5.3. Heat Effects and Acclimatisation

Question 1

Thermoregulation

Answer 1

The process of maintaining internal temps

Question 2

Thermoreceptors

Answer 2

Sense a change in temp and relay info to the brain

Question 3

Hyperthermia

Answer 3

Significantly raised core body temp

Question 4

Dehydration

Answer 4

Loss of water in body tissues and blood, leads to inability to control temp

Question 5

What defense mechanisms does the hypothalamus activate?

Answer 5

1. evaporative techniques (sweating)
2. non evaporative techniques (cooling of blood at skin)

Question 6

What happens in sweating?

Answer 6

• the hypothalamus stimulates the sweat glands
• increased sweat production
• sweat evaporated from the skin to provide cooling
• decreased volume of blood plasma
• less blood returns to the heart (VR) = reduced SV, blood pressure drops
• HR increases to maintain o2 delivery to muscles
• leads to cardiovascular drift

Question 7

What happens in cooling of the blood at the skin?

Answer 7

• increased volume of blood to skin
• redistribution of blood to skin from muscles and organs
• vasodilation of arterioles and pre-capillary sphincters at the surface of the skin
• blood pooling at the skin occurs
• causing a decrease in VR
• according to Starling’s law, if VR decreases, SV decreases
• less blood to deliver o2 to muscles
• HR increases to maintain Q and maintain o2 delivery to muscles
• leads to cardiovascular drift

Question 8

What are the effects of heat on the respiratory system?

Answer 8

• drying of airways = constriction of airways = less air for gas exchange
• increased mucus production to moisten airways = reduced air flow
• increased breathing frequency to maintain exercise intensity = increased energy ‘cost of exercise

Question 9

What are the effects of heat on performance?

Answer 9

Decreased efficiency of CV and respiratory leads to thermal strain which means it’s likely an athlete will move towards anaerobic energy production leading to OBLA and earlier fatigue.

Maximal and explosive strength activities are unaffected by heat or may gain a slight advantage (due to lower air density)

Endurance sports are most affected by the rise in HR and breathing rate causing fatigue.

• dehydration = decreased performance

Question 10

What is heat stress disorder?

Answer 10

• if temp cannot be controlled it can lead to heat stress disorders

Question 11

What is heat cramp?

Answer 11

due to dehydration and loss of electrolytes

Question 12

What is heat stroke?

Answer 12

second only to head/ spine injuries as no1 cause of death in athletes. Symptoms include cramps, muscle pain.

Question 13

What is heat exhaustion?

Answer 13

CV system is unable to meet the demands of muscles and skin due to loss of blood volume through sweating, therefore can’t cool down or exercise.

Symptoms include sickness, dizziness, breathlessness, high HR, numbness in hands and feet.

Can lead to death or permanent damage to brain/ organs if body unable to reduce body temp.

Question 14

What happens after 3-5 days in heat?

Answer 14

• heat tolerance improves
• a decrease in core body temperature
• an increase in blood plasma volume
• decrease in HR

Question 15

What happens after 2 weeks acclimatisation?

Answer 15

• an increase in sweat rate
• increase in evaporative techniques without electrolyte loss.

Question 16

Strategies pre comp for competing in heat

Answer 16

• 7-10 days acclimatisation
• ice vests - use cooling aid to decrease core body temp and decrease sweating

Question 17

Strategies during comp for competing in heat

Answer 17

• using pacing strategies to reduce exertion
• wear suitable clothing that maximises heat loss
• rehydrate to replace fluids and electrolytes

Question 18

Strategies post comp for competing in heat

Answer 18

• cooling aids- cold towels and fans
• rehydrate to replace electrolytes and fluids