The myth of drinking water

Firefighter on the Shep Canyon fire in South Dakota, September 6, 2011

Above: Firefighter on the Shep Canyon fire in South Dakota, September 6, 2011. Photo: Bill Gabbert/Wildfire Today.

After reading our excerpt and later the full document from the the Serious Accident Investigation Factual Report  for the hyperthermia fatality on the CR 337 fire in Texas, we heard from Dr. Brent Ruby, who has completed studies on this exact issue, even having studied wildland firefighters while they were working on fires. In one of his studies he was monitoring a wildland firefighter outfitted with a core temperature monitor, an ambient temperature sensor, and a special Camelback hydration system that monitored his water intake. This firefighter experienced a heat-related illness, heat exhaustion, and had to be evacuated off the fireline by a helicopter. That was a terrible thing to happen to a firefighter, and I’m sure the researchers thought the same thing, but it was probably a once in a lifetime cornucopia of incredibly useful data. Dr. Ruby sent us this message, reprinted here with his permission:

I was bothered by the findings of the CR337 fatality report from the investigation team. There are issues within this case that are very similar to a published heat exhaustion case study we published recently (Wilderness and Environmental Medicine 22, 122-125, 2011, In this report, we document drinking behavior, activity patterns, skin and core temperatures in a subject that suffered heat exhaustion and required evacuation. The lessons learned from this research clearly indicate that the best protection against a heat injury is reducing work rate. [*the abstract from the study is below]

Aggressive hydration strategies are over-preached and may provide a false sense of protection. It should be emphasized that the autopsy report as described in the fatality report indicated no signs of dehydration or electrolyte imbalance. I have tried to push these concepts to crews and safety officers when I get a chance to speak to them at meetings. I was bothered by this fatality knowing that it is seemingly directly linked to some of our research findings. I have tried to emphasize this to anyone that will listen in the world of wildfire.

You can certainly review our website to gain a better understanding of the publications we have done from research with the WLFF We have a great deal of physiological data, hydration, energy demands of the job, importance of supplemental feedings, etc. from all our work over the years. This peer reviewed research provides objective, scientific evidence that can be used to to change or influence policy to enhance safety on the line.

Let me know if you have any questions.

Regards, Brent Ruby

Brent C. Ruby, Ph.D., FACSM

Director, Montana Center for Work Physiology and Exercise Metabolism, The University of Montana

* Here is the abstract from the study:

Wilderness Environ Med. 2011 Jun;22(2):122-5.

High work output combined with high ambient temperatures caused heat exhaustion in a wildland firefighter despite high fluid intake.

Cuddy JS, Ruby BC.

Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, Missoula, MT 59812-1825, USA.

The purpose of this case study is to examine the physiological/behavioral factors leading up to heat exhaustion in a male wildland firefighter during wildland fire suppression. The participant (24 years old, 173 cm, 70 kg, and 3 years firefighting experience) experienced heat exhaustion following 7 hours of high ambient temperatures and arduous work on the fire line during the month of August. At the time of the heat-related incident (HRI), core temperature was 40.1 °C (104.2 °F) and skin temperature was 34.4 °C (93.9 °F). His work output averaged 1067 counts·min(-1) (arbitrary units for measuring activity) for the 7 hours prior to the HRI, a very high rate of work over an extended time period during wildfire suppression.

In the 2.5 hours leading up to the heat incident, he was exposed to a mean ambient temperature of 44.6 °C (112.3 °F), with a maximum temperature of 59.7 °C (139.5 °F). He consumed an average of 840 mL·h(-1) in the 7 hours leading up to the incident and took an average of 24 ± 11 drinks·h(-1) (total of 170 drinks). The combined effects of a high work rate and high ambient temperatures resulted in an elevated core temperature and a higher volume and frequency of drinking than typically seen in this population, ultimately ending in heat exhaustion and removal from the fire line.

The data demonstrate that heat-related incidents can occur even with aggressive fluid intake during wildland fire suppression.

