Fall 2002 Missoula Technology and Development Center No. 6

0251–2837–MTDC

• Energy requirements• Energy supplements• Nutritional strategies• Micronutrients• Immune function

Health & Safety ReportWildland FirefighterWildland FirefighterWildland Firefighter

In this issue:

BackgroundThis report, the sixth in aseries, reviews activities relatedto the Missoula Technology andDevelopment Center (MTDC)project on wildland firefighterhealth and safety. The projectfocuses on three main areas:

Work, Rest, and FatigueDevelopment of an objectiveapproach for the determina-tion of work/rest standardsand recommendedassignment lengths forcrews and overhead.

Energy and NutritionImprovement of the energyintake, nutrition, andimmune function of wildlandfirefighters.

Fitness and Work CapacityImplementation of workcapacity and medicalstandards and improvementof the health, safety, andproductivity of firefighters.

Energy andNutritionThis report focuses on energyand nutrition, and theirinfluence on health andperformance. MTDC reviewedthe relevant literature,interviewed firefighters, metwith contracting officers, andconducted field studies. Thesuggestions that follow providea basic approach to wildlandfirefighter nutrition thatensures adequate energy andnutrients, supports immunefunction and health, maintainscognitive function, and delaysfatigue during arduous wildlandfirefighting. Our field studiescorroborate existing research,such as that found in the

document, Military Strategiesfor Sustainment of Nutritionand Immune Function in theField (published by theInstitute of Medicine of theNational Academy of Sciences,National Academy Press,Washington, DC, 708 pp. 1999).

The featured topic of this reportoutlines basic recommenda-tions for feeding the wildlandfirefighter. The research sectionprovides documented supportfor the recommendations,including the results of recentfield studies on wildlandfirefighters. The riskmanagement section details theproblems associated with lowblood glucose (hypoglycemia).The field notes section providesadditional food for thought.

A firefighter samples his blood glucose level during a study of the effects ofcarbohydrate supplementation (page 6).

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Featured Topic

Feeding theWildland Firefighter

Recent research has identifiednutritional strategies that willimprove the health, safety, andproductivity of wildlandfirefighters. The right foodsources, properly timed,provide energy and nutrientsthat help sustain work outputand maintain the function ofthe immune system.Supplemental high-energyfoods delay fatigue and enhanceimmune function whilemaintaining the firefighter’sability to think and makedecisions during periods ofhard work. This report outlinessimple strategies formaintaining health, safety, andperformance during prolongedperiods of arduous work.

Energy

Research by the University ofMontana Human PerformanceLaboratory and the MissoulaTechnology and DevelopmentCenter has demonstrated theenergy demands and energyintake of wildland firefighters.In a recent field study (Rubyand others 2002), malefirefighters burned an averageof 4,758 kilocalories a daywhile they consumed only4,068 kilocalories. The dailycaloric deficit of 690kilocalories results in a 1.25-kilogram (2.76-pound) weight

loss over the course of a 14-dayassignment. Female firefightersburned an average of 3,550kilocalories per day, whileconsuming 3,222 kilocalories,for a daily deficit of 328kilocalories. They lost 0.6kilograms (1.3 pounds) of bodyweight in 14 days. This energydeficit could result insignificant weight loss,including loss of lean bodyweight. When energy intakefalls short of requirements, thebody derives needed energyfrom muscle tissue. This loss oflean tissue will increase thelikelihood of fatigue and couldreduce the ability of afirefighter to perform arduouswork.

The study by Ruby and othersshows that some malefirefighters may require over6,000 kilocalories of food daily,while some females mayrequire more than 5,000kilocalories during a long, hardshift. The meals provided in firecamp are planned to meet thecaloric demands of wildlandfirefighting. Computerizednutritional analysis of themeals yields a daily total of5,800 kilocalories, but thefirefighter must eat all the foodprovided to receive all 5,800kilocalories. The computeranalysis also indicates thatmost meals exceed dietaryrecommendations for fat andwere somewhat low innutritional carbohydrates.Complex carbohydrates (suchas potatoes, corn, rice, beans,and whole-grained breads andpasta) provide energy while alsosupplying needed nutrients andfiber.

