L5.2 Temperature & Fluid regulation

Question 1

Most energies from metabolism is dissipated as heat, what are the methods of heat loss?

Answer 1

• Conduction (more rapid in water than air)
• Convection - heat loss from movement of air across body
• Radiation

Question 2

What happens to core temperature during exercise?

Answer 2

Core temperature rises (slightly) during exercise and plateaus

Question 3

What is the major heat loss mechanism?

Answer 3

• Sweating (major heat loss mechanism) → proportional to exercise intensity

Question 4

What is in sweat?

Answer 4

• Sweat is hypotonic (mainly water)
• But also contains Na+

Question 5

What happens to the sweating rate of trained athletes?

Answer 5

• Trained athletes → lower Na+ in sweat (from action of aldosterone)
  
  • Maintains higher plasma vol → ∴↑BV in trained athletes

Question 6

What happens during hyperthermia & hypovolemia during exercise?

Answer 6

• ↓BF to muscles (fatiguing it)
• ↓Q during exercise in heat (when pre-exposed to heat) due to vsaodilated skin
  
  • ↓power output

Question 7

What is the effect of pre-cooling?

Answer 7

• ↑endurance (but still has the same final core temp)

Question 8

What are the strategies to enhance performance in heat?

Answer 8

• Heat acclimatisation:
  
  • ↑BV, ↓HR, core/skin temp
  • ↑sweat & have earlier onset & more diluted sweat
  • ↓muscle glycogen use (∴muscle temp lower)
  • ↓plasma [A]
• Pre-cooling
• Fluid ingestion (blunts rise in core temp - only has small effect)
• Fluid replacement blunts CV drift (Maintain SV, ↑BV, ↓HR)
  
  • ↓core temp
  • ↓plasma [Na+]
  • ↓glycogen use from [A]
• ↑plasma renin & aldosterone → maintain salt balance