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
