LEC2,3: Firefighting

Question 1

What is the average VO2 of firefighters during a stair climb task in FPE with extra weight of two hose lengths in a high-rise pack

Williams-Bell et al, Applied Ergonomics (2010)

Answer 1

~35 ml/kg/min Body Mass

Question 2

What does having an RER > 1.0 indicate?

Answer 2

RER = 0.7 indicates that fat is the primary fuel source.
RER = 1.0 indicates a mix of carbohydrates and fats being used for energy.
RER > 1.0 indicates that carbohydrates are the primary source of energy.

An RER value greater than 1.0 suggests that the individual is likely in a high-intensity, anaerobic state (around threshold) where they are producing more carbon dioxide and consuming more oxygen

Question 3

What was the average duration of the stair climb + descent?

Williams-Bell et al, Applied Ergonomics (2010)

Answer 3

10:22 (min:s) with a range
from 8:14 to 14:11

Question 4

What was the average number of floors climbed while consuming 55% of a typical air cylinder

Williams-Bell et al, Applied Ergonomics (2010)

Answer 4

20 ±2.5 flights
(range 14.5–23 flights)

Question 5

There is a
(__blank__) relationship between VO2 and work time

Answer 5

inverse

Question 6

There is a (blank) relationship between intensity and duration

Answer 6

inverse

Question 7

What is the oxygen demand of structural firefighting?

Answer 7

2.5-3.0 L/min
~10 METS

Question 8

What is Lactate Stacking?

Answer 8

Accumulation of lactate in the muscles during prolonged or high-intensity exercise

Study of the firefighting test revealed that mean post-circuit blood lactate values averaged 16 mmol/L (Deakin et al. 1996).

Petersen et al. (2000) reported that blood lactate levels at the end of work averaged 15.5 mmol/L

Question 9

What does Firefighting gear consist of?

Answer 9

1. Fire Protective Ensemble (FPE)
2. Self Contained Breathing Apparatus (SCBA)

Question 10

What is the metabolic cost of walking while carrying 6kg of weight?
1. on the back
2. in the hands
3. on the legs

Abe et al (2004)

Answer 10

All three are negative parabolas (U) with the lowest point at approximately 3 mph

Weight on the legs has the most metabolic cost. Weight in the hands and on the back are at similar positions, lower than weight on the legs. Weight on the back has the least metabolic cost

Further from the centre of mass increases the metabolic cost

Question 11

What is the Hobbling Effect?

Duggan (1988); Teitlebaum & Goldman (1972)

Answer 11

Increase is beyond the effects of weight alone

Multiple clothing layers increase energy expenditure by ~2.4% per additional layer

Mostly due to friction between layers

Question 12

A more realistic estimate of energy expenditure will account for the additional (blank) and the (blank)

Answer 12

weight, hobbling effect

Question 13

What does Raven et al (1977) state about physical demands of firefighting?

Raven et al (1977)

Answer 13

SCBA alone reduced exercise time by ~21% (747 s without SCBA vs 590 s with SCBA)

Question 14

What does Louhevaara et al (1995) state about physical demands of firefighting?

Louhevaara et al (1995)

Answer 14

Protective ensemble reduced exercise time by ~27% carrying BUT NOT breathing on SCBA. Similar physiological maxima (VO2max etc)

Question 15

What does Gledhill and Jamnik (1992) state about physical demands of firefighting?

Gledhill and Jamnik (1992)

Answer 15

Generally considered to reduce “max” performance by 20 – 30%

Question 16

What does Eves et al (2005) state about physical demands of firefighting?

Eves et al (2005)

Answer 16

1. ~5% decrease in VO2max due to load of SCBA
2. ~13% decrease in VO2max due SCBA regulator

Question 17

What is personal protective equipment
in firefighting used for?

Answer 17

Designed to protect the worker from intense heat, flame and exposure to chemicals

Generally prevents heat loss in thermo-neutral environment
- heat from muscle contraction is trapped and increases body temperature
- trapped heat and moisture create an unfavorable micro-environment

We gain heat when the ambient temperature is greater than body temperature (e.g., in a fire)

Question 18

What is personal protective equipment
in firefighting made of?

Answer 18

Multiple Layers =
↑ Insulation
↓ Vapour Permeability
Face cloth, thermal barrier, moisture barrier, outer shell

Question 19

What is normal range of core temperature?

Answer 19

37 - 40 degrees

Question 20

What attributes to thermal stress in firefighting?

Answer 20

1. Heat from the environment (e.g., radiant heat from fire)
2. Heat from demanding physical exercise trapped by FPE

Question 21

What is Uncompensable Heat Stress (UHS)?

Answer 21

Occurs when the evaporative heat loss required to maintain a thermal steady state (Ereq) exceeds the maximal evaporative capacity of the environment (Emax)

When Ereq > Emax, Heat Strain Index > 1 (Uncompensable)

Question 22

What is Compensable Heat Stress (CHS)?

Answer 22

Heat loss mechanisms that the body can effectively regulate or compensate for to maintain a stable core body temperature

When Ereq < Emax, HIS < 1 (Compensable)

Question 23

What are the effects of the SCBA on ventilation?

Answer 23

1. The SCBA imposes a significant RESISTANCE to ventilation during heavy exercise
2. At about 80-100 L/min the respiratory muscles must generate about 1.5 times the pressure to ventilate the same volume with the SCBA
3. more effort is required to produce any level of ventilation (e.g., 80 L/min) AND maximal ventilation is reduced

Almost all resistance is on expiration, not inspiration

Question 24

What is the cardiopulmonary strain during structural firefighting?

Answer 24

1. Increased metabolic demand leads to higher HR and VE
2. Thermal strain increases VE (and rate of air use)

Question 25

Fractionation: treadmill

Answer 25

1. Control = ~13 mlO2/kg
2. Full FPE = ~22 mlO2/kg
3. Helmet = ~14 mlO2/kg
4. SCBA = ~10 mlO2/kg
5. Boots = ~89 mlO2/kg
6. Clothing= ~33 mlO2/kg

Question 26

Fractionation: bench stepping

Answer 26

1. Control = ~15mlO2/kg
2. Full FPE= ~20 mlO2/kg
3. Helmet= ~28 mlO2/kg
4. SCBA = ~11 mlO2/kg
5. Boots = ~72 mlO2/kg
6. Clothing = ~36 mlO2/kg