Fluid and electrolytes Flashcards
How much of our mass is water?
50-60%
What is daily water balance?
The balance of water performed by the kidney and hypothalamus by monitoring plasma osmolarity
What does a decrease in plasma osmolarity lead to?
The release of water (urine)
What does and increase in plasma osmolarity lead to?
retention of water and thirst
What are the different percentages of heat loss at rest?
60% radiation
12% convection
3% conduction
25% evaporation
How does the percentage of heat loss change during exercise?
up to 80% is lost via evaporation
What does 1L of sweat equal in heat loss?
2400kJ of heat
Where does the water for sweat come from?
Plasma, extracellular and intracellular
How much dehydration can start to effect performance?
2% of body weight
Why does dehydration lead to decreased performance?
Reduced blood volume Decreased max cardiac output Decreased plasma volume (thicker blood) Decreased skin blood flow Decreased sweat rate Decreased heat dissipation Increased core temp Increased use of muscle glycogen
What are some ways to measure dehydration?
% of body weight loss
Urine colour
Urine osmolarity
Is sweat hypotonic or hypertonic to plasma?
Hypotonic
how can electrolytes be replaced?
Sports drinks
What can too much water result in?
hyponatraemia -
lack of salt
where plasma sodium is <130mmol/L
How do you best replace lost fluid?
ingest initial bolus of ~500ml 1-2 hours before exercise
Regular intake of approximately ~150ml every 15-20min
After exercise consume 150% of water lost (not caffeine or alcohol)
