rescue task.

Rflat involved dragging an 85 kg dummy 30 m along a flat surface which is the furthestdistance reported by the brigades that a casualty may have to be moved to safety during a live

fire training exercise. On 6 out of 7 occasions the instructors were able to successfully performRflat 1 min 19 s after acting as a safety officer in a Hot Fire exercise which resulted in their Trebeing elevated, on average, to 38.1C. The one instructor who did not manage to complete thefull 30 m rescue task was able to drag the dummy 20 m. This is further than the furthestdistance a safety officer would have to move a casualty on their own, based on the responsesto the questionnaire (mean 5.9 m, range 1.5 to 15 m). Therefore, even without a rest period,the results suggest that, within the limits of the current study, the instructors are capable ofsuccessfully performing a rescue at the end of a Hot Fire exercise. It should be noted,however, that in a scenario where the Hot Fire exercise was more arduous resulting in higherdeep body temperatures and greater levels of dehydration, or the instructor was less fit orexperienced or the casualty was heavier than 85 kg a rescue may not be possible. This also

presumes that it is acceptable to have the instructors under such a high level of strain whilstperforming a rescue.

5.4 Physical demand of the rescue tasks

Data from Rcontrol and Rhot demonstrate that performing a rescue is a demanding task (Table4.6) with HR being close to the instructors' HRmax (Figure 4.5). Despite being exactly thesame task, Rhot was found to require a smaller metabolic demand than Rcontrol (Table 4.6).This was probably a learning effect as for safety reasons the Rcontrol was conducted first andskill was required to turn the dummy around 180 in a confined space at the start of the rescue.As a result the aerobic demand of the task was similar in both rescues with an increased

additional anaerobic demand in Rcontrol (Table 4.6) however, blood lactate levels measured 2min post Rcontrol and Rhot were similar. The blood lactate levels 2 min after the rescue tasksaveraged 6 mmol.L -1 indicating the task was strenuous.

Heart rate prior to and during Rhot was higher than for Rcontrol (Table 4.5, Figure 4.5). DuringRhot, the instructors' HR was at, or very close to, their HRmax (Figure 4.5); whilst HR waslower in Rcontrol it still reached 87% HRmax. Interestingly, although significantly higher afterRhot, the RPE scores following the rescue tasks did not reflect these very high HR. The meanRPE for Rhot was 15.7 2.1 and that for Rcontrol was 13.3 2.4 which correspond to a rating


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of "heavy to very heavy" and "somewhat heavy" respectively. With such high HR one wouldnormally expect RPE scores above 18 (Borg 1982). However, the rescue task involves a lot ofupper body musculature and this has been found to elevate HR more than the equivalent lowerbody exercise (Toner et al. 1990).

5.5 Heat and performance

Heart rate before and during Rhot was higher than with Rcontrol due to an increase in bodytemperature (Figure 4.5, Table 4.5). In the heat, peripheral blood vessels dilate to enhanceheat dissipation and therefore peripheral blood flow increases. Therefore, during exercise inthe heat a greater cardiac output is required to support the increased blood flow to the activemusculature and periphery. Cardiac output during exercise in the heat may be furthercompromised by a reduction in plasma volume (caused by dehydration) and venous returnwhich will reduce stroke volume. Therefore fire-fighting tasks at an elevated body temperaturewill require a greater cardiac output, but due to heat related decrease in plasma volumemaximum cardiac output will be decreased. Stroke volume has been found to decrease by35% following three 7 min bouts of strenuous fire-fighting tasks in the heat. This resulted in a

30% reduction in cardiac output as HR could only be increased by 8% before reaching the fire-fighters' HRmax (Smith et al. 2001a). Using the same protocol, but different subjects, Smith etal. (2001b) demonstrated a 15% reduction in plasma volume occurred after the 21 min of fire-fighting tasks. The results from the current study suggest stroke volume may have beendecreased in Rhot compared to Rcontrol as HR was significantly higher despite the totalmetabolic demand of Rhot being lower than Rcontrol.