Unfortunately, even though Dr. Ruby’s research is funded by taxpayers through the National Institutes of Health, the National Science Foundation, and the Department of Defense, taxpayers are blocked from seeing the full results unless they pay a fee to the privately owned company that published the paper. We have written before about the results of taxpayer-funded wildfire-related research being held hostage by private companies. Dr. Ruby told Wildfire Today that he will send a copy of his paper to individuals that write to him at brent dot ruby at mso dot umt dot edu

The combined information about the fatality of Caleb Hamm on the CR 337 fire and Dr. Ruby’s study on wildland firefighters, is shocking. From the abstract, again:

The data demonstrate that heat-related incidents can occur even with aggressive fluid intake during wildland fire suppression.

Working on a wildfire on a hot day can lead to heat exhaustion and hyperthermia, and can be fatal EVEN IF a person drinks plenty of water and is not dehydrated.

Symptoms and prevention

We asked Dr. Ruby for more information:

Exertional hyperthermia occurs when the metabolic heat production from hard work overwhelms the bodies ability to off load it to the environment. This unloading can be blocked by clothing and/or slowed due to high radiant heat from the sun or an adjacent fire.

The basic symptoms of heat exhaustion are commonplace and can include profuse sweating, weakness, nausea, sometimes vomiting, lightheadedness, headache and sometimes mild muscle cramps.

The best approach [to prevent heat exhaustion and hyperthermia] is to know thyself and thy physical limits. Establishing a pace schedule that allows temperature to come back down in between periods of work that result in a rise in temperature. The factors of importance are pace, fitness level for the task at hand, hydration behaviors and simultaneously electrolyte concentrations in the blood.

It is important for wildland firefighters to drink plenty of water, but this will not, by itself, totally eliminate all chances of heat-related illness.

Be careful out there.


UPDATE  October 27, 2011:

Dr. Ruby sent us the following list of other publications on similar topics that are in peer reviewed journals. I assume that most of them are not available to the public (don’t get me started on that again!) unless you pay the ransom fees at the private companies, or send a message to Dr. Ruby:  brent dot ruby at mso dot umt dot edu

Dr Ruby articles


UPDATE October 28, 2011:

The U.S. National Library of Medicine has an excellent article about heatstroke, which can follow heat cramps and heat exhaustion and is life-threatening. The article includes causes, symptoms, first aid, what not to do, when to call 911, and prevention (including “avoid exercise or strenuous physical activity outside during hot or humid weather”. Good luck with that one, firefighters.)

Typos, let us know HERE, and specify which article. Please read the commenting rules before you post a comment.

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Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire.

13 thoughts on “The myth of drinking water”

  1. Damn… I should have read Bill’s post first before replying… damn near duplicate.

    I guess that means there is still some “Hotshot Corporate Knowledge” floating around… LOL.

    Filson is actually a good material for two-way insulation.. and when it is wet with sweat, it provides evaporative cooling……..

    1. All of your comments are great, but ignoring what happened in my son’s case. He was LEFT ALONE after he stated he was hot and had a headache. After being left alone, he fell in a ravine, where he was MUCH LATER, found. For all intents and purposes, he died in that ravine. He did not die from lack of water. Please read the whole report, you will see page 8, clearly states he told his superior he felt hot, and had a headache. Then see page 21, clearly states signs NOT VERBALLY communicated by Hamm. Seems like a contradiction, does it not????

      1. There is no cover up. He was found were he was left, curled up just a couple minutes after he sat down. I am deeply sorry for your loss. Its a loss for all of use. We will never forget.

