Lecture 14 Flashcards
Why is heat dissipation necessary?
Heat dissipation is to avoid critical hyperthermia
What are the 4 mechanisms of heat loss during exercise?
conduction
Convection
radiation
evaporation
What is the problem with humid conditions?
High humidity conditions prevent evaporation due to water vapour pressure gradient.
What happens to core temperature during exercise?
Core temperature increases during exercise and levels off eventually. Heat loss mechanisms take time to kick in
What 3 mechanisms correlate with exercise intensity?
Sweating
Heat production
VO2 max
Is sweat hypo or hyper tonic to plasma?
Sweat is hypotonic to blood plasma
Can sweat glands reabsorb sodium?
Yes
Why do trained individuals have less sodium in their sweat?
Trained individuals have less sodium in sweat due to increased sodium reabsorption as a response to aldosterone,
What happens to cardiac output during exercise and why does this happen?
Cardiac output increases at rest in hot weather with a big percentage caused by increased skin circulation.
High core temperature increases directing of blood flow to the skin which directs blood flow away from muscles.
What happens to glycogen utilization during exercise in hot weather?
In hot environment more glycogen is utilized due to higher amounts of plasma adrenaline and higher muscle temperatures
What happens to lactate production when exercising in warmer temperatures?
Lactate production is higher in hot temperatures
Why does the body work exert less during times of hot temperatures?
Higher body temperature decreases performance to keep temperature stable.
What is the result of lower core temperature?
Longer exercise time
What happens to exercise time in preheated athletes?
preheating athletes before exercise decreases exercise time and vice versa.
What are the central fatigue mechanisms that are affected by exercise-heat stress?
increase in rated percieved exertion
Reduced voluntary activation of muscle
Reduced cerebral blood flow but increased VO2.
Hyperprolactinaemia (increase in prolactin associated with fatigue)
What is the central mechanism to avoid too much heat production?
reduced neuromuscular performance with hyperthermia. The brain increases inhibitory signals to muscles to avoid too much heat productio from muscles
What are the physiological and metabolic adaptations to heat acclimatisation?
Increase in blood volume
Reduced heart rate
Lower skin and core temperature
Increased sweat rate and earlier onset of sweat
more diute sweat
Reduced muscle glycogen use
What happens to hyperthermia if fluids are replaced during exercise?
hyperthermia’s effect is attenuated by fluid replacement.
What is the effect of dehydration on exercise performance?
Prior dehydration impairs exercise performance. This is due to decreased central cardiovascular function.
What are the benefits of fluid ingestion during exercise?
Increased blood volume
lower heart rate
increased stroke volume and cardiac output
lower core temperature
lower plasma sodium and osmolality
reduced muscle glycogen use
enhanced exercise performance
What is the function of renin and aldosterone?
fluid and salt retention
Is decrease in exercise time due to excess glycogen utilization that occurs in warmer temperatures?
No
