This document discusses fluid balance and exercise. It notes that water makes up 65-90% of human cells and plays key roles like transporting nutrients and regulating temperature. Exercise increases water loss through sweating and respiration. Fluid loss of 4-5% can reduce work capacity by 20-30%. The hypothalamus regulates body temperature during exercise through sweating and blood flow. Dehydration during exercise decreases performance, so fluid intake is important before, during, and after exercise to replace water and electrolytes lost through sweat.

1. 9--Fluids and exercise
Nutrition and Fitness
Dr. Siham Gritly

2. Water
• Water is the most abundant chemical
compound in living human cells, accounting
for 65-90% of each cell.
Each water molecule consists of two hydrogen
atoms bonded to one oxygen atom, but the
mass of each oxygen atom is much higher than
the combined mass of the hydrogen.
Dr. Siham Gritly

3. Importance of water
Main functions of water;
1-water provide the medium for the
solubilization and passage of nutrients organic
and inorganic from blood to the cells
2-water transport nutrients and waste products to
and from cells through blood stream
Dr. Siham Gritly

4. 3-it serves as the medium where intracellular
metabolic reactions take place
4-regulate body temperature; water major
constituent of sweat and through evaporation
from the surface of the skin (conduction,
convection, radiation, evaporation)
5-control osmotic pressure in the body and
maintaining a proper balance between water and
electrolytes
Dr. Siham Gritly

5. Distribution of Water in the body
• The body water is the most abundant constituent
of human body
• It divided into two major compartments;
1-intracellular compartment includes all water
enclosed within cell membranes (28L)
2-extracellular compartment; external to cell
membranes, (14L)
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6. Extracellular water divided into; plasma and the
interstitial fluid.
The interstitial fluid provide the medium for the
passage of nutrients and metabolic products
back and forth between the blood and cells
Dr. Siham Gritly

7. Fluids and exercise
• exercise increases the loss of water in two
ways
• 1-it increase rate respiratory tract
• 2-exercise increase the body heat and thus
result in excessive sweating of respiration,
which increase water loss through the skin
Dr. Siham Gritly

8. • depletion of water occurs through sweating and
respiration
• -much of water lost through sweating comes from
the blood leading to reduce the blood volume that
may threaten cardiovascular function
• -when fluid losses; sweating and blood flow to the
skin are decrease and temperature elevated
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9. • -fluid loss of 4 to 5% reduce work capacity by 20 to
30% and thus impairs performance
• -the amount of fluid lost during exercise depends on the
intensity and duration; effort, temp and humidity
• fluid losses should be monitored with body weight
measurements and urine color
• -one pound body loss is equal to 2 cups of fluid that
should be replaced
Dr. Siham Gritly

10. • -dark yellow urine can indicate dehydration
• -during long and intense exercise athletes
should replace water at regular intervals
• -continuous replacement is important during
and after exercise
Dr. Siham Gritly

11. How exercise affect body temperature
• During exercise the metabolic rate production
increase (energy metabolism)
• Energy during exercise released as heat
• The total amount of heat produced depends on
the intensity and duration of exercise
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12. Regulation of body temperature during
exercises
• Hypothalamus in the brain responsible for many
physiological body function including body
temperature.
• Hypothalamus receive information or output from;-
• 1-skin by sending impulses to hypothalamus
• 2-blood temperature directly affect hypothalamus and
influences the thermostat
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13. Exercise;
• look for related glands that regulate body fluids
Dr. Siham Gritly

14. • regulatory center of hypothalamus regulated
body temperature during exercises through;
• 1-sweating begin and evaporation will remove
heat away from the body
• 2-blood will come closer to the skin so that
heat may get closer to the outside and radiate
away
Dr. Siham Gritly

15. Hypothermia and hyperthermia
• Hypothermia
• In cold , wet and windy environment
conditions heat is lost more rapidly than it is
produced through exercise
• Athletes can inter in a condition known as
hypothermia
• Early sign of Hypothermia or low body
temperature are;- muscular in coordination and
mental confusion
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16. • hyperthermia
• During exercising in warm or hot environment
and air movement and radiation can all
increase body temperature through the skin
• Hyperthermia lead to limiting physical
performance and have very dangerous effect of
the athletes (central neural fatigue,
cardiovascular strain, muscle metabolism and
dehydration)
Dr. Siham Gritly