Prolonged exposure to heat, such as during a Hot Fire exercise, reduces physical capacity andperformance (Nielsen et al. 1981; Hargreaves and Febbraio 1998). This is due to an elevationin deep body temperature or dehydration or a combination of both factors (Nielsen et al. 1981).Convergence of mean Tsk and deep body temperature has been suggested as a good

predictor of the limit of heat tolerance for workers in encapsulated garments (Pandolf andGoldman 1978). However, Nunneley et al. (1992) have suggested that whilst convergenceoccurs under severe heat stress, motivated individuals can continue working beyond this point.Tsk on the chest during HF1 increased above Tre in 8 out of 9 instructors and during HF2 in 5out of 7 instructors. In those instructors where convergence of Tre and Tsk was not observedtheir Tre had only increased by an average of 0.1C by the end of the Hot Fire exercise. In theinstructors where convergence was observed maximal discomfort votes during the Hot Fireexercise averaged 4.0 (range 1 to 5.5 - excluding the instructor who reported 7 after 5 min of aHF1, Table 4.4) suggesting they were not close to their limit of heat tolerance. Given the muchhigher ambient temperatures experienced in the present study, compared to the laboratorybased studies (Pandolf and Goldman 1978; Nunneley et al. 1992), it is unlikely thatconvergence of chest Tsk and Tre could be used to predict tolerance time during fire-fightingtraining exercises.

The instructor who reported a discomfort vote of 7 had a high hood T as a result of the highradiant heat load in the building. The T under the fire hood for this instructor was 44C for 5min, which is the lowest skin temperature to cause skin burning after contact with an object for6 hours (Moritz and Henriques 1947). Therefore, although very uncomfortable, this high T didnot result in a burn. The maximum Tsk recorded in the other Hot Fire exercises whilst high,were below 44C and therefore would have an adverse effect on comfort but not induce a burn.


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5.6 Hydration status and performance

Sweat loss during the Hot Fire exercises and rescue tasks resulted in very mild hypohydration,less than 1% body weight, assuming the water consumed during the Hot Fire exercise wasfully absorbed into the blood stream (Figure 4.4). From the literature pertaining to sportsperformance such a low levels of dehydration is unlikely to affect either thermoregulation or

performance (Cheuvront and Haymes 2001; Yoshida et al. 2002). However studies on fire-fighters working in the heat have shown a 15% reduction in plasma volume after only three 7min bouts of fire-fighting tasks (Smith et al. 2001b). In addition, dehydration will augment theeffect of hyperthermia on the cardiovascular system resulting in a greater reduction in strokevolume and therefore cardiac output (Gonzalez-Alonso et al. 1997). This is particularly relevantto a student fire-fighter who has undertaken strenuous fire-fighting tasks in the heat and is thenrequired to aid in the rescue of a fellow fire-fighter. The level of dehydration as a result ofsweat loss during a Hot Fire exercise will be compounded if the fire-fighter starts the exercisein a hypohydrated state. The hydration status of the instructors prior to the Hot Fire exerciseswas assessed by measuring urine specific gravity (Usg). The average Usg prior to HF1 was1.019 and 1.023 prior to HF2 suggesting that the instructors were euhydrated (Armstrong et al.

1994).

5.7 Fitness and performance

The instructors monitored during the current study had similar levels of fitness to those used inother studies of fire-fighters judging from their predicted V O2max levels (Lemon and Hermiston1977; White and Hodous 1987 and 1988; Ben-Ezra and Verstrete 1988; Faff and Tutak 1989;Louhevaara et al. 1995; Home Office 1996; Smith and Petruzzello 1998; Eglin and Tipton2000). The fitter an individual is, the more easily they will be able to perform a given task. Theaverage oxygen consumption during Rcontrol and Rhot was 2.37 0.33 L.min -1. This value issimilar to a previous study measuring oxygen consumption during a victim rescue (Lemon and

Hermiston 1977). Thus for the instructors with a high V O2max this represented a lowerpercentage of their V O2max than for the less fit instructors. However, the task was self-pacedand therefore the instructor could adjust their pace according to the level of physiologicalstrain.

