Introduction

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

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 status (1). 

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).  

Practical Application: 

1. Hydrate 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).
2. During 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).
3. Drink 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 sensation (3).

Resources

1. 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.
2. 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.
3. 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.
4. 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.