1. MODULE 8 – FLUID AND
ELECTROLYTE BALANCE DURING
EXERCISE

2. Athletes need both!
2

3. Heat Removal
• Exercise increases core temperature.
For every L of O2 consumed during
exercise ~5 kcal is produced but only
1kcal is used for mechanical work – the
rest is heat
• Increases in core temperature:
– Increase blood flow to the skin
– Initiate sweating

4. Sweating and Fluid Loss
• Mild to moderate work and routine
physical training typically result in
whole-body sweat losses of about
~0.8-1.4 L/h.
• Evaporation of 1L of water from
the skin will remove 573 kcal of
heat from the body.
• Heat loss via evaporation of
sweat is largely dependent on the
humidity (proximate to the skin) in
which the athlete is working.
• Individual sweat rates and fluid
losses vary widely between
athletes and across sports.

6. Avoid “Hitting the Wall”

7. In cool laboratory conditions, VO2max has been shown to
decrease with fluid losses > 2% BW...
In the heat, sweat rates increase even more such that fluid intake
must be even more closely monitored.
100%
80%
Capacity
Exercise
60%
0 1 2 3 4 5
Body weight loss

8. Effects of dehydration on sports
performance.
% OF BODY WEIGHT PHYSIOLOGICAL EFFECT
LOST AS SWEAT
4% CAPACITY FOR MUSCULAR
DECREASES
5% HEAT EXHAUSTION
7% HALLUCINATIONS
10% CIRCULATORY COLLAPSE / HEAT
STROKES

9. How does sweating (fluid loss) work to decrease
performance?
increase in plasma osmolarity (higher
concentration of solute in solution)
release of vasopressin (ADH) from
the posterior pituitary gland.
ADH causes the kidney to re-absorb
water
Urine volume goes DOWN dramatically to
preserve blood osmolarity, volume and
pressure
As exercise progresses, the transfer of
body
water into the plasma cannot keep up
with

10. Daily Water Balance
Athletes need to be fully hydrated before training/competition
The average sedentary person excretes about
2700 milliliters of water/day (1400 from urine, 1100
sweat/breath)
To replace that 2700 ml, get:
• 300-400 ml from metabolism,
• 1000 ml from food and
• 1300-1400 ml from beverages
2700 ml

11. Athletes and Daily Water Balance

12. Water Balance: Normal
2500
2000 Metab
Food
1500 Fluids
Stool
1000 Breath
Sweat
Urine
500
0
Output Intake

13. Water Output:
Normal vs.Exercise
5000
4000
Stool
3000
Breath
Sweat
2000
Urine
1000
0
Normal Exercise

14. Water Intake:
Normal vs Exercise
5000
4000
3000 Metab
Food
2000 Fluids
1000
0
Normal Exercise

15. 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

16. Guidelines
1. Intake approximately 500ml. (2 cups) of a cool
beverage 2 hours before a workout, 250ml (1
cup) in final 15-30 minutes.
2. During activity, drink fluid frequently- for
example, 150 -200ml(1 cup) every 15-20
minutes.
3. After a workout, replenish fluids at a rate of
1litre for every kilogram of body weight lost.
Weight should be regained, before the next
workout, indicating rehydration.

17. • Hydrate properly before prolonged exercise in hot
environments.
• Water is the ideal fluid replacement, although flavored
beverages may be more effective at promoting drinking.
• The salt in the beverages or as food can promote
rehydration more effectively than plain water when
significant weight loss has occurred through sweating.
• Urine should be pale yellow or clear. This indicates that
you are in a hydrated status

18. Sports Drinks
TYPE CONTENT
ISOTONIC FLUID, ELECTROLYTES , 6-8%
CARBOHYDRATE
HYPOTONIC FLUID , ELECTROLYTES , LOW
CARBOHYDRATE
HYPERTONIC HIGH LEVEL OF
CARBOHYDRATE

19. The osmolality of a fluid is a measure of the number of particles in a
solution.
In a drink, these particles will comprise of carbohydrate, electrolytes,
sweeteners and preservatives.
In blood plasma the particles will comprise of sodium, proteins and
glucose.
Blood has an osmolality of 280 to 330mOsm/kg. Drinks with an
osmolality of 270 to 330mOsm/kg are said to be in balance with
the body's fluid and are called Isotonic.
Hypotonic fluids have fewer particles than blood and Hypertonic have
more particles than blood.
Consuming fluids with a low osmolality, e.g. water, results in a fall in
the blood plasma osmolality and reduces the drive to drink well
before sufficient fluid has been consumed to replace losses.