There are inherent errors in using a submaximal test for determining V O2max as severalassumptions are made: there is a linear relationship between HR and V O2, all individuals havethe same stepping/cycling efficiency, and HRmax is 220-age (unless a higher HR wasrecorded during the rescue tasks). There was evidence to suggest that the predicted V O2maxvalues obtained using the Fitech cycle ergometer test gave a greater over-estimation of theindividuals aerobic capacity than the step test. Given that this test is used routinely at the FSC

and other brigades to give advice to fire-fighters on their fitness levels and training required,this submaximal test should be validated against a direct measure of V O2max in the fire-fighting population. Even when V O2max is determined directly during exhaustive exercise, ithas been suggested that a V O2max obtained during arm cranking may be more applicable todetermining the relative intensity of fire-fighting tasks requiring a large proportion of upper bodyactivity than a V O2max determined on a treadmill (Weafer 1999).

It was noticeable that the only instructor who could not complete the full 30 m dummy drag inRflat was the oldest fire-fighter and was one of the less fit instructors. Whilst, within limits, age


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per se has little effect on performance it is often associated with a decline in physical fitness(Hossack and Bruce 1982) as a result of a more sedentary life style (Buskirk and Hodgson1987). It is the reduction in fitness and therefore cardiovascular, respiratory andthermoregulatory function that will impair the ability of a fire-fighter to perform in the heat. Thisis supported by a study conducted by Faff and Tutak (1989) where fire-fighter exercisetolerance time in the heat was not found to be related to age (21 to 32 y vs. 36 to 42 y) but wasincreased with fitness (>39 ml.kg -1.min -1). It is also noteworthy that this instructor had the leastcurrent experience of hot wears as he was in a management position. Experience in Hot Fireexercises is important as not only will it result in favourable physiological adaptations throughheat acclimation (Armstrong and Maresh 1991), but will also enable the fire-fighter to keepcooler through behavioural adaptations such as knowing where the cooler areas of the buildingare.

5.8 Perceived ability to perform the rescue task

All the instructors perceived correctly that they would be able to perform Rcontrol and Rhot andas expected, they thought they were more able to perform Rcontrol than Rhot (Table 4.5). The

rating of their perceived ability to perform the Rhot was not correlated to any physiologicalvariable measured prior to the rescue task neither was it correlated to HR during Rhot. Theinstructor who did not complete Rflat gave a rating of 6 indicating that he thought he couldperform the rescue but would find it extremely difficult. Unlike Rhot, several of the variablesmeasured prior to Rflat correlated with their perceived ability to perform the rescue task. Thissuggests that Tre, chest Tsk and in particular the level of stress perceived during HF2influenced their perception of their ability to perform the rescue task (Figure 4.6). This suggeststhat elevated Tre and Tsk as a result of the stress of the Hot Fire exercise reduced theirperceived ability to perform the rescue task. It is unclear why no such correlations wereobserved with Rhot, this may have been due to the psychological benefit derived from the restperiod between HF1 and Rhot, however it should be borne in mind that the subject numbers

were small.

5.9 Cardiovascular risk in firefighters

A review of epidemiological studies by Guidotti (1995) on fire-fighter mortality concluded thatthere was no conclusive evidence to suggest that fire-fighters have an increased risk of deathfrom heart attack over the normal population. However, there may be a risk of sudden heartattack and cardiac decompensation following sudden maximal exertion or carbon monoxideexposure (Guidotti 1995). A survey of fire-fighters in the USA in 1993 indicated that heartattacks accounted for over 50% of all on-duty fire-fighter deaths, a similar statistic was foundfor deaths on the fireground (NFPA cited by Bone et al. 1994). 95% of these heart attacks were

attributed to stress and over exertion (NFPA cited by Bone et al. 1994). An earlier report on thecauses of line-of duty fire-fighter deaths in the USA between 1977 and 1986 found 47% ofdeaths (612) were caused by heart attacks (Picher 1987). 50% of these heart attacks wereassociated with fire suppression tasks, 25% with responding or returning from an alarm calland 6% occurred during training. Therefore exposure to heat during a Hot Fire exercise andsudden high intensity exercise such as rescuing a collapsed student fire-fighter could put theinstructor at increased risk of a fatal heart attack.