Table 1—The performance diet.

Approach these levels by:

• Increasing the intake ofcomplex carbohydrates(potatoes, corn, rice, beans,and whole-grained breadsand pasta) and fruit (fresh,dried, or canned)

• Maintaining the usual levelof fat, emphasizing healthyfats in nuts, seeds, and oilswhile minimizing saturatedand hydrogenated fats

• Consuming high-carbohydrate energysupplements during andimmediately after work

Percentof daily

Nutrient calories

Carbohydrates 60Fat 25Protein 15

DietaryRecommendations

Studies of endurance athletes,soldiers, and wildlandfirefighters support the need fora diet that is high incarbohydrates and low in fat.Carbohydrates help maintainimmune function, while toomuch fat may degrade thefunction of the immune system,increasing the risk of upperrespiratory and other healthproblems. We recommend theperformance diet for wildlandfirefighters and for everyonewho wants to engage in vigor-ous physical activity (table 1).

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Energy Supplements

Solid and liquid carbohydratesupplements provide muscleenergy and help keep youthinking clearly while helpingto maintain or even improveimmune function.

Solid Supplements

During Work—The energy barsused by endurance athletes arean excellent way to supplementenergy between meals.Consuming one 250-kilocaloriebar between breakfast andlunch and one between lunchand dinner provides anadditional 500 kilocalories ofenergy each day. Lessexpensive candy bars are areasonable substitute forenergy bars and have provenmore palatable in taste tests.However, candy bars containmore fat than energy bars, andthe chocolate in some barstends to melt when exposed toheat.

After Work—Studies show thatcarbohydrate replacement (inliver and muscle) is most rapidduring the 2 hours immediatelyafter the work shift. Firefightersshould be provided with at least500 kilocalories of energyreplacement in the 2 hoursafter work. Carbohydratesupplements will ensure thefirefighter’s ability to recoverand be ready for work thefollowing day. Liquidcarbohydrate sources areabsorbed faster than solidsupplements; they aidrehydration and may speedrecovery. Grape and cranberryjuices are high in carbo-hydrates. Ingesting someprotein (1 gram of protein per 4grams of carbohydrates) within2 hours after work may reducemuscle stress and accelerate

replacement of muscleglycogen. Sports recoverydrinks that provide this ratio ofcarbohydrates and protein areavailable in powdered form.

Combining the energysupplements consumedbetween meals with those takenafter work yields an additional1,000 kilocalories of energy.

Liquid Supplements

Firefighters need to consumefluids before, during, and afterwork to maintain hydration.Carbohydrate/electrolytebeverages (C/E or sportsbeverages) provide fluid, energy,and electrolytes needed duringprolonged work. Sportsbeverages promote increasedfluid intake and help maintainblood sugar during arduouswork. The electrolytes helpconserve fluid that mightotherwise be lost in urine.

During Work—MTDCrecommends that one-third toone-half of fluid needs be metby drinking a sports beverage.Because firefighters need about1 liter (about 1 quart) of fluidfor each hour of work, they willneed 4 to 6 quarts of sportsbeverage for a 12-hour shift.Firefighters can be givenpackets of dried drink mix thatthey can mix as needed. A 3- to

Nutrients—You can get thevitamins, minerals,antioxidants, and immune-friendly foods your body needsby eating the recommendednumber of servings of fruits andvegetables. For the prolongedarduous work of firefighting,you should try to eat fourservings of fruit and fiveservings of vegetables daily(one serving is about the size ofyour fist). An apple or orange isone serving, as is 1¦2 cup ofapricots, dried fruit, or fruitjuice. Two and one-half cups ofvegetables will meet the dailyrequirement. Select dark leaflettuce and a variety ofvegetables (such as green beansor carrots).

