Firefighters must remain adequately hydrated, not only for their safety but for the safety of those they assist. This article dives into the science behind hydration.
Firefighters are frequently exposed to high
levels of heat, making proper hydration a very important topic within their
line of work. Not to mention, firefighters wear layers of protective clothing
and carry heavy equipment while exposed to these high temperatures. Firefighters
are recommended to begin work within a state of euhydration (water in the body
is sufficient to meet physiological demands). In this state, fluid within the
body will maintain an appropriate body temperature, deliver nutrients, and
assist in maintaining electrolyte balance (4). For every 1,000 mL of fluid
deficit, a heart rate can increase eight beats per minute, rectal temperature
can increase by 0.3°C per minute, and cardiac output can decrease (4).
Rehydration is best completed over a
period of 12–24 hr; however, this is not always possible due to prolonged
firefighting efforts like large wildfires. To maximize absorption of fluid
intake, research has shown that consuming water with carbohydrates and/or
sodium chloride can affect absorption of fluids. This is especially true
following a call when rapid and complete rehydration is desired (4).
One should keep in mind though, that too much
water is just as dangerous as not enough water consumption. Hyponatremia or
“water intoxication” can be caused by overconsumption of hypotonic fluids,
excessive loss of sodium through sweat, and extensive sweating while ingesting
low-sodium fluids. To minimize the chances of hyponatremia, sport drinks
containing 20 mEq sodium (460 mg per L of fluid) are recommended during efforts
lasting 60 to 90 min in duration (1).
Monitoring hydration status is
important to ensure optimal performance. Good methods should be sensitive and
accurate while being practical from a time, cost, and technical standpoint.
Urine color measurement, urine specific gravity, and monitoring pre- and post-incidence
body weights (BW) are common methods for monitoring hydration. Although each
method has its limitations, when used in combination with a second or even
third method, they are effective and accurate in determining current hydration
Urine color measurement is the most
basic method which can be monitored by an individual without additional
equipment or testing supplies. The general recommendation is if one’s urine is
the same color as diluted lemonade (1) and produced in medium to large volumes,
the person is well hydrated. If urine is dark-colored with an odor and produced
in small volumes, the person is dehydrated (4). However, one has to be aware
that certain dietary compounds can affect the color and odor of urine (e.g., B
vitamins, beets, and certain other foods and supplements).
To ensure adequate rehydration,
consider monitoring pre- and post-call BW. For every one pound of BW lost, 20
ounces of fluid are recommended. It is also advisable to avoid alcoholic and
caffeinated beverages during periods of rehydration to prevent possible
diuretic effects. Salting meals can be an appropriate recommendation to
replenish lost sodium chloride in sweat (4).
before, during, and after your work shift, while monitoring your hydration
status through urine color. Most firefighters need 4 – 6 L of water per day to
stay hydrated (3).
sustained efforts, consume a combination of sports drinks and water to provide
adequate fluids and maintain blood sugar for sustained energy. Consuming cool,
flavored beverages has been shown to increase fluid intake as compared to plain
water consumption (2).
early and drink often because thirst is not a good indicator. The body is
already approximately 1% dehydrated by the time one notices the thirst
- Campbell, BI, and Spano, MA. Fluids. In: Seebohar, B. (Ed), NSCA’s Guide to Sport and Exercise Nutrition, Champaign, IL: Human Kinetics; 71-86, 2011.
- Cuddy, JS, Ham, JA, Harger, SG, Slivka, DR, and Ruby, BC. Effects of an electrolyte additive on hydration and drinking behavior during wildfire suppression. Wilderness and Environmental Medicine 19(3): 172-180, 2008.
- Domitrovich, J, and Sharkley, B. Heat Illness Basics for Wildland Firefighters. Tech Tip 1051-2316P-MTDC. U.S. Department of Agriculture, Forest Service, Missoula Technology and Development Center; 8, 2010.
- Dunford, A, and Sports, Cardiovascular, and Wellness Nutritionist Dietetic Practice Group. Fluids, electrolytes, and exercise. In: Sports Nutrition: a practice manual for professionals (4th ed.). American Dietetic Assn; 94-115, 2005.
About the Author
Katie Miller has a BS in Criminal Justice which she used to start her professional career as a police officer in Mississippi. Katie later received a BS in nutrition/dietetics and went on to complete a dietetic internship through Meredith College including a sports nutrition rotation at North Carolina State University. Now at the NSCA, Katie works as a nutrition consultant and tactical athlete coordinator within the NSCA’s Performance Center where she counsels tactical athletes on weight management and tactical performance.