The risk of a cardiovascular accident is greater in an individual who has underlying


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cardiovascular disease. This is supported by the findings of the survey conducted by Picher(1987), where of the fire-fighters whose medical condition prior to their fatal heart attack wasknown (n=257), 40.5 % had some prior heart-related condition (e.g. previous heart attacks orcoronary bypass surgery) that had impaired their performance. In addition, 39.3% had severearteriosclerotic heart disease (defined as arterial occulsion greater than 50%) and 9% hadhypertension.

Good physical fitness will reduce the strain associated with carrying out a task and thereforereduce the risk of a heart attack. In a study assessing the physical fitness of 150 full time fire-fighters from a municipal fire department it was found that the fire-fighters had a similar level offitness to that of the general sedentary population (Saupe et al. 1991). In addition, in Saupeand co-workers study the vast majority of fire-fighters over 30 years old fell below therecommended minimum VO 2max of 39 ml.kg -1.min -1. It is not clear whether, since this paperwas published, measures to increase the physical fitness of fire-fighters have succeeded, orwhether a similar pattern of fitness is found in fire-fighters in UK brigades. Given the very highheart rates observed during the rescue tasks, particularly after completing the Hot Fireexercise, it would be prudent to medically screen safety officers to assess their fitness levelsand their risk of heart attack. The responses from the questionnaire show that prior tobecoming a safety officer a fire-fighter is given a medical in approximately half the brigades inthe UK, whereas in only 7 brigades a fitness test is conducted (Table 2.5). Still fewer brigadesconduct periodic fitness testing of their instructors (Table 2.5). Knowledge of the fitness levelsof the instructors could help in managing a Hot Fire training exercise by positioning the fittestsafety officer in the least accessible regions of a fire building were the rescue of a collapsedstudent would be more difficult. Alternatively management systems could be put in place whichmean that, where possible, instructors would not have to perform a rescue when eitherhyperthermic or hypohydrated. This may involve rotating staff during the Hot Fire exercise toreduce their increase in deep body temperature or ensuring there was a rescue team onstandby outside the building.


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6. Conclusions

The physiological responses of the instructors observed during the Hot Fire trainingexercises were within the range of those reported previously.

The rescue tasks devised were representative of the worst case scenario that a singleinstructor may face according to the responses to a questionnaire sent out to all thebrigades in the UK.

These rescue tasks were very demanding and approached the physiological limits of themajority of current instructors.

Despite the arduous nature of the rescue tasks, the instructors monitored were capable ofperforming a rescue task after acting as a safety officer in a live fire training exercise.

Evidence from this study showing a sweat loss of 1.5 L during the Hot Fire exercise andrescue task confirms the importance for all fire-fighters involved in Hot Fire trainingexercises to be fully hydrated at all times.

It is likely that in less favourable situations (higher deep body temperatures, greater levelsof dehydration, less fit or experienced instructor, or a casualty heavier than 85 kg) arescue may not be possible, or attempts to continue to do so may result in a "heart attack"in the rescuer.

It should also be considered whether it is acceptable to expect less fit fire-fighterinstructors to undertake such a strenuous task in combination with heat exposure.


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7. Recommendations

It is recommended that physical fitness tests for instructors acting as safety officers duringlive fire training exercises are undertaken prior to starting the post and then followed upevery 6 months to 1 year. From the literature on the physical demand of fire-fighting tasks(Bilzon et al. 2001; Gledhill and Jamnik 1992) and the VO2 measured during the rescuetask in the current study it is suggested that the minimum VO2 max should be 40 to 45ml.kg-1.min-1. However, lower levels of fitness may be overcome by using managementstrategies as suggested below.

Given that fitness assessment is important prior, and during, employment as a safetyofficer, any test used to assess aerobic capacity should be properly validated against adirect measure of VO2max in an appropriate population (i.e. fire-fighters representative ofthe instructor population - aged 25 to 45 y).

