what is vasodilation?
increase size
what is vasoconstriction?
decrease size
4 ways of gaining heat?
hormones
environment
muscular activity
metabolic rate
4 ways of losing heat?
what is double heat load?
Heat is produced within the muscles when they are working, and also is present in the environment
conduction?
is the heat exchanged by two objects that are in contact with each other.
convection?
is heat exchange by contact between an object and fluid that is flowing. This occurs when heat is carried away from the body by air or water currents.
radiation?
occurs when heat is transferred from a warmer body to the cooler surroundings without physical contact.
evaporation?
is the cooling of the body as a result of the vaporisation of sweat.
what effects the rate of sweat?
Gender (males sweat more than females)
The number of sweat glands
Body surface area (Increased SA increased sweating)
How fit they are (Increased fitness increased sweating
factors affecting conduction?
Difference in temperature between the two objects (heat flows from hot to cold)
Surface area (Increased surface area increased heat loss)
Thermal conductivity of material (e.g. metal is a good conductor of heat)
factors affecting convention?
The speed and temperature of the air/water. E.g. if a breeze gets stronger, the heat loss occurs faster.
The layer of warm air that continually surrounds our body is displaced by cold air when air temperature is lower than skin temperature
heat loss by exposing more of their body surface area to the cooler surrounds
factors affecting radiation?
Radiation accounts for 60% of heat loss from body at rest on a cool day.
explaining evaporation? (4)
excessive sweating
Excessive sweating leads to a loss of body fluids, and when level of body fluid drops, the body’s core temperature increases.
It is this gradual dehydration that leads to heat exhaustion and heatstroke.
Sweat loss can reach 6 – 10% of body mass
> 2% generally means performance and thermoregulation are compromised
3 ways of heat transfer
dehydration
occurs when the amount of water leaving the body is greater than the amount of water being taken in.
cardiac drfit (explanation)
creates a competition for blood flow.
hyper-hydration
Involves increasing the body’s fluid stores by consuming extra fluid prior to an event
pre exercise how much water
1L prior to exercise is recommended
600ml 3 – 4 hours before game/competition
400ml just prior to game to prime the stomach
Avoid caffeine – it is a diuretic & increases fluid loss
Allows the athlete to sweat more before performance is inhibited
water during exercise
Drink ~200ml of water every 15 minutes during activity. This is influenced by environmental conditions and exercise intensity.
water post exercise
Want to replenish back to pre-exercise weight
For every litre of sweat loss, consume
1.5L as you will lose some of this through urine
Consume slightly salty fluid to keep osmolality higher so you don’t urinate as much.
hyponatremia
is an abnormally low concentration of sodium (salt/electrolytes) in the blood
what is heat acclimatization
is when heat tolerance is improved by repeated exposure to hot environments.