Week 8 