sports med2 set 2

Water in human body

main component of body mass and essential for survival

Normal hydration (women)

about 45%–60% body water

Normal hydration (men)

about 50%–65% body water

Intracellular fluid

fluid inside cells

Extracellular fluid

fluid outside cells

Intracellular fluid proportion

about 2/3 of total body water

Extracellular fluid proportion

about 1/3 of total body water

Intracellular sodium level

low Na+ concentration inside cells

Intracellular potassium level

high K+ concentration inside cells

Extracellular sodium level

high Na+ concentration outside cells

Extracellular potassium level

low K+ concentration outside cells

Plasma

liquid part of blood in vessels (extracellular fluid)

Interstitial fluid

fluid between cells (extracellular fluid)

Fat-free body tissue water content

about 75% water

Fat tissue water content

about 10% water

Higher body fat effect

lower total body water percentage

Blood composition

about 10% of body weight

Blood plasma composition

about 55% of blood and 90% water

Total blood volume

about 5 liters in average adult

Water functions in body

regulates temperature, transports nutrients, protects organs, lubricates joints

Water and kidneys

helps remove waste and supports kidney function

Dehydration

loss of more body water than intake

Exercise dehydration threshold

1–2% body weight loss affects performance

Clinical dehydration definition

2% or more body weight loss from water loss

Vomiting dehydration cause

fluid loss from digestive system

Diarrhea dehydration cause

rapid fluid loss from intestines

Fever dehydration cause

increased fluid loss through skin

Diuretics

substances that increase urine output

Excessive sweating

primary cause of exercise dehydration

Sweat origin

derived from extracellular fluid (interstitial fluid)

Sweat sodium concentration

about 10–90 mmol/L

Extracellular sodium concentration

about 140 mmol/L

Electrolytes

charged minerals including Na+, K+, Ca++, Cl-, Mg++

Electrolyte role

regulate nerve signals and muscle contraction

Osmotic pressure

force created by solute concentration differences across membranes

High osmotic pressure

occurs when solute concentration increases

Osmosis direction

water moves toward higher solute concentration

Hydration and electrolytes relationship

fluid balance depends on electrolyte concentration

Overhydration risk

dilution of electrolytes (hyponatremia)

Electrolyte loss risk

impaired nerve and muscle function

Sweat rate calculation

body weight before and after exercise minus fluid intake

Heat exhaustion risk

fluid and electrolyte imbalance during exercise

Heat stroke risk

severe failure of thermoregulation due to dehydration

Kidney function role

maintains fluid and electrolyte balance