Protein—Endurance andstrength athletes need 1.2 to1.6 grams of protein perkilogram of body weight daily.Fire camp meals provide thismuch protein. Excess proteinis not recommended forfirefighters because it cancompromise carbohydrateintake, increase fat intake,and lead to chronic dehydra-tion in active individuals.

Antioxidants—In addition toan increased need forvitamins and minerals,firefighters need increasedlevels of antioxidants (includ-ing vitamins C and E,minerals zinc and selenium,and phytochemicals) tocounter the oxidative stressassociated with high levels ofenergy expenditure, exposureto smoke, and sunshine.Research shows that themost effective way to achievethe benefits of nutrients is toconsume nutritious food, notvitamin/mineral supplements.

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5-percent carbohydratesolution (30 to 50 grams ofcarbohydrates per liter of water)is well tolerated during work inthe heat. Four liters of waterwith 200 grams ofcarbohydrates provides 800kilocalories of energy. Thebalance of fluid needs shouldbe met by consuming water atregular intervals (about 8ounces every 15 minutes).Drinking a sports beverage andwater is the safest way tomaintain hydration whileproviding additionalcarbohydrates to maintainblood glucose.

After Work—To rehydrate andto replace muscle and livercarbohydrate stores,firefighters should consumeabout 2 quarts of a sportsbeverage in the 2 hoursimmediately after work. Ahigher carbohydrateconcentration (10 to 15percent) is tolerated after work,when the crew is traveling orwaiting for transport. Theelectrolytes in the drink helpretain the needed fluid. Thisapproach ensures fluidreplacement, muscle recovery,and optimal replacement ofmuscle carbohydrate stores(muscle glycogen).

The liquid energy consumedduring and after work providesan additional 1,000 kilo-calories of energy.

Energy Summary

The energy consumed in meals,combined with solid and liquidcarbohydrate supplements,provides the fuel to powerfirefighters during long shiftsand extended assignments(table 2).

Questions and Answers

Q. Has one sports beveragebeen proven to be moreeffective than the others?

A. No. Research has notdemonstrated meaningfuldifferences amongcompeting products. Theimportant point is to getfluid, carbohydrates (50grams per liter), andelectrolytes in yoursports beverage.

Q. What about the so-called“energy” drinks? Are theysuitable for hydration?

A. No. Most of the beveragessold as energy drinkscontain morecarbohydrates (80 to 120grams per liter) than areneeded during work (30 to50 grams per liter). Thehigh concentration ofcarbohydrates could slowthe rate at which fluid isabsorbed from theintestines. In addition,most of these productscontain caffeine (adiuretic), guarana,ephedra, or otherstimulants that couldinterfere with the body’sability to withstand heatstress.

Table 2—Daily energy sources.

ApproximateEnergy source kilocalories

Meals 4,000

Solid supplements 1,000

Liquid supplements 1,000

Total energy more than 6,000

Recommendations forFirefighter Nutrition

• Eat more complex carbohydrates(potatoes, corn, rice, beans andwhole-grained breads and pasta).

• Eat fatty foods (steak, cheese) andadded fats (margarine,mayonnaise) in moderation.

• Consume supplementalcarbohydrate energy (energy orcandy bars) between meals.

• Consume one-third to one-half ofdaily fluids in the form of acarbohydrate/electrolyte sportsbeverage. Carry enough powdereddrink mix for 4 to 6 quarts ofbeverage.

• Consume solid and liquid energysupplements immediately afterthe work shift.

• Eat four servings of fruits and fiveservings of vegetables daily (aserving is a fist-sized portion).

• Consider taking a daily vitamin/mineral supplement if dietaryrecommendations cannot be met,when environmental conditions(such as smoke) are severe, orwhen appetite or food availabilitylimits energy and nutrient intake.

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Q. Has one energy bar beenproven to providesuperior results?

A. No. Studies have notdemonstrated differencesin athletic performance orimmune function,regardless of the type ofcarbohydrates, or thebalance of carbohydrates,protein, and fat in theproduct.