The information obtained from the fitness tests could be used as a management tool to

determine where instructors should be placed within a fire building. The fittest instructor,who is likely to be most capable of performing a rescue should be placed in the leastaccessible region of the fire building. If the training exercise is likely to be arduous and/orthe instructors are less fit, it is recommended that extra staff are available outside thebuilding in case a rescue is required. Alternatively, staff could be rotated so that theirexposure to the heat is reduced.

The instructors monitored were fairly accurate in their perceived ability to perform therescue task and this was related to the stress experienced during the Hot Fire exercise.Therefore, by asking the instructors how they perceive their level of stress during a live firetraining exercise (using a simple 1 to 7 scale) an indication of their ability to perform arescue will be obtained. This could then be used to relocate instructors during the Hot Fireexercise to avoid a reduction in performance caused by heat stress.

Prior to the start of Hot Fire training exercises the instructors and student fire-fightersshould be encouraged to have their tunics open to prevent their deep body temperaturefrom rising before they start the exercise. The instructors should rest outside the firebuilding whenever possible during the exercises to reduce their heat exposure. In additionall fire-fighters should be encouraged to actively cool down after the fire-fighter trainingexercises to prevent their deep body temperature from rising further. This can be achievedsimply by opening tunics (with the possible use of fans, Carter et al. 1999) or by immersingthe hands in cold water (House 1998).

Fire-fighter instructors and students should be encouraged to drink plenty of fluids before,during (where possible) and after a heat exposure. They should drink at least 1.5 timesthe amount of weight they have lost through sweating (e.g. if they have lost 1 kg during anexercise they should drink 1.5 L fluid). It will take approximately 4 hours to rehydrate(Bilzon et al. 2000), though this will vary depending on the extent of dehydration and thevolume and nature of fluid ingested. Monitoring of hydration status should be encouraged,this can be done by weighing every day or checking urine colour against a chart relatingurine colour to hydration status. It should be remembered that alcohol consumption andillness can result in dehydration.


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Acknowledgements

We would especially like to like to thank the following people: all the instructors at the FireService College, Moreton in Marsh for participating in the trial and giving valuable feedbackthroughout; Paul Grimshaw for supporting the study and allowing us to use the facilities at the

FSC, Sue Coles and Guy Roberts for all their help and support during the trial; JonathanDalzell for his excellent help with the data collection; Frank Golden for help and advice inwriting the report, all the brigade training officers who responded to the questionnaire.


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References

Armstrong, L.E. and Maresh, C.M. 1991, The induction and decay of heat acclimatisation intrained atheletes, Sports Med, 12, 302-12.

Armstrong, L.E., Maresh, C.M., Castellani, J.W., Bergeron, M.F., Kenefick, R.W., LaGasse,K.E. and Riebe, D. 1994, Urinary indices of hydration status. Ergonom, 41, 1845-58.

Astrand, P.O. and Ryhming, I. 1954, A Nomogram for calculation of aerobic capacity (physicalfitness) from pulse rate during submaximal work. J Appl Physiol, 7, 218-21.

Barnard R.J. and Duncan H.W. 1975, Heart rate and ECG responses of fire fighters. J Occup Med 17 ,247-250.

Ben-Ezra, V. and Verstraete, R. 1988, Stair climbing: an alternative exercise modality forfirefighters. J Occup Med, 30, 103-5.

Bilzon, J.L.J, Allsopp, A.J. and Williams C. (2000) Short-term recovery from prolongedconstant pace running in a warm environment: the effectiveness of a carbohydrate-electrolytesolution. Eur J Appl Physiol , 82 ,305-312.

Bilzon, J.L.J., Scarpello, E.G., Smith, C.V., Ravenhill, N.A. and Rayson, M.P. 2001,Characterization of the metabolic demands of simulated shipboard Royal Navy fire-fightingtasks. Ergonom, 44, 766-80.

Bone, B.G., Clark, D.F., Smith, D.L. and Petruzzello, S.J. 1994, Physiological responses toworking in bunker gear: a comparative study. Fire Engineering, November, 52-5.

Borg G. 1970, Perceived exertion as an indictor of somatic stress. Scand J Rehab Med, 2, 92-8.

Borg, G. 1982, Psychophysical bases of perceived exertion. Med Sci Sports Exercise, 14 , 377-381.

