Fluid and Electrolyte Replacement in Athletes

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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 Position Paper

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Korey Stringer 1974-2001 Minnesota
Vikings Offensive Tackle
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(No Transcript)
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Water Balance Normal
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Water OutputNormal vs.Exercise
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Water Intake Normal vs Exercise
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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

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Heat and Sweat Production During Exercise

• 70kg subject, running 1 hr
• 900 Cal expended
• mechanical efficiency 20
• 180 Cal movement, 720 Cal heat

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Heat and Sweat Production During Exercise

• body specific heat 0.83Cal/kg/deg
• 780 Cal -gt 12.4 deg C 22 deg F
• death

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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

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Effect of Dehydration on Physiological Function

• 2-4 wt loss - reduced muscular endurance time
• 4-6 wt loss - reduced muscular strength
  endurance, heat cramps
• gt 6 wt loss - severe heat cramps, heat
  exhaustion, heat stroke, coma, death

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Strategies for Avoiding Dehydration

• NATA Position Statement Fluid Replacement for
  Athletes
• J. Athletic Training 35212-224 (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.

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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

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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 lt 2 wt loss)
• Urine color or urine specific gravity

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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 10-15 min
• Individualize is far better

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Strategies for Avoiding Dehydration

• Understand each athletes sport dynamics
• Rest breaks/time outs
• Fluid accessibility
• Establish athletes acclimatized state
• Non-Acclimatized athletes
• sweat more
• lose more electrolytes

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Strategies 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 clothing

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Strategies 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 rehydration

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Calculating hydration needs

• Hydration Worksheet
• Available on course web page

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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 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 min

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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?

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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/15min

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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.

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Electrolyte Strategies for Athletes

• Most athletes do NOT need additional electrolytes
• Exception is for very high sweat losses (gt 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

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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)

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Hyponatremia

• Common Causes
• 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)

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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

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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)

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Sport DrinksWater, CHO, electrolytes replacement
during exercise

• Provide water
• Provide dilute carbohydrates
• should be lt 10 (lt8 optimal)
• Gatorade GS _at_ 6
• Powerade FGP _at_ 8
• Fruit juice FS _at_ 11-15
• Soft drinks F _at_ 11

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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

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Sport Drinks

• Provide electrolytes during exercise
• replace Na and Cl lost in sweat
• enhances water uptake
• NaCl lt 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)

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Sport Drinks

• Preferred tastes
• Especially kids/teens
• Particularly useful for
• endurance athletes
• high heat stress environments
• heavy sweaters

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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

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Homemade Sport DrinkNancy Clarks 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

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Homemade Sport DrinkHilary Warner, Nutrition
Works!

• 2/3rd cup lemonade mix
• 2.25 quarts water
• ¼ - ½ tsp salt
• 8oz contains
• 65 Cal
• 15g CHO (6)
• 65-130 mg Na