Q. Can candy bars be used toprovide solid energysupplementation?

A. Yes, but keep severalpoints in mind. Candybars contain more fatthan energy bars. Thechocolate in candy bars

melts in the heat. Somecandy bars containpeanuts that could triggerallergic reactions in asmall number offirefighters. MTDCrecommends a mix ofcandy and energy bars.Consume the chocolatebefore temperatures rise.

Q. Does a firefighter needadditional protein?

A. No. The protein providedin the meals is more thanadequate, even for thearduous work offirefighting. Recentstudies suggest thatingesting some protein (1gram of protein per 4grams of carbohydrates)

within 2 hours after workmay reduce muscle stressand acceleratereplacement of muscleglycogen.

Brian Sharkey, Ph.D., MTDC; BrentRuby, Ph.D., and Carla Cox, R.D.,both with the University of MontanaHuman Performance Laboratory.References are available from BrianSharkey at: bsharkey@fs.fed.us

This report first appeared as anMTDC Tech Tip, Feeding theWildland Firefighter (0251–2323–MTDC), August 2002.

An electronic copy of the Tech Tipis available on the Internet at theaddress: http://www.fs.fed.us/cgi-bin/enter.pl?link=/pubs/htmlpubs/htm02512323/

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Research

Carbohydrates andWork Rate

Our laboratory at the Universityof Montana has demonstratedthat the total energyexpenditure of extendedwildfire suppression mayexceed 6,000 kilocalories/day(Medicine and Science inSports and Exercise 34(6):1048–54, 2002). The purpose ofthis study was to determine theeffects of supplementalcarbohydrate (CHO) feedings onself-selected work rates duringextended arduous wildland firesuppression. Subjects includedwildland firefighters (n = 20hotshots) during two wildfiresin Idaho and Oregon. Subjectsconsumed 200 milliliters (6.8ounces) per hour of a 20-percent maltodextrin solution(40-gram carbohydrate) or aplacebo (PLA) drink in acounterbalanced crossoverdesign and were allowed todrink water freely during theday. Blood samples werecollected at 2-hour intervalswith an automated glucometer.The self-selected hourly workrate was determined usingaccelerometers as establishedby Heil (Applied Ergonomics33: 405–13, 2002). Data wereanalyzed using a priori plannedcomparisons across trials.

During the 20-percentcarbohydrate trials, bloodglucose (millimoles) wassignificantly higher

immediately before lunch, afterlunch, and after shift (figure 1).

The self-selected work rate wassimilar across trials during theinitial hours after breakfast,but was significantly differentlater in the morning (mean

To convert millimoles tomilligrams per deciliter dividemillimoles by 0.0555; forexample:

6 millimoles =108 milligrams/deciliter

work rate 4 to 6 hours afterbreakfast: CHO=58,088,PLA=40,191 activity counts/hour). Work rate was alsosimilar across trials during theearly hours after lunch but wassignificantly different later inthe afternoon (mean work rate4 to 6 hours after lunch:CHO=64,172, PLA=47,528activity counts/hour, figure 2).

The results indicate thatcarbohydrate supplementsmaintain blood glucose andwork rate between meals. With

Figure 1—Changes in blood glucose levels during work performed after breakfastand lunch.

Figure 2—Average activity counts in the hours after lunch (PLA = placebo, CHO =carbohydrate drink).

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illim

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= Significant difference between groups

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carbohydrates, workers selecteda higher work rate, as indicatedby the activity monitors. Theeffects were most pronounced 4to 6 hours after breakfast andlunch. Although the work ratefor wildland fire suppression ismoderate, the long work shiftcreates a need for supplementalcarbohydrates. The supplementprovides the carbohydratesneeded to fuel working musclesand to maintain blood glucoselevels and cognitive function.

Conclusions—Self-selectedwork rate is higher duringarduous wildland fire suppres-sion when carbohydrates aredelivered at a rate of 40 grams/hour (160 kilocalories/hour) ina 20-percent solutionadministered at the rate of 200milliliters/hour.

