Lecture 14

Question 1

Why is heat dissipation necessary?

Answer 1

Heat dissipation is to avoid critical hyperthermia

Question 2

What are the 4 mechanisms of heat loss during exercise?

Answer 2

conduction

Convection

radiation

evaporation

Question 3

What is the problem with humid conditions?

Answer 3

High humidity conditions prevent evaporation due to water vapour pressure gradient.

Question 4

What happens to core temperature during exercise?

Answer 4

Core temperature increases during exercise and levels off eventually. Heat loss mechanisms take time to kick in

Question 5

What 3 mechanisms correlate with exercise intensity?

Answer 5

Sweating

Heat production

VO2 max

Question 6

Is sweat hypo or hyper tonic to plasma?

Answer 6

Sweat is hypotonic to blood plasma

Question 7

Can sweat glands reabsorb sodium?

Answer 7

Yes

Question 8

Why do trained individuals have less sodium in their sweat?

Answer 8

Trained individuals have less sodium in sweat due to increased sodium reabsorption as a response to aldosterone,

Question 9

What happens to cardiac output during exercise and why does this happen?

Answer 9

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.

Question 10

What happens to glycogen utilization during exercise in hot weather?

Answer 10

In hot environment more glycogen is utilized due to higher amounts of plasma adrenaline and higher muscle temperatures

Question 11

What happens to lactate production when exercising in warmer temperatures?

Answer 11

Lactate production is higher in hot temperatures

Question 12

Why does the body work exert less during times of hot temperatures?

Answer 12

Higher body temperature decreases performance to keep temperature stable.

Question 13

What is the result of lower core temperature?

Answer 13

Longer exercise time

Question 14

What happens to exercise time in preheated athletes?

Answer 14

preheating athletes before exercise decreases exercise time and vice versa.

Question 15

What are the central fatigue mechanisms that are affected by exercise-heat stress?

Answer 15

increase in rated percieved exertion

Reduced voluntary activation of muscle

Reduced cerebral blood flow but increased VO2.

Hyperprolactinaemia (increase in prolactin associated with fatigue)

Question 16

What is the central mechanism to avoid too much heat production?

Answer 16

reduced neuromuscular performance with hyperthermia. The brain increases inhibitory signals to muscles to avoid too much heat productio from muscles

Question 17

What are the physiological and metabolic adaptations to heat acclimatisation?

Answer 17

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

Question 18

What happens to hyperthermia if fluids are replaced during exercise?

Answer 18

hyperthermia’s effect is attenuated by fluid replacement.

Question 19

What is the effect of dehydration on exercise performance?

Answer 19

Prior dehydration impairs exercise performance. This is due to decreased central cardiovascular function.

Question 20

What are the benefits of fluid ingestion during exercise?

Answer 20

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

Question 21

What is the function of renin and aldosterone?

Answer 21

fluid and salt retention

Question 22

Is decrease in exercise time due to excess glycogen utilization that occurs in warmer temperatures?

Answer 22

No