Week 13 - Environment and Exercise Performance Flashcards
What is humidity?
The amount of water vapour in the air
What is normal core body temperature?
37 degrees
What part of the brain regulates body temperature control?
Hypothalamus
Identify ways the hypothalamus can control body temperature?
Can stimulate the cerebral cortex to make behavioural changes
- E.g. down regulate the intensity of activity to lower the metabolic rate of heat production
- Remove excess clothing etc
Can impact physiological systems
- Can stimulate sweat glans
- Affect arterioles (vasodilate or constrict)
- Stimulate skeletal muscle (To initiate shivering to generate more body heat to stay warm in cold environments)
How do hot and cold receptors regulate body temperature?
Where do each peak?
Warm Receptors
Peak around 40-45 degrees
Cold Receptors
Peak around 25 degrees
The peak in the cold and warm receptors is important so they are responsive to small deviations in the conditions we’re exposed too –> helps to regulate precise control
What is the most effective way to dissipate heat?
Sweating
Where are sweat rates highest and lowest?
Explain why
Sweat rates tend to be high on the forehead or on the chest or back
- High on the forehead because the evaporation from the head will keep the head/brain cool –> very sensitive to temp changes
- High sweat rates on chest and back is advantageous because it is a large muscle group –> large surface area and more likely to evaporate
Sweat rates are lower in hands or feet
How does evaporative cooling work?
Evaporation works down a humidity gradient, so it goes from an area of high humidity to an area of lower humidity
How would a Dry VS humid environment alter sweat evaporation?
Dry = Larger humidity gradient between skin and environment
- Better evaporative cooling properties
Humid = can’t readily evaporate because the gradient is smaller
How do trained athletes better tolerate hot environments?
Physiological adaptions that occur
Higher CO –> preserve the blood flow to the gut etc while still getting enough to the working muscles
Many other reasons too
What are some symptoms of heat stroke?
- Headache
- Disorientation
- Nausea
- Excessive thirst
- Rapid pulse
- Confusion
What are the 4 ways we lose/gain heat?
- Convection
- In context of running the air flows across the skin
- Will result in heat loss if air temp is lower than body temp - Evaporation (most effective)
- Conduction –> negligable during exercise
- Radiation –> Suns out and very hot higher than temp of us so we gain radiant heat from the sun and will add to our heat gain
What happens to blood distribution during ambient temp vs hot temp
Relate to muscle and skin delivery
Ambient
- More blood to the working muscle and less to the skin
- To be able to maintain the workload
Hot environment
- More blood flow to the skin
- Lower proportion is delivered to the muscle
- This helps to dissipate heat
How does Heat stress cause CV strain?
- Increase in HR for same relative intensity of exercise in hot conditions vs cooler conditions
- This is because blood not only needs to be pumped to muscles it also needs to go to skin –> meaning CO has to increase to meet the demands of the exercise
- CV drift during extended periods of exercise
- As we progressively become dehydrated plasma volume decreases thus decrease CO –> HR has to increase to maintain CO
Physiological adaptation to heat acclimation?
Increased Sweating: Helps maintain body temperature and allows better blood flow to muscles (if fluids are replenished).
Lower Peak Heart Rate: Declines by up to 30 beats, reducing cardiovascular strain.
Lower Peak Core Temperature: Body heats up less during exercise.
Earlier and More Sweating: Sweating starts earlier and at higher rates for increased heat loss via evaporation.
Improved Skin Blood Flow: Blood is directed to the skin earlier for better heat dissipation.
Increased Plasma Volume: Reduces dehydration risk, supports stroke volume, and helps maintain blood pressure.