This study was supported byMTDC.

B. Ruby, S. Gaskill, D. Lankford, D.Slivka, D. Heil, and B. Sharkey. 2003.Carbohydrate Feedings IncreaseSelf-Selected Work Rates DuringArduous Wildfire Suppression. Paperaccepted for presentation at theJune 2003 meeting of the AmericanCollege of Sports Medicine, SanFrancisco.

SupplementalCarbohydrates

The effectiveness of consumingcarbohydrates duringendurance exercise has beenwidely documented. However,carbohydrate ingestion duringextended exercise at lowerintensities has received littleattention. This study attemptedto determine the effects ofcarbohydrate feeding on bloodglucose and self-selected hikingspeed during a prolonged

Figure 3—Blood glucose levels during a 24-kilometer hike.

submaximal exercise. Subjects(n = 12) completed two 24-kilometer hikes 7 days apart ina single-blind double-crossoverdesign. Blood glucoseconcentration was measuredwith an automated glucometerbefore the hike, hourly duringthe hike, and after the hike.Subjects consumed 200milliliters of a carbohydrate (40grams/hour, 20-percentmaltodextrin) or placebo drinkhourly. The subjects’ ratings ofperceived exertion wererecorded hourly using the Borg6–20 scale. Data were analyzedusing a priori plannedcomparisons across trials.

Blood glucose (millimoles) wassimilar for both groups beforeexercise and for the first 8kilometers of the hike.Afterward, blood glucoseremained significantly higher (p< 0.05) during the carbohydratetrial (figure 3).

Subjects self-selected a fasterhiking speed during thecarbohydrate trial,demonstrated by a significantdifference in return time (124and 136 minutes for thecarbohydrate and placebotrials, respectively, p < 0.05)despite no differences in theratings of perceived exertion(11.92 vs. 11.75, p < 0.05).These data demonstrate thatsupplemental carbohydratefeedings can improve self-selected exercise performanceduring low- to moderate-exertion extended hiking,regardless of the subject’srating of perceived exertion.

B. Ruby, S. Gaskill, and others. 2003.Liquid Carbohydrate FeedingImproves Self-Selected ExercisePerformance During a 24 km Hike.Paper accepted for presentation atthe June 2003 meeting of theAmerican College of SportsMedicine, San Francisco.

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Carbohydrate andCognitive Function

The brain requires acontinuous supply of glucose tofunction adequately. Duringaerobic exercise, peripheralglucose requirements increase,and carbohydratesupplementation improvesperformance. This studyinvestigated the effects ofcarbohydrate supplementationon cognitive function. A double-blind, placebo-controlled,between-subjects design wasused. Young men (n = 143) wererandomly assigned to one ofthree groups: a 6-percent (byvolume) carbohydrate, 12-percent carbohydrate, orplacebo beverage. Each groupreceived six doses. All subjectsconsumed two meals.

During the 10-hour study, thesubjects performed physicallydemanding tasks, including a19.3-kilometer (12-mile) roadmarch and two 4.8-kilometer (3-mile) runs, interspersed withrest and other activities.Subjects responded as rapidlyas possible to auditory stimuli(20 per hour) from vigilancemonitors they wore on theirwrists. A self-report moodquestionnaire was used toassess cognitive function.Vigilance consistently improvedin a dose-related manner whensupplemental carbohydrateswere administered. Vigilancewas highest for those receiving12-percent carbohydrate dosesand lowest for those receivingthe placebo. Mood resultsagreed with the results from thevigilance monitors. Subjectswho received carbohydratesreported less confusion andgreater vigor than did thosewho received the placebo.

Supplemental carbohydratesenhance vigilance and improve

mood during sustainedexertion. This study also showsthat monitoring devices can beused to assess the effects ofnutritional factors on cognitionduring field activities.