Buskirk, E.R. and Hodgson, J.L. 1987, Age and aerobic power: the rate of change in men andwomen. Fed Proc , 46 , 1824-1829.

Carter, J.B., Banister, E.W. and Morrison, J.B. (1999) Effectiveness of rest pauses and cooling

in alleviation of heat stress during simulated fire-fighting activity. Ergonom, 42 ,299-313Cheuvront, S.N. and Haymes, E.M. 2001, Thermoregulation and marathon running. Sports Medicine, 31, 743-62.

Duggan A. 1988, Energy costs of stepping in protective clothing ensembles. Ergonom 31 ,3-11.

Duncan H.W., Gardner G.W. and Barnard R.J. 1979, Physiological responses of men workingin fire fighting equipment in the heat. Ergonom 22 ,521-527.


39/42

Durnin, J.V.G.A. and Womersley, J. 1974, Body fat assessed from total body density and itsestimation from skinfold thickness: measurements on 481 men and women aged from 16 to 72years. Br J Nutr, 32, 77-96.

Eglin, C.M. and Tipton, M.J. Physiological monitoring of fire-fighter instructors during training.London. FRDG, Home Office. 2000; 1/2000.

Faff, J. and Tutak, T. 1989, Physiological responses to working with fire fighting equipment inthe heat in relation to subjective fatigue. Ergonom, 32, 629-38.

Foster, J.A. and Roberts, G.V. 1994, Measurements of the firefighting environment. FireResearch Development Group, Research Report Number 61.

Gledhill, N. and Jamnik V.K. 1992, Characterisation of the physical demands of firefighting.Can J Sport Sci 17 , 207-213.

Goldman R.F. 1990, Heat stress in firefighting. Fire Eng 47-53.

Gonzalez-Alonso, J., Mora-Rodriguez, R., Below, P.R. and Coyle, E.F. 1997, Dehydrationmarkedly impairs cardiovascular function in hyperthermic endurance atheletes during exercise.J Appl Physiol, 82, 1229-36.

Guidotti, T.L. 1995, Occupational mortality amoung firefighters:assessing the association. J Occup Med, 37, 1348-56.

Hargreaves, M. and Febbraio, M. 1998, Limits to exercise performance in the heat. Int J Sports Med, 19, S115-6.

Home Office 1996, Study of the physiological effects of wearing breathing apparatus. FireResearch and Development Group Report No. 13/96.

Hossack, K.F. and Bruce, R.A. 1982, Maximal cardiac function in sedentary normal men andwomen: comparison of age-related changes. J Appl Physiol , 53 , 799-804.

House, J.R. (1998) Extremity cooling as a method for reducing heat strain. J Defence Sci,3,108-114

Ilmarinen, R., Louhevaara, V., Griefahn, B., and Kunemund, C. 1997, Thermal and cardiacstrain in strenuous fire-fighting and rescue tasks in the extreme heat. in B. Nielsen Johannsenand R. Nielsen (eds.), Thermal Physiology, The August Krogh Institute. 39

Lemon, P.W.R. and Hermiston, R.T. 1977, The human energy cost of fire fighting. J Occup Med, 19, 558-62.

Louhevaara, V., Ilmarinen, R., Griefahn, B., Kunemund, C. and Makinen, H. 1995, Maximalphysical work performance with European standard based fire-protective clothing system andequipment in relation to individual characteristics, Eur J Physiol, 71, 223-9.

Lusa, S., Louhevaara, V., Smolander, J., Kivimaki, M. and Korhonen, O. 1993, Physiological


40/42

responses of firefighting students during simulated smoke-diving in the heat. Am Ind Hyg Assoc J 54 , 228-231.

Moritz A.R. and Henriques F.C. 1947, Studies of thermal injury II. The relative importance oftime and surface temperature in the causation of cutaneous burns. Am J Pathol Sept :695-720.

Nielsen, B., Kubica, R., Bonnesen, A., Rasmussen, I.B., Stoklosa, J. and Wilk, B. 1981,Physical work capacity after dehydration and hyperthermia. Scand J Sports Sci, 3, 2-10.