17. How heat is lost
• Heat loss through four physical means;
1- conduction; heat is transferred from the body
by direct physical contact, such as when
individual sit on a cold seat
2- convection;-heat is transferred by movement
of air or water over the body
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18. 3- radiation;-heat energy radiates from the body
into surrounding air
4- evaporation;-heat is lost from the body when
it is used to convert sweat to a vapor, it is
known as the heat of vaporization.
Dr. Siham Gritly

19. Dehydration and exercises
• Dehydration; is the reduction of body water
below the normal level of hydration, this
means that water output exceeds water intake.
Dehydration lead to hypohydration
• Many expert suggested that dehydration lead
to decrease of intracellular and extracellular
fluids which have negative effect of athlete
performance.
Dr. Siham Gritly

20. The physiological effect of Dehydration during
exercises
• The main physiological effect of dehydration
during exercise are;-
• 1-decrease plasma volume
• 2-increase plasma osmolality (the ionic
concentration of the dissolved substance/ unit
of solvent) or the concentration within a
fluid
• 3-increase viscosity
• 4-decrease blood volume
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21. • 5-decrease stroke volume (amount of blood
pumped by the heart per beat)
• 6-increase heart rate
• 7-decrease cardiac output (is the amount of blood
pumped by the heart in 1 minute measured in
L/min)
• 8-decrease skin blood flow
• 9-decrease sweat rate
• 10-increase body temperature
Dr. Siham Gritly

22. The importance of hydration during
exercises
• Fluid losses in excess of 5% of body weight
can reduce exercise capacity by as much as
30%.
• Electrolytes such as sodium, and to a lesser
extent magnesium and potassium, are also lost
from the body with sweat..
• It is therefore important to keep well-hydrated
by drinking before, during and after exercise.
Dr. Siham Gritly

23. Diet strategies
• regular diet that meets energy and nutrient
needs will replenish lost electrolytes.
• exercising that lasting more than one hour,
sports drinks may be needed to replace fluids
and electrolytes.
• Salt tablets can and impair performance; they
increase potassium losses, irritate the stomach,
and cause vomiting.
Dr. Siham Gritly

24. Hydration and exercise
• Before exercise
• It is important to begin an exercise session well-hydrated.
Drinking 400 to 500ml of fluid 10 to 15 minutes prior to
exercise is recommended.
• During exercise
• it is suggested that 150 to 250ml of fluid should be drunk
every 15 minutes. The choice of drink depends on the
intensity and duration of the activity.
• After exercise
• After exercise, rehydration and full recovery can only be
achieved if the electrolytes which have been lost in sweat
are replaced as well as the water
Dr. Siham Gritly

25. Electrolyte balance and physical
activities
• Electrolytes are substances which in solution
conducts an electrical current
• The solution referred to an electrolyte solution
• Acids, base and salts are common electrolytes,
they usually dissociate (disconnect) into ions,
particles carrying either a positive (cation) or
negative (anion) electric charge such as nerve
impulse
Dr. Siham Gritly

26. Electrolyte Losses and Replacement
• When a person sweats, small amounts of
electrolytes—the electrically charged minerals
sodium, potassium, chloride, and
magnesium—are lost from the body along with
water.
• Losses are greatest in beginners;
• training improves electrolyte retention
Dr. Siham Gritly

27. • Intracellular fluids:
POTASSIUM,PHOSPHATE,PROTEINS
• Extracellular fluids; and PLASMA):
SODIUM,CHLORIDE,BICARBONATE
• Semester V1 in more details
Dr. Siham Gritly

28. References
• Sareen Gropper, Jack Smith and James Groff, Advanced Nutrition and
Human Metabolism, fifth ed. WADSWORTH
• Guyton, C. Arthur. 1985. Textbook of Medical Physiology. 6th edition,
W.B. Company
• Fluids and Electrolytes During Exercise. author: Stan Reents, PharmD.
Original Posting: 05/06/2007 10:37 AM
• Ellie Whitney and Sharon Rady Rolfes; Under standing Nutrition, Twelfth
Edition. 2011, 2008 Wadsworth, Cengage Learning
• Melvin H Williams 2010; Nutrition for Health, Fitness and Sport. 9th ed,
McGraw Hill
• Heymsfield, SB.; Baumgartner N.; Richard and Sheau-Fang P. 1999.
Modern Nutrition in Health and Disease; Shils E Maurice, Olson A.
James, Shike Moshe and Ross A. Catharine eds. 9th edition
Dr. Siham Gritly