H. Lieberman, C. Falco, and S. Slade.2002. Carbohydrate AdministrationDuring a Day of Sustained AerobicActivity Improves Vigilance, asAssessed by a Novel AmbulatoryMonitoring Device, and Mood.American Journal of ClinicalNutrition, 76:120–127.

Carbohydrate andProtein Supplement

Will a carbohydrate and proteinsupplement be more effective inreplenishing muscle glycogenafter exercise compared to asupplement containing asmuch carbohydrate, but noprotein? After 2.5 hours ofintense cycling to depletemuscle glycogen stores,subjects (n = 7) received, in arank order design, asupplement with 80 grams ofcarbohydrates, 28 grams ofprotein, and 6 grams of fat(CHO-Pro), 80 grams ofcarbohydrates and 6 grams offat (LCHO), or 108 grams ofcarbohydrates and 6 grams offat (HCHO) 10 minutes afterexercise and 2 hours afterexercise. Muscle glycogen ofthe vastus lateralis muscle onthe front of the thigh wasdetermined using nuclearmagnetic resonancespectroscopy before exerciseand during 4 hours of recovery.Exercise significantly reducedthe muscle glycogen stores (40to 41 millimoles/liter). After 240minutes of recovery, muscleglycogen levels weresignificantly higher for theCHO-Pro treatment (88.8

millimoles/liter, compared to 70and 75.5 millimoles/liter for theLCHO and HCHO treatments,respectively). Glycogen storagedid not differ significantlybetween the LCHO and HCHOtreatments. These resultssuggest that a carbohydrate-protein supplement is moreeffective for rapidlyreplenishing muscle glycogenafter exercise than asupplement with as muchcarbohydrate, but no protein.

J. Ivy and others. 2002. Early Post-Exercise Muscle Glycogen Recoveryis Enhanced with a Carbohydrate-Protein Supplement. Journal ofApplied Physiology, 93:1337–1344.

Sleep and EnergyDeprivation

Studies examining the effects ofprolonged physiological stresshave relied primarily on teststhat were not occupationallyrelevant and often did notestablish test-retest reliability.This study evaluated changesin occupational taskperformance and bodycomposition during 72 hours ofmilitary occupational stress.Ten male subjects (22 years old,183 centimeters tall, weighing87 kilograms) participated inphysical performance testsduring days 1 to 4 of a controland experimental period.During the period, subjectsengaged in sustained physicalexertion of 4,500 kilocaloriesper day while sleeping for only2 hours per day and receivingonly 1,600 kilocalories per dayof nutrients. Militaryoccupational physicalperformance was measured by:

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• Time to complete a six-station indoor obstaclecourse

• Number of 20.5-kilogramboxes lifted to 1.3 metersduring a 10-minute box-lifting trial

• Landing distance from atarget for a 35-millimetergrenade throw

Subjects were provided withstrong verbal encouragement.Body mass (–3.1 percent), fat-free mass (–2.3 percent), and fatmass (–7.3 percent) all declinedsignificantly by the end of the4-day experimental period. Theobstacle course and box-liftingtrials showed temporal changesas performance wassignificantly lower on day 3 ascompared to day 1, but showedsome recovery on day 4. Thegrenade throw showed nochange during the period. Thedata show that soldiers are ableto perform militarily relevantphysical performance tasks at asimilar capacity to theirnormally rested and fed state,despite having lost fat-freemass, after 72 hours of militaryoperational stress (physicalexertion, sleep deprivation andrestricted caloric intake).

C. Pandorf and others. 2002.Physical Performance Responses to72 Hours of Prolonged Work, SleepDeprivation and Caloric Restriction.Medicine and Science in Sports andExercise, 34: s194. U.S. ArmyInstitute of Environmental Medicine.

Editors note: This study confirmsthe ability of trained and motivatedworkers to sustain performance ofmeaningful physical work despitefatigue caused by prolonged workand deprivation of food and sleep.

RiskManagement

Psychological/Physical cognitive

Exhaustion

Headaches

Rapid pulse

DrowsinessDizzinessLoss of coordination

Blurred vision

Vertigo

Table 3—Symptoms of hypoglycemia.

