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Fluid and Electrolyte Replacement in Athletes Dr. David L. Gee FCSN/PE 446 Required readings: Williams: Chapter 9 (focus on p340-356) ADA/ACSM Sports Nutrition.

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Presentation on theme: "Fluid and Electrolyte Replacement in Athletes Dr. David L. Gee FCSN/PE 446 Required readings: Williams: Chapter 9 (focus on p340-356) ADA/ACSM Sports Nutrition."— 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: n Athletes greatly increase their water loss n Large increases in sweat loss n Some decreases in urine loss n Athletes need to greatly increase water intake n Large increases in fluid consumption n Smaller increases in food water and metabolic water n Athletes often fail to consume adequate amounts of fluids to maintain optimal hydration status

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

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

10 Heat and Sweat Production During Exercise n Evaporate 1 liter sweat = n 580 Cal heat n 720 Cal heat = evaporates 1.24 liters of sweat n Real conditions, approx. 2 liters or 4.4 pounds of water loss

11 Effect of Dehydration on Physiological Function n 2-4% wt loss - reduced muscular endurance time n 4-6% wt loss - reduced muscular strength & endurance, heat cramps n > 6% wt loss - severe heat cramps, heat exhaustion, heat stroke, coma, death

12 Strategies for Avoiding Dehydration n NATA Position Statement: Fluid Replacement for Athletes n J. Athletic Training 35: (2000) n Athletes do not voluntarily drink sufficient water to prevent dehydation during physical activity. n Thirst is a delayed response to dehydration. Thirsty athletes are already dehydrated.

13 Sports Nutrition Exam – Friday, May 5 n Format n multiple choice/true false n Short essay (2 – 2.5 pages) n Hypothetical case study n calculate exchange diet n Calculate fluid replacement needs n During exercise, after exercise (rehydration) n Bring calculator and pencils (no cell phone calculators) n Required readings n ADA/ACSM Position Paper: Sports Nutrition n Williams textbook

14 Strategies for Avoiding Dehydration n Establish a hydration protocol for athletes n Determine individual sweat rate n Changes in body weight (pre-post weighings) n 1 pound = 1 pint additional fluids during exercise n May also account for urine volume n Goal: no weight loss (or < 2% wt loss) n Urine color or urine specific gravity

15 Strategies for Avoiding Dehydration Emphasize continual fluid replacement n Replace fluids as they are lost n Practice fluid replacement n Gradually increase fluids n Body adapts to increase fluid consumption n Generally, cold fluids more rapidly absorbed n Use individual clear bottles for visual monitoring n Old Rule of Thumb: n cup per min n Individualize is far better

16 Strategies for Avoiding Dehydration n Understand each athletes sport dynamics n Rest breaks/time outs n Fluid accessibility n Establish athletes acclimatized state n Non-Acclimatized athletes n sweat more n lose more electrolytes

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

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

19 Calculating hydration needs n Hydration Worksheet n Available on course web page

20 Example: n Joe played tennis for two hours. He drank a 16oz bottle of water during his workout. n Initial weight = 180 lbs n Post-exercise weight = 176 lbs n Water loss = = 4 lbs n % body weight loss = 4/180 = 2.2% (dehydrated) n Total sweat loss = 4 pts + 1pt = 5 pts = 80 oz n To stay hydrated within 2% (minimum fluid replacement rate) n 2% x 180 = 3.6 lbs allowed wt loss = 3.6 pts allowable sweat loss n 5 pts – 3.6 pts = 1.4 pts = 22.4 oz n 22.4 oz/120 min = 0.19 oz/min = 2.8 oz every 15 min n Maximum fluid replacement rate n 80 oz / 120 min = 0.67 oz/min = 10 oz every 15 min n Recommended fluid replacement (per 15 min) n oz every 15 min

21 Practice Hydration Problem n LeBron participates in a 90 minute basketball workout each day. n Pre-workout weight = 240 lbs n Drinks 8 oz during workout n Post-workout weight = 234 lbs n To avoid dehydration and overhydration, how much fluid should LeBron consume during his next workout?

22 Practice Problem Solution n Weight loss = = 6 lbs (pts) n % weight loss = 6/240 = 2.5% (dehydrated) n Total sweat loss = 6pts + 0.5pts = 6.5pts = 104 oz. n Allowable sweat loss = 2% x 240 = 4.8 lbs n Minimum fluid replacement = 6.5 – 4.8 = 1.7 pts = 27.2 oz n 27.2 oz/90min =.30oz/min x 15 = 4.5 oz/15min n Maximum fluid replacement = 104oz/90 = 1.15 oz/min x 15 = 17 oz/15min n Rec Intake ~ 4-16 oz/15min

23 Electrolyte Replacement n Sweat from extracellular fluids n Major electrolytes are Na and Cl n Potassium and calcium are minor components n Sweat is hypo-osmolar (hypotonic) compared to plasma n Dehydration (with no/limited fluid replacement) leads to hypernatremia n Williams: Thus, electrolyte replacement during exercise is not necessary.

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

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

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

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

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

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

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

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

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

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

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

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

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