  2. I see Jerry’s comment, ..”if a person doesn’t perspire the person will overheat.” and think that if a person’s perspiration can’t evaporate that person will also overheat.
    I believe there are other variables out there to consider. 1) Modern wildland packs have morphed over the years, first into comfortable ergonomic configurations then, because of all that padding, greater load capacity configurations. That padding could prevent the body’s largest organ, the skin, from cooling the body down properly. That extra load-carrying capacity gets utilized and burdens firefighters with more weight than we used to carry “back in the day”.
    2) Staying in a motel means: a temperature controlled environment non-conducive to acclimatization, fast and fatty foods non-conducive to good nutrition, and access to super-caffienated beverages (or other types), non-conducive to healthy body function.
    3) Recent studies into the increased incidence of rhabdomyolisis among firefighters have pointed to more suspects, beyond the popular super-caffienated drinks, like OTC drugs, dietary muscle building supplements, etc. that weren’t utilized much just a decade or so ago.
    My point is simply that a cornucopia of factors may weigh in and that we should guard against getting too focused on any solitary causal factor.

    1. Good points, Safety Don. WAY back in the day, before packs, the only gear we carried on the El Cariso Hot Shots was a web belt with canteens, a fire shelter, and a Filson Tin Cruiser vest which we bought with our own money. The Cruiser vest, by the way, is still sold, but at many times the cost that we paid back then. We used the numerous pockets in the vest for our lunch, gloves, compass, snacks, another layer when it was cold, etc. But then a directive came down from On High forbidding the vest, because it would interfere with the dispersion of body heat — which made sense then, and still does now.

    2. Safety Don,

      You made some excellent real world points… weight, acclimatization, and those damn energy drinks. They are factors in many of the “heat related” issues being reported lately. I’m sure more emphasis will happen eventually.

      When I started (on a Hotshot Crew like many of you), we carried 3- 4 qts of water on a lightweight surplus Vietnam era military web belt w/ a small pouch to carry supplies (headlamp, batteries, trashbag/poncho); a small and lightweight fire shelter in a bright orange case; and a filson vest.

      In the pouch on the vest, you carried whatever you could, but it wasn’t a lot except for an OLD c-rat or k-rat.

      Total gear weight “way back then” was about 18-20 lbs (including tool, unless you were a sawyer).

      Nowadays, seems the average Hotshot Pack weighs 40+ pounds (minus the tool) and is filled with “stuff” not really needed on the fireline.

  3. Bill,

    Excellent article. This is the type of info that should be posted and shared throughout our various internal and external communication circles also… ie- Fire Management Today.. Safety Alerts.. emails.. etc.

    Thanks for giving the issue a voice.

  4. Jerry, You are exactly right on all accounts! We have some new research regarding acclimatization to the heat and we are also making strides on identifying potential blood markers that may predict who is able to cope and/or less able to cope with work in the heat. Fitness is one of the best protectors/predictors of heat resilience. This is especially true with a crew. Fitness must be a big priority. Jerry – your field observations line up precisely with all the research! Brent

  5. Not knowing the exact circumstances of the situation that was involved with the firefighter who was overcome by heat we can only sumize.
    As a former Zigzag Hotshot crew member myself and everyone else realizes that water intake alone is not the only thing to sustain a firefighter in 100 plus degree weather. Proper conditioning is at least as important as well as taking required breaks, pacing ones self and not over hydrating. Some people react to extreme heat better then other people. If a person does not perspire the person will overheat. Weight is also an important factor. Equally important is having a crew supervisor who is in touch with the crew members and how they are coping with the extreme heat on the fireline.

  6. I like the idea of using scientific data from peer reviewed research to update Safety Officer training and or any Annual Refresher coursework. It is all too often that subjective bias is implanted into policy with little to no regard for the science. I do think that science has done a poor job at translation to the outside world. However, our research center ( seeks to change these rules. Our science is meant to be accessible and applicable to multiple end users. I am happy to report on this or any other of our research at upcoming safety summits, crew meetings, etc.

    1. Thanks, Brent, and I hope some groups take you up on your offer to present the information at meetings and conferences.

  7. Good job on bringing this issue to the forefront – critical for folks working in extreme heat like the SW and Intermountain areas with temps over 100F; This article and Dr. Ruby’s paper and other work should become a mandatory part of every Safety Officer class, and part of the RT-130 Annual Refresher training class for everyone.


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