8 Thermoregulation during exercise and performance in the heat

Question 1

Elevated body temperature during exercise, a result of?

Answer 1

It is generally assumed that elevated body temperatures in muscular work are due to failure of heat regulation

Question 2

Heat production overcomes heat loss at what intensity?

Answer 2

Approx 60 Watts

Question 3

Thermoregulation and gender

Answer 3

-In the heat, men sweat more and sooner than women and have a lower
Tcore
- In cold, women shiver less, cool slower and have a lower body temperature than men
-During exercise, sweating rate is lower in women

Question 4

Approximate energy output from rest to exercise

Answer 4

5-7 kJ.min-1 to 75-90 kJ.min-1

Question 5

Time to exhaustion during continuous exercise is decreased in heat:

Answer 5

At 70% VO2max:

• 51.6 min in 30.5°C
• 93.5 min in 10.5°C

Active or passive pre-warming decreased time to
exhaustion in moderate environment.

Question 6

Causes of fatigue

Answer 6

Exercise and heat -> hyperthermia -> circulation fluid balance -> Fatigue

Hyperthermia -> Metabolism and muscle function -> fatigue

Question 7

Hyperthermia on fatigue

Answer 7

Fatigue occurs at same level of hyperthermia independent of starting body temperature and rate of heat storage.

Question 8

Decreased performance in the heat is due to many

inter-related factors:

Answer 8

• Hyperthermia
• Hypohydration
• Decreased muscle function
• Increased cardiac strain
• Central fatigue

Question 9

How to improve exercise performance in heat:

Answer 9

• Fluid ingestion
• Pre-cooling
• Heat acclimation