20. Isotonic - quickly replaces fluids lost by sweating and supplies a
boost of carbohydrate. This drink is the choice for most athletes -
middle and long distance running or team sports. Glucose is the
body's preferred source of energy therefore it may be appropriate
to consume Isotonic drinks where the carbohydrate source is
glucose in a concentration of 6% to 8% - e.g. High Five, SiS Go,
Boots Isotonic, Lucozade Sport.
Hypotonic - quickly replaces fluids lost by sweating. Suitable for
athletes who need fluid without the boost of carbohydrate e.g.
jockeys and gymnasts.
Hypertonic - used to supplement daily carbohydrate intake normally
after exercise to top up muscle glycogen stores. In ultra distance
events, high levels of energy are required and Hypertonic drinks
can be taken during exercise to meet the energy demands. If used
during exercise Hypertonic drinks need to be used in conjunction
with Isotonic drinks to replace fluids.

21. SALT
INSIDE CELL OUTSIDE CELL
DEHYDRATION
WATER

22. ELECTROLYTES
Electrolytes are electrically charged particles that
conduct electricity as they dissolve in liquids such as
water or blood.

23. SODIUM “ THE YOUTH ELEMENT”
• Keeps joints limber
• 60% is present in the fluid outside the cell;10% is present
inside the cell;30% is present in the bones.
• Excessive sweat causes sodium loss as in
 Hard manual labor
 Professional athletes
 Starvation
 Vomiting & diarrhoea

24. POTASSIUM “THE ALKALISER”
• Makes up 5% of the mineral content of the body.
• Plays a vital role in making muscle protein from
amino acids.
• Concentration of sodium and potassium are inversely
proportional to each other.
• Dehydration depletes potassium and increase muscle
breakdown

25. FUNCTIONS OF ELECTROLYTES
• Regulates water balance
• Interacts with the cell membranes to allow nutrients
to enter cells and waste to leave
• Maintains acid-base balance
• Conducts nerve impulse

26. BODY WATER
60% OF
BODY WEIGHT
20%
40%
EXTRA
INTRA
CELLULAR
CELLULAR

27. WATER BALANCE
Drinking H2O Food stuffs
Metabolic
& beverages 700 ml
water 300ml
1500 ml
Body water
Urine Feces
Skin Lungs
1500 ml 150 ml
450 ml 400 ml

28. INTERESTING FACTS ON WATER
• Water delivery inside the cells is more effective in the nights
when the body is horizontal
• When we drink enough water to pass clear urine, we also pass
out a lot of the salt that was held back
• Nothing kills life quicker than lack of water
• The salinity of the water outside the cells in our bodies is the
same as the ocean

29. 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

30. Strategies for Avoiding Dehydration
• Establish a hydration
protocol for athletes
• Determine individual sweat rate
– Changes in body weight (pre-
post weighings)
– 1 kg = 1043ml
additional fluids during
exercise
– May also account for
urine volume
– Goal: no weight loss
(or < 2% wt loss)
– Urine color or urine specific
gravity

31. 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

32. 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

33. 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

34. Strategies for Avoiding Dehydration
• Hyperhydration
– 500 ml, 15-30 minutes prior to exercise
– Limited benefits
• Post-exercise rehydration
– Ideally completed within 2 hrs
• ACSM/ADA rec: 700ml per 500gms body weight
lost
• Replace CHO and electrolytes at same time to speed
rehydration

35. Example:
• Joe played tennis for two hours( 120 mins). He drank
a 500ml bottle of water during his workout.
– Initial weight = 70
– Post-exercise weight = 68
• Water loss =70-68 = 2 kgs
• % body weight loss = 2/70 = 2.8% (dehydrated)
• Total sweat loss = approx 2 litres
• To stay hydrated within 2% (minimum fluid
replacement rate)
– 2% x 70 = 1.4 kgs allowed wt loss = 1.4 litres allowable sweat loss
• Maximum fluid replacement rate
– 1.4 lits/ 120 min = 11ml/min = 175 ml every 15 min
• Recommended fluid replacement (per 15 min)
– 2.5-10 oz every 15 min

36. Sport Drinks
Water, CHO, electrolytes replacement during exercise
• Provide water
• Provide dilute carbohydrates
– should be < 10% (<8% optimal)
– Gatorade: G+S @ 6%
– Powerade: F+GP @ 8%
– Fruit juice: F+S @ 11-15%
– Soft drinks: F @ 11%

37. 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

38. 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)

39. Homemade Sport Drink
• lemonade mix(nimbu pani powder)
• 1000ml water
• ¼ - ½ tsp salt
• 6 tablespoon Glucose
• 1 tablespoon Sucrose
• ½ tbsp baking powder