Nunneley, S.A., Antunano, M.J. and Bomalaski, S.H. 1992, Thermal convergence fails topredict heat tolerance limits. Aviat Space Environ Med, 63, 886-90.

Pandolf, K.B. and Goldman, R.F. 1978, Convergence of skin and rectal temperatures as acriterion for heat tolerance. Aviat Space Environ Med, 49, 1095-101.

Pascoe, D.D., Bellingar, T.A. and McCluskey, B.S. 1994, Clothing and exercise. II Influence ofclothing during exercise/work in environmental extremes. Sports Med 18 , 94-108.

Patton, J.F., Bidwell, T.E., Murphy, M.M., Mello, R.P. and Harp, M.E. 1995, Energy cost ofwearing chemical protective clothing during progressive treadmill walking. Aviat Space Environ Med 66 , 238-242

Picher, M.A. 1987, Fire fighter heart attacks. Fire Command , July , 16-20.

Ripple, G.R., Torrington, K.G. and Phillips, Y.Y. 1990, Predictive criteria for burns from briefthermal exposures. J Occup Med 32 , 215-219.

Romet, T.T. and Frim, J. 1987, Physiological responses to fire fighting activities. Eur J Appl Physiol, 56, 633-8.

Saupe, K., Sothmann, M. and Jasenof, D. 1991, Aging and the fitness of fire fighters: thecomplex issues involved in abolishing mandatory retirement ages. Am J Public Health, 81,1192-4.

Skoldstrom B. 1987, Physiological responses of firefighters to workload and thermal stress.Ergonom 30 ,1589-1597.

Smith, D.L., Petruzzello, S.J., Kramer, J.M., Warner, S.E., Bone, B.G. and Misner, J.E. 1995,Selected physiological and psychobiological responses to physical activity in differentconfigurations of firefighting gear. Ergonom, 38 , 2065-2077.

Smith, D.L., Petruzzello, S.J., Kramer, J.M. and Misner, J.E. 1997, The effects of differentthermal environments on the physiological and psychological responses of firefighters to atraining drill. Ergonom, 40, 500-10.

Smith, D.L. and Petruzzello, S.J. 1998, Selected physiological and psychological responses tolive-fire drills in different configurations of firefighting gear. Ergonom, 41, 1141-54.

Smith, D.L., Manning, T.S. and Petruzzello, S.J. 2001a, Effect of strenuous live-fire drills on


41/42

cardiovascular and psychological responses of recruit firefighters. Ergonom, 44, 244-54.

Smith, D.L., Petruzzello, S.J., Chludzinski, M.A., Reed, J.J. and Woods, J.A. 2001b, Effect ofstrenuous live-fire fire fighting drills on hematological, blood chemistry and psychologicalmeasures. J Thermal Biol, 26, 375-9.

Toner, M.M., Glickman, E.L and McArdle, W.D. 1990, Cardiovascular adjustments to exercisedistributed between upper and lower body. Med Sci Sport Exerc , 22 , 773-778.

Weafer, P. 1999, Physical demands of firefighting within a petro-chemical plant. MSc thesis,University of Surrey.

White, M.K. and Hodous, T.K. 1987, Reduced work tolerance associated with wearingprotective clothing and respirators. Am Ind Hyg Assoc J, 48, 304-10.

White, M.K. and Hodous, T.K. 1988, Physiological responses to the wearing of firefighter'sturnout gear with neoprene and Gore-tex barrier liners. Am Ind Hyg Assoc J, 49, 523-30.

Williams, B.E., Petersen, S.R. and Douglas, K. 1996, Physiological responses of trainingofficers during live fire training. Fire Eng Sept , 45-52.

Yoshida, T., Takanishi, T., Nakai, S., Yorimoto, A. and Taketoshi, M. 2002, July, The criticallevel of water deficit causing a decrease in human exercise performance: a practical fieldstudy. Eur J Appl Physiol . Retrieved July 8, 2002 fromhttp://link.springer.de/link/service/journals/00421/contents/02/ 00651/paper/s00421-002-0651-zch110.html


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Physical Capabilities of Instructors at the End of Hot Fire Training (0305) [158529]

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