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Fluid and Electrolyte Replacement in Athletes

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Presentation on theme: "Fluid and Electrolyte Replacement in Athletes"— Presentation transcript:

1 Fluid and Electrolyte Replacement in Athletes
Dr. David L. Gee FCSN/PE 446 Required readings: Williams: Chapter 9 (focus on p ) ADA/ACSM Sports Nutrition Position Paper

2 Korey Stringer Minnesota Vikings Offensive Tackle


4 Water Balance: Normal

5 Water Output: Normal vs.Exercise

6 Water Intake: Normal vs Exercise

7 In 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 status

8 Heat and Sweat Production During Exercise
70kg subject, running 1 hr 900 Cal expended mechanical efficiency = 20% 180 Cal movement, 720 Cal heat

9 Heat and Sweat Production During Exercise
body specific heat = 0.83Cal/kg/deg 780 Cal -> 12.4 deg C = 22 deg F death

10 Heat 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 loss

11 Effect 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, death

12 Strategies for Avoiding Dehydration
NATA Position Statement: Fluid Replacement for Athletes J. Athletic Training 35: (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.

13 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 textbook

14 Strategies 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 gravity

15 Strategies for Avoiding Dehydration
Emphasize 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 min Individualize is far better

16 Strategies 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 electrolytes

17 Strategies for Avoiding Dehydration
Anticipate high risk conditions High temperature Uniform/clothing effects High humidity Indoor sports Low air movement Bright sun Dark colored clothing

18 Strategies for Avoiding Dehydration
Hyperhydration 1 pint, minutes prior to exercise Limited benefits Post-exercise rehydration Ideally completed within 2 hrs 1 pound wt loss = pts fluid replacement ACSM/ADA rec: oz per pound weight loss 1-1.5 pts per pound weight loss Replace CHO and electrolytes at same time to speed rehydration

19 Calculating hydration needs
Hydration Worksheet Available on course web page

20 Example: 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 = = 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 = 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) oz every 15 min

21 Practice 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?

22 Practice Problem Solution
Weight loss = = 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/15min

23 Electrolyte 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 hypernatremia Williams: “Thus, electrolyte replacement during exercise is not necessary.”

24 Electrolyte Strategies for Athletes
Most athletes do NOT need additional electrolytes Exception is for very high sweat losses (> 1hr or heat stress conditions) Replacement with excessive amounts of pure water can lead to hyponatremia (water intoxication) Dizziness, fainting, seizures, death Swelling of the brain Or asymptomatic Symptoms mimic dehydration Lack of ability to spit, dry skin, high body temperature indicates dehydration

25 Prevalence of Hyponatremia in Elite Athletes
1999 New Zealand Ironman Ultradistance 18% of finishers were hyponatremic 45% female finishers hyponatremic 14% male finishers hyponatremic Adequate water intake but inadequate electrolyte replacement 2002 Boston Marathon 13% with hyponatremia 0.6% with critical hyponatremia (3 runners)

26 Hyponatremia Common Causes Risk Factors excessive fluid consumption
excessive sodium loss in sweat excessive sweating “salty sweaters” Risk Factors heat stress environment long duration slower athletes non-acclimatized athletes small body weight (females)

27 Hyponatremia: Key Points
Hyponatremia unusual compared to prevalence of dehydration Know risk factors/situations Watch out for ‘too much of a good thing’ fluid intake should not exceed losses Sodium content of sport drinks are useful in preventing hyponatremia Sodium concentration in sports drink is more dilute than in sweat Palatability issues

28 Electrolyte replacement after exercise
Electrolyte imbalances can occur with: Low salt intake Repeated days of hard training 4 liters of sweat contains 3-7g sodium Additional losses in urine, stools Average US intake 6-9g sodium Increase sodium consumption salty foods Salt (2g Na/tsp) Salt tablets (during acclimatization, 1-2 wks)

29 Sport Drinks Water, CHO, electrolytes replacement during exercise
Provide water Provide dilute carbohydrates should be < 10% (<8% optimal) Gatorade: 6% Powerade: 8% Fruit juice: 11-15% Soft drinks: 11%

30 Carbohydrates in Sport Drinks
Glucose rapidly absorbed and utilized by muscle Fructose more slowly absorbed and utilized by liver to replace liver glycogen Sucrose (G-F) Glucose Polymers lower osmolarity than simple sugars and may allow for more rapid water absorption

31 Sport Drinks Provide electrolytes during exercise
replace Na and Cl lost in sweat enhances water uptake [NaCl] < 1000mg/L Gatorade: Na,Cl,K,P (460mg/L) Powerade: (Na,Cl) (300mg/L) Orange Juice: (10 mg Na/L) Soft drinks: (40 mg Na/L)

32 Sport Drinks Preferred tastes Particularly useful for:
Especially kids/teens Particularly useful for: endurance athletes high heat stress environments heavy sweaters

33 Specialty Sports Drinks
Gatorade Endurance Formula Nearly double sodium content + other electrolytes May be beneficial for athletes at risk for hyponatremia Gatorade Propel Dilute (3g CHO), “vitamin enhanced”, electrolytes ? Flavored drinks may be more readily consumed

34 Homemade Sport Drink Nancy Clark’s Sport Nutrition Guidebook, 2nd ed.
Yield: 1 quart 4 Tbl sugar 1/4 tsp salt 1/4 c boiling water 1/4 c orange juice (not concentrate) or 2 Tbl lemon juice 3 3/4 c cold water dissolve sugar,salt in hot water, add juice & cold water, chill 50Cal, 12gCHO, 110mgNa, 30mgK per cup

35 Homemade Sport Drink Hilary Warner, Nutrition Works!
2/3rd cup lemonade mix 2.25 quarts water ¼ - ½ tsp salt 8oz contains 65 Cal 15g CHO (6%) mg Na

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