Heat adaptations

Question 1

How does HA affect exercise performance in cooler conditions?

Answer 1

• Max Q increased in cool conditions following HA.
• Increased VO2 max reported after HA.
• Increase in VO2 max decreases relative exercise intensity at any given work rate.
  > Augmented by improved exercise economy in cool conditions following HA.

Question 2

What is the relationship between heat and running performance?

Answer 2

In hot temperatures running performance improves in short distance events. In long distance events hot temperatures cause a decrease to performance.

Question 3

What are the 4 heat loss effector mechanisms?

Answer 3

1) Conduction
2) Convection
3) Radiation
4) Sweat evaporation

Question 4

What is conduction?

Answer 4

• Transfer of heat from the body to an object which is in direct contact e.g. heat transfer when sitting on a chair.
• 3% of total heat loss at rest at normal room temperature.

Question 5

What is convection?

Answer 5

• The conduction of heat to or from air or water.

- 12% of total heat loss at rest at normal room temperature.

Question 6

What is radiation?

Answer 6

• Transfer of heat in the form of electromagnetic waves.

- 60% of total heat loss at rest at normal room temperatures.

Question 7

What is sweat evaporation?

Answer 7

• When 1g of sweat changes from water to vapour the body loses 2.41KJ of energy.
• 25% of total heat loss at rest at normal room temperature.
• Progressively more important at higher temperatures.

Question 8

What happens to skin blood flow during exercise?

Answer 8

During exercise skin blood flow is:

• Reduced
• Exhibits a delayed response
• Attains a sub-maximal plateau

Question 9

What are cardiovascular consequences of hyperthermia?

Answer 9

• Decreased Q and increased HR = less blood pumped by the heart = cardiovascular drift.
• Decreased blood pressure + increased total peripheral resistance = Decreased muscle blood flow.

Question 10

What are the metabolic consequences of dehydration?

Answer 10

• Decreased Q
• = decreased VO2 max
• Dehydration causes a fall in plasma volume.
• Decreased blood volume increases viscosity.
  ↘︎ Lowers central nervous venous pressure.
  ↘︎ Reduces venous return of blood to the heart.
• Decreased VO2max leads to increased anaerobic metabolism contribution.
• increase lactic acid production.
• Increase muscle glycogen utilisation
  = accelerated fatigue.

Question 11

How does hyperthermia enhance sprint/power events?

Answer 11

• Decrease resistance of muscles and joints.
• Faster nerve conduction velocity.
• Improvements in muscle contractile apparatus.
• Faster metabolic reactions.
  ↘︎ For every 10% increase in temp, metabolic rate is doubled.
• Increased sympathetic nervous system activity.
  ↘︎ Increased adrenaline and noradrenaline.
  ↘︎ Increased glycogenolysis.

Question 12

Methods to attenuate hyperthermia

Answer 12

• Fluid replacement strategies.
• Cooling interventions before or during exercise.
• Heat adaptation → Most important intervention to reduce physiological strain and optimise performance.

Question 13

What are the main two forms of heat adaptation?

Answer 13

• Heat acclimation (artificially induced heat adaptation) e.g. environmental chamber.
• Heat acclimatisation (natural exposures) e.g. warm weather training camps.

Question 14

What are the 3 types of HA time frames?

Answer 14

• Short term heat adaptation (<7 exposures)
• Mid term heat adaptation (8-14 exposures)
• Long term heat adaptation (>15 exposures)

Question 15

What are the 7 key variables to complete heat adaptation?

Answer 15

Lower:

• HR
• SV
• Sodium loss
• Urine loss
• Water loss
• higher Sweat Rate
• Reduced Skin blood flow

Question 16

List effects of heat acclimation

Answer 16

• Improved ability to get rid of excess body heat.
• Decreased body core temperature for a given sub-maximal work rate.
• Sweating increases and becomes more dilute.
• Blood flow to skin is reduced; more blood available to muscles.
• Attenuated HR.
• SV is maintained.

Question 17

Describe the relationship between HA and HR.

Answer 17

• HA results in lowered resting and mean HR.
• Most HR adaptations take roughly 7 days.
• HR could be used as a simple way to set workloads which ensure a sufficient thermal impulse is maintained for effective heat adaptation.

Question 18

Describe the relationship between HA and sweat response.

Answer 18

• Changes in the onset temperature at which sweating commences (sudomotor threshold), changes in capacity of sweat glands.
• HA reduces sudomotor threshold.
• Total sweat loss increased following HA.