9--Fluids and exercise

Nutrition and Fitness

Dr. Siham Gritly

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

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

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

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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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

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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

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• 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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• -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

Dr. Siham Gritly

• -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

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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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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Exercise;

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• look for related glands that regulate body fluids

• 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

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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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• 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)

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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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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.

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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.

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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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• 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

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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.

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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

Dr. Siham Gritly

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

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

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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

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• Intracellular fluids:POTASSIUM,PHOSPHATE,PROTEINS

• Extracellular fluids; and PLASMA):SODIUM,CHLORIDE,BICARBONATE

• Semester V1 in more details

Dr. Siham Gritly

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. 9 th 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