Anxiety

Depression

Irritability

Lack of concentration

ConfusionIndecisiveness

Hypoglycemia andCognitive Function

Low levels of blood sugar(hypoglycemia) can affectperformance, cognitivefunction, and behavior. Thebrain and nervous systemdepend on blood sugar (glucose)for energy. After a meal, glucoseis stored in the liver andmuscles. During prolongedexertion, the body uses glucoseas a source of energy. Storedglucose is depleted, bloodglucose declines, and thenervous system and cognitivefunction are adversely affected(table 3). During periods ofprolonged arduous work, it is

important to maintain adequateblood glucose levels to sustaincoordination, concentration,vigilance, and the ability tomake decisions.

Because blood sugar is used bymuscles during hard work,prolonged exertion cancontribute to hypoglycemia.Blood glucose levels can bemaintained with the use of solidand liquid carbohydratesupplements.

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Field NotesCarbohydrate andelectrolyte beveragesor sports drinks helpmaintain performance,cognitive ability, andimmune functionwhile they addressfluid replacementrequirements. Theelectrolytes replacesweat losses andminimize urinary fluidloss. Electrolytes mayalso reduce muscles’tendency to crampduring hours of workin the heat. Sportsdrinks are

Sports Beverages

Carbohydrate and electrolytebeverages or sports drinks helpmaintain performance,cognitive ability, and immunefunction while they addressfluid replacementrequirements. The electrolytesreplace sweat loss andminimize urinary fluid loss.Electrolytes may also reducemuscles’ tendency to crampduring hours of work in theheat. Sports drinks arerecommended for fluidreplacement during work andfor recovery after the shift.

During Work—Fluidreplacement during workrequires a balance betweenrestoring critical fluids and theneed for energy. Most sportsdrinks contain between 5 and 8percent of carbohydrates perliter of fluid. Higher levels ofcarbohydrates may seem toosweet or syrupy for use duringwork. High levels ofcarbohydrates can slowabsorption of the fluid. All themajor brands of sports drinksinclude moderate levels ofsodium and potassium, and afew contain small amounts ofmagnesium. A powdered drinkmix allows each firefighter tomix the drink to personal taste.Up to half of an individual’sfluid needs should be replacedwith a sports drink, and thebalance should be water.

Firefighters should takefrequent drinks to ensureconsumption of 1 liter of fluidper hour of work.

After Work—Rehydration orrecovery drinks may containmore carbohydrates and someprotein (1 gram of protein per 4grams of carbohydrates). Thecarbohydrates restore muscleand liver glycogen levels andthe protein aids musclerecovery. Electrolytes in thebeverage minimize urinarywater loss. A firefighter shouldconsume about 2 liters of thebeverage in the 2 hoursimmediately after work. Solidfood containing carbohydrates,protein, and some electrolyteswill also aid muscle recovery.Water also aids rehydration, butunless the water containselectrolytes, about one-third ofthe water will be lost in theurine.

High-Fat Diet?

Is prolonged work or endurancetraining possible on a high-fatdiet? In an experiment reportedin 1928, researchers studiedthe effects of 11 days ofexercise performance on a high-fat diet as compared to a high-carbohydrate diet. The authorsdescribed the subject’s abilityto handle the exercise:

“After the first two to threedays the subject felt very tiredand sleepy, in fact did sleepseveral hours betweenexperiments, and had no desireto work or to do anything else.The work seemed harder,although it was the same as inthe previous series. In the lastfew experiments the subjectbecame dizzy on the ergometer(bicycle) toward the end of thework period and afterwardexpressed the fear that hemight have fallen off. But hestuck pluckily until the serieswas completed. The very lastexperiment had to bediscontinued at the end of 6.4minutes because of dizziness.”

In contrast, when the subjectconsumed the carbohydratediet, all exercise tests wereperformed without problems.

