Volunteer firefighters play a major role in the suppression of
bushfires across Australia. Despite this heavy reliance on
volunteer firefighters in Australia, there has been limited
research into the physical demands that they experience during
bushfire suppression. Similarly, the health and physical fitness of
these volunteers has received little research attention.
Such information can be particularly valuable in estimating the
relative strain on operational personnel. To date, research has
focused mainly on the health and fitness levels of paid structural
(US), naval (UK), and forestry (US & AUS) firefighters, and
their physiological responses during fire suppression. The physical
demands faced by Australian volunteers during bushfire suppression,
as dictated by the type of work they do on the fire ground, and
their health and fitness levels, have not been thoroughly
investigated.
For this reason, researchers from The University of Melbourne,
supported by the Victorian Country Fire Authority through the
Bushfire Co-Operative Research Centre, are conducting experiments
to evaluate the physical demands of bushfire suppression, and the
health and fitness of volunteer firefighters. The research is part
of Bushfire CRC project D2.1Firefighter health and safety led by
David Nichols of the CFA.
To investigate the physical demands of bushfire suppression, the
research is measuring volunteers’ heart rate, limb movement,
and oxygen consumption during standard fireground activities,
including unreeling and reeling fire hoses and advancing charged
hoses. To measure the health and fitness of volunteer firefighters
the research is also measuring important health indicators
including resting blood pressure, blood cholesterol and glucose
levels, and body fat levels, and cardiovascular fitness.
Measuring health and fitness
From US mortality statistics we know that the physical exertion
associated with bushfire suppression can be fatal for some
volunteers. Indeed, physical exertion was the primary contributor
in 42% of volunteer wildfire fire fighter deaths in the US during
the 1990s. Two major determinants in the risk of physical
over-exertion are the physical health and fitness of the individual
and the demands of the work or exercise being performed. For this
reason our research team is characterising the general health and
cardiovascular fitness of a group of Country Fire Authority
volunteers aged 18 to 60.
We are measuring the physical demands faced by volunteers doing
bushfire fighting. We hope that this data will provide an insight
into the level of fitness required of bushfire fighters. As a
follow up we aim to use the above data to devise a physical fitness
challenge that accurately predicts whole-body fitness for
firefighters. The plan is that this test be readily and easily
administered at fire stations. As such, the physical readiness of
volunteer firefighters can be conveniently and accurately assessed
before deployment. Finally, we are also interested in trialing a
range of strategies that we hope will counter (at least in part)
the physical stresses experienced by bush firefighters, enabling
them to sustain their efforts for longer periods on the fireground.
These interventions are likely to focus on eating and drinking
strategies before, during and after work shifts.
Feeling the heat
Previous research has shown that under normal conditions (8-29
° C, low humidity) rises in core temperature, heart rate and
energy expenditure are driven exclusively by the intensity of the
exercise. That is, the harder you work the more physiological
stress you are under. Fire fighting places additional physiological
stress on the individual, namely heat, protective clothing, and
smoke.
Bushfires occur during hot dry weather that, when coupled with
the heat of the fire itself, places a considerable amount of
thermal stress on the body. This thermal stress increases core
temperature, heart rate, and energy expenditure independent of the
work rate. To offset this heat load the body will sweat in an
attempt to cool down through evaporation off the skin. If the fluid
lost as sweat is not replaced (that is, dehydration takes place),
physiological stress is exaggerated. For instance, with less bodily
fluid there can be a decrease in blood volume, so the heart must
beat faster to deliver the same amount of blood.
Recent research also suggests that with less blood volume, there
is less blood that can be sent to the skin surface to increase
cooling, through sweat and evaporation. As such, the body’s
core temperature continues to rise. With rising core temperature,
individuals have been shown to experience muscle weakness and a
loss of balance. There appears to be a critical core temperature
which, if crossed, there is a decreased motivation to continue
working even if the individual has sufficient energy. It is
possible that this loss of motivation is the brain’s way of
stopping the heat stress inducing activity before there is serious
damage done to the body. In other words, it may be a protective
mechanism.
Each of the physiological consequences of working in the heat
are increased by the protective clothing often worn by firefighters
to protect them from radiant heat from the fire and burning debris.
Existing research suggests the protective clothing may also limit
the heat loss from the body, making it more difficult for the fire
fighter to cool down. One way that protective clothing may limit
cooling is by reducing the amount of skin exposed to the air.
Evaporation, the principal method of heat loss in hot working
conditions relies on sweat being evaporated off the skin to cool
the body. If the skin is covered by protective clothing, less
evaporation and therefore less cooling will occur.
Finally, in a smoke filled environment such as under some
bushfire conditions, exposure to carbon monoxide and other smoke
compounds may also compromise fire fighter work output. For
instance, previous research has shown that exposure to carbon
monoxide may lead to dizziness, nausea and impaired judgement,
whilst other smoke compounds may reduce lung function, reducing the
value of air that can be inhaled and exhaled.
Drink up
As can be seen, fluid loss and the resulting dehydration
accelerates rises in core temperature, heart rate and energy
expenditure. For this reason fluid replacement on the fireground is
a critical strategy for fire fighters.
The research into hydration during exercise in the heat
advocates using a carbohydrate and electrolyte (that is, salt)
beverage for optimal rehydration. The carbohydrate provides energy
which is critical for sustaining work rate over long working hours
undertaken by bushfire fighters. Further, during work in hot
conditions the body burns carbohydrates more quickly, reducing the
sustainable energy supply. Provided the carbohydrate content is
less than 10 per cent, such as in a number of commercially
available products, the fluid passes through the digestive system
and reaches the muscles as fast as water. The inclusion of
electrolytes, particularly sodium, helps maintain the
“drive” to continue drinking, helps minimize urinary
fluid losses post-shift, and therefore maintains body fluid
volumes, more effectively than water.
The limited research into fluid loss during fire fighting in
bushland areas suggests that fire fighters do not adequately
replace their fluid loss even when under instruction to drink
frequently. Whether this is a function of the type of drink
prescribed or the culture of the fire fighter is unclear.
Research for all fire agencies
It is hoped that through this research, the CFA will gain a
greater insight into the physical demands experienced by their
volunteers during bushfire suppression. Through the Australasian
activities of the Bushfire CRC this information will be valuable to
other fire agencies in Australia and New Zealand. It also is
anticipated that the information collected will assist in the
identification and development of strategies (including diet and
hydration) to assist volunteer firefighters to work safely and
effectively on the fire ground.
Fast Facts
Bursting
A bout of fast rake hoeing along a fireline expends as much
energy as running at 12km/h or an intense game of squash.
Switching
Increases in heart rate and blood flow that accompany intense
fire ground work can also:
- narrow one’s attention, which may impact upon decision
making
- make it difficult to produce fine movements where hands or
other limbs need to be steady.
By Brad Aisbett, from the Department of Physiology,
University of Melbourne. Brad is a part of the Bushfire CRC Project
Firefighter Health and Safety.
This article appears in Fire Australia, Winter 2006. Fire
Australia is a joint publication of the Bushfire CRC, the
Australasian Fire Authorities Council and the Fire Protection
Association of Australia.
