Fluid and Electrolyte Replacement in AthletesSlide 2Slide 3Water Balance: NormalWater Output: Normal vs.ExerciseWater Intake: Normal vs ExerciseIn comparison to non-athletes:Heat and Sweat Production During ExerciseSlide 9Slide 10Effect of Dehydration on Physiological FunctionStrategies for Avoiding DehydrationSports Nutrition Exam – Friday, May 5Slide 14Slide 15Slide 16Slide 17Slide 18Calculating hydration needsExample:Practice Hydration ProblemPractice Problem SolutionElectrolyte ReplacementElectrolyte Strategies for AthletesPrevalence of Hyponatremia in Elite AthletesHyponatremiaHyponatremia: Key PointsElectrolyte replacement after exerciseSport Drinks Water, CHO, electrolytes replacement during exerciseCarbohydrates in Sport DrinksSport DrinksSlide 32Specialty Sports DrinksHomemade Sport Drink Nancy Clark’s Sport Nutrition Guidebook, 2nd ed.Homemade Sport Drink Hilary Warner, Nutrition Works!Fluid and Electrolyte Replacement in AthletesDr. David L. GeeFCSN/PE 446Required readings:Williams: Chapter 9 (focus on p340-356)ADA/ACSM Sports Nutrition Position PaperKorey Stringer1974-2001Minnesota VikingsOffensive TackleWater Balance: Normal05001000150020002500Output IntakeMetabFoodFluidsStoolBreathSweatUrineWater Output:Normal vs.Exercise010002000300040005000Normal ExerciseStoolBreathSweatUrineWater Intake: Normal vs Exercise010002000300040005000Normal ExerciseMetabFoodFluidsIn comparison to non-athletes:Athletes greatly increase their water lossLarge increases in sweat lossSome decreases in urine lossAthletes need to greatly increase water intakeLarge increases in fluid consumptionSmaller increases in food water and metabolic waterAthletes often fail to consume adequate amounts of fluids to maintain optimal hydration statusHeat and Sweat Production During Exercise70kg subject, running 1 hr900 Cal expendedmechanical efficiency = 20%180 Cal movement, 720 Cal heatHeat and Sweat Production During Exercisebody specific heat = 0.83Cal/kg/deg780 Cal -> 12.4 deg C = 22 deg FdeathHeat and Sweat Production During ExerciseEvaporate 1 liter sweat = 580 Cal heat720 Cal heat = evaporates 1.24 liters of sweatReal conditions, approx. 2 liters or 4.4 pounds of water lossEffect of Dehydration on Physiological Function2-4% wt loss - reduced muscular endurance time4-6% wt loss - reduced muscular strength & endurance, heat cramps> 6% wt loss - severe heat cramps, heat exhaustion, heat stroke, coma, deathStrategies for Avoiding DehydrationNATA Position Statement: Fluid Replacement for AthletesJ. Athletic Training 35:212-224 (2000)“Athletes do not voluntarily drink sufficient water to prevent dehydation during physical activity.”Thirst is a delayed response to dehydration. Thirsty athletes are already dehydrated.Sports Nutrition Exam – Friday, May 5Formatmultiple choice/true falseShort essay (2 – 2.5 pages)Hypothetical case studycalculate exchange dietCalculate fluid replacement needsDuring exercise, after exercise (rehydration)Bring calculator and pencils (no cell phone calculators)Required readingsADA/ACSM Position Paper: Sports Nutrition Williams textbookStrategies for Avoiding DehydrationEstablish a hydration protocol for athletesDetermine individual sweat rateChanges in body weight (pre-post weighings)1 pound = 1 pint additional fluids during exerciseMay also account for urine volumeGoal: no weight loss (or < 2% wt loss)Urine color or urine specific gravityStrategies for Avoiding DehydrationEmphasize continual fluid replacementReplace fluids as they are lostPractice fluid replacementGradually increase fluidsBody adapts to increase fluid consumptionGenerally, cold fluids more rapidly absorbedUse individual clear bottles for visual monitoringOld Rule of Thumb:0.5-1 cup per 10-15 minIndividualize is far betterStrategies for Avoiding DehydrationUnderstand each athlete’s sport dynamicsRest breaks/time outsFluid accessibilityEstablish athlete’s acclimatized stateNon-Acclimatized athletes sweat morelose more electrolytesStrategies for Avoiding DehydrationAnticipate high risk conditionsHigh temperatureUniform/clothing effectsHigh humidityIndoor sportsUniform/clothing effectsLow air movementUniform/clothing effectsBright sunDark colored clothingStrategies for Avoiding DehydrationHyperhydration1 pint, 15-30 minutes prior to exerciseLimited benefitsPost-exercise rehydrationIdeally completed within 2 hrs1 pound wt loss = 1.5-2 pts fluid replacementACSM/ADA rec: 16-24 oz per pound weight loss1-1.5 pts per pound weight lossReplace CHO and electrolytes at same time to speed rehydrationCalculating hydration needsHydration WorksheetAvailable on course web pageExample:Joe played tennis for two hours. He drank a 16oz bottle of water during his workout.Initial weight = 180 lbsPost-exercise weight = 176 lbsWater loss = 180-176 = 4 lbs% body weight loss = 4/180 = 2.2% (dehydrated)Total sweat loss = 4 pts + 1pt = 5 pts = 80 ozTo stay hydrated within 2% (minimum fluid replacement rate)2% x 180 = 3.6 lbs allowed wt loss = 3.6 pts allowable sweat loss5 pts – 3.6 pts = 1.4 pts = 22.4 oz22.4 oz/120 min = 0.19 oz/min = 2.8 oz every 15 minMaximum fluid replacement rate80 oz / 120 min = 0.67 oz/min = 10 oz every 15 minRecommended fluid replacement (per 15 min)2.5-10 oz every 15 minPractice Hydration ProblemLeBron participates in a 90 minute basketball workout each day.Pre-workout weight = 240 lbsDrinks 8 oz during workoutPost-workout weight = 234 lbsTo avoid dehydration and overhydration, how much fluid should LeBron consume during his next workout?Practice Problem SolutionWeight loss = 240-234 = 6 lbs (pts)% weight loss = 6/240 = 2.5% (dehydrated)Total sweat loss = 6pts + 0.5pts = 6.5pts = 104 oz.Allowable sweat loss = 2% x 240 = 4.8 lbsMinimum fluid replacement = 6.5 – 4.8 = 1.7 pts = 27.2 oz27.2 oz/90min = .30oz/min x 15 = 4.5 oz/15minMaximum fluid replacement = 104oz/90 = 1.15 oz/min x 15 = 17 oz/15minRec Intake ~ 4-16 oz/15minElectrolyte ReplacementSweat from extracellular fluidsMajor electrolytes are Na and ClPotassium and calcium are minor componentsSweat is hypo-osmolar (hypotonic) compared to plasmaDehydration (with no/limited fluid replacement) leads to