An earlier study (1920) foundthat some subjects experiencedexcessive fatigue duringexertion after 3 days on a veryhigh-fat diet, while a few failedto observe an appreciabledifference. Current studies onthe topic are equally equivocal,suggesting the possibility of anindividual response to a high-fat diet. However, since high-fatintake suppresses the immuneresponse and has serioushealth consequences (heartdisease, obesity, diabetes), a

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All wildland firefighterhealth and safety reports areavailable on the Internet atthe address: http://www.fs.fed.us/cgi-bin/enter.pl?link=/pubs/htmlpubs/wfhsr/

Previous issues of WildlandFirefighter Health and SafetyReport include:

No. 1 Oxidative Stress Spring 2000

No. 2 Immune Function Fall 2000

No. 3 Heat Stress and Hydration Spring 2001

No. 4 Work Capacity Tests Fall 2001

No. 5 Work and Fatigue Spring 2002

If you have comments,questions, or suggestionsabout this project, send

them to Brian Sharkey at:bsharkey@fs.fed.us.

A firefighter collectsan immune functionmeasure (salivaryimmunoglobulin)and completes afatigue and moodquestionnaire aspart of the carbo-hydrate supplementstudy (Ruby andothers, p. 6). Theimmune functionand fatigue data willappear in the Spring2003 edition of thisreport.

Coming up. . .

The Spring 2003 WildlandFirefighter Health and SafetyReport will consider:

• Medical standards

• Medical examinations

• Medical tests

firefighter has no reason toconsume a high-fat diet.

Krogh and Lindhard. 1920. Bio-chemical Journal, 14: 290–363.Marsh and Murlin. 1928. Journal ofNutrition, 1: 105–137.

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Library Card

Sharkey, Brian. 2002. Wildland firefighter health and safety report No. 6. Tech. Rep.0251–2837–MTDC. Missoula, MT: U.S. Department of Agriculture, Forest Service,Missoula Technology and Development Center. 12 p.

This issue focuses on energy and nutrition and their influence on health andperformance. The report summarizes studies indicating that:

• Carbohydrate supplements taken hourly during long shifts of firefighting or 24-kilometer hikes, help maintain blood glucose levels and increase the workaccomplished.

• A 12-percent carbohydrate beverage helped subjects stay mentally vigilant during a19.3-kilometer road march and two 4.8-kilometer runs, interspersed with rest andother activities.

• A carbohydrate and protein supplement restored muscle glycogen more effectivelythan carbohydrates alone after exercise.

• Soldiers who received only 2 hours of sleep a day and only 1,600 kilocalories ofnutrients while undergoing 4,500 kilocalories of exertion a day for 4 days were ableto perform physically at near-normal levels, even though they lost 3.1 percent of bodymass during the period.

Keywords: carbohydrate, fire fighting, firefighting, hydration, nutrition, protein, rest,safety at work, working hours

Additional single copies of this document may be orderedfrom:

USDA Forest ServiceMissoula Technology and Development Center5785 Hwy. 10 WestMissoula, MT 59808-9361Phone: 406–329–3978Fax: 406–329–3719E-mail: wo_mtdc_pubs@fs.fed.us

For additional technical information, contact Brian Sharkeyat MTDC.

Phone: 406–329–3989Fax: 406–329–3719E-mail: bsharkey@fs.fed.us

Electronic copies of MTDC’s documents are available on theInternet at:

http://www.fs.fed.us/cgi-bin/enter.pl?link=pubs/

The Forest Service, United States Department of Agriculture (USDA), has developed this information for the guidance of its employees, its contractors, and its cooperating Federal and Stateagencies, and is not responsible for the interpretation or use of this information by anyone except its own employees. The use of trade, firm, or corporation names in this document is for theinformation and convenience of the reader, and does not constitute an endorsement by the Department of any product or service to the exclusion of others that may be suitable.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexualorientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille,large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 1400 Independence Avenue, SW, Washington, D.C. 20250–9410, or call (202)720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.