Environmental Conditions - Heat Flashcards
Types of temperature
Ambient temperature
The temperature of the environment the athlete is performing in
Core temperature
The temperature inside the athlete’s body
thermoregulation with blood
Vasodilation
When the body needs to loose heat
The blood vessels near the skin increase heir diameter which increases blood flow to the skin so heat loss can occur
Vasoconstriction
When the body needs to conserve heat
The blood vessels near the skin decrease their diameter which decreases the blood flow to the skin so less heat is lost
methods of heat gain
Hormones
Environment
Muscular activity
Basal metabolic rate
Methods of heat loss
Radiation
Conduction
Convection
Evaporation
Radiation
Heat is transferred from a warmer body to cooler surroundings without physical contact
If the core temperature is higher than ambient temperature, heat is lost
If the core temperature is lower than the ambient temperature, heat is gained
Conduction
Heat exchanged by 2 objects in contact
Factors that affect the conduction rate
Difference in temperature (hot-
>cold)
Surface area (^SA = ^heat loss)
Thermal conductivity of material
Convection
Heat exchange by contact with a fluid that is flowing
This will occur when heat is carried away by air or ocean currents
Magnitude of heat loss depends on the speed and temperature of the fluid
Heat loss will occur faster as the
breeze strengthen
Evaporation
Is the cooling of the body as a result of the evaporation
To avoid overheating, the body uses blood to help regulate temperature
Heat is transferred to the skins surface via the blood, where it is released as sweat
preferred method of heat loss factors
envrionment
age
physiological state
environment
Ambient temperature
If above the core body’s temperature, evaporation is the only method of heat loss
Forced convection
Heat loss via convection will occur if it is windy
Barriers to convection
Clothing will minimise the effect of convection as it will insulate the boundry layer of air
Temperature radiating surfaces
Lighter clothing will not absorb as much heat as dark clothing
Relative humidity
If 100%, no heat loss via evaporation
age
Children don’t sweat as much as their sweat glands aren’t as developed as adults
physiological state
Rate of heat production
Hydration state
Will determine the rate of evaporation as a reduction in plasma volume leads to a decrease in sweat rate
dehydration
Occurs when the amount of water leaving the body is greater than the amount being taken in
We loose water by;
Breathing
Sweating
Urination or bowel movements
Double heat load
When exercising in the heat, the body is forced to deal with 2 forms of heat, known as double heat load
Metabolic heat created by the muscles
Environmental heat in hot conditions
As a result of this:
Muscles and vital organs require blood flow to sustain energy metabolism
Skin blood flow is required to transport heat to the environment to keep the core cool
cardiovascular drift
When exercising In the heat, the body directs blood flow to the skin and away from the working muscles to increase heat loss
An increase in sweat rate will decrease the blood plasma volume
As a result cardiovascular drift occurs:
To maintain cardiac output, the heart rate increases
This increase in heart rate is relatively smaller than the decrease of stroke volume, so cardiac output is reduced
As a result, the blood flow to the skin is decreases and oxygen is sent to the working muscles are also reduce, which places extra strain on the body
Hyperthermia
If the body becomes too hot
Skin blood vessels will vasodilate so more blood flow to the skin
You sweat until you cant sweat anymore and then core temperature increase
Heat acclimatisation
When heat tolerance is improved by repeated exposure to hot environments
Adequate hydration is required for optimal heat acclimatisation
Exposure to thermal stress is a major concern for athletes in hot climates
How to acclimatise (how long/where/when)
How long?
The first sessions should last 15-20 mins with only light activity
should increase to 45-60min daily
5-10 days of living and training in the heat is recommending
Where?
Athletes who are unable to use natural acclimatisation should use
Artificial heat sources
Climate chambers
Saunas
Sweat clothing
When?
4-6 weeks before competition and then 2x per week to maintain benefits leading up to the competitions
major adaptations
sweating
cardiovascular
sweating
Increased blood plasma volume
More fluid is stored in the blood
Increases length of time to dehydration
Increased sweat rate
Start sweating at a lower core temperature
Sweat becomes more dilute and distributed more effectively over the body
cardiovascular
Athletes heart rate is lower as they have a more efficient cooling mechanism
A lower core temperature also reduces the body’s need to send blood to the skin for cooling
Increased blood volume to allow for increased sweating
strategies to cope with heat
Hydration
600ml 3-4hrs before
200ml 20 mins tomorrow
Consume 1.5x weight loss post
Clothing
Wear loose-fitting, light coloured clothing to permit free air circulation between the skin and the environment
Pre-cool body
Use ice vests/towels
Drink a slushie
Immersion in cool water
Acclimatise
Protection from the sun
Reduce the length of warm-up and limit exposure to the sun
