Fluid and Electrolytes During Exercise

What is dehydration and how does it affect the body?

Loss of bodily water

Can impair the body and physical performance
can lead to death

What is the function of the water?

Forms fluid of our blood
participates in metabolic reactions

Serves as solvent for protein, glucose, vitamins, minerals
forms fluid portions of sweat
carries heat from internal portions of body to the surface to maintain normal body temp
Major constituent of lubricants of joints
major constituent of spinal fluid, eye fluid
major constituent of amniotic fluid during pregnancy

What are the main sources of water intake?

Fluids and foods

What are the 4 primary ways the body loses water daily?

urine
sweat
feces
insensible respiration

How do you calculate sweat loss

(pre-weight + fluid intake)-(post-weight + fluid intake) x hrs exercised

What are electrolytes?

Mineral salts that dissolve in water and form ions

What is the main role of the electrolytes?

Allow electrical charges to occur and are essential for excitable tissues like muscles and neurons

What is osmotic pressure?

Force created to draw water through a membrane

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Why does water follow electrolytes?

Cells controls the movement of water indirectly by controlling movement of electrolytes in and out of the cell

How does the body conserve sodium when levels are low?

Kidneys reabsorb sodium from urine under hormonal influence (e.g., aldosterone)

What happens if there is an electrolyte imbalance?

lead to severe injury, dysfunction, and death

What happens to electrolytes in individuals who train more in hot environments?

They will sweat more but will be less concentrated due to the kidneys and GI tract conserving more electrolytes in the body

What controls the thirst mechanism?

The hypothalamus, in response to plasma osmolality

Why is thirst not a perfect indicator of hydration needs?

Thirst signals only after partial dehydration has already occurred

What happens when you’re dehydrated during exercise?

Increased metabolic rate= need to dissipate heat=sweat= water loss

What happens to aerobic performance with 2–3% dehydration?

Aerobic capabilities decline; reduced plasma volume leads to higher heart rate and cardiovascular strain

How does dehydration affect anaerobic performance?

Significant strength loss is rare below 5% dehydration, but power and high-intensity endurance (>30s) may decline

What are the two methods of hydration assessment?

Body weight and urine color

What are the laboratory methods of hydration assessment?

1. Urine specific gravity

2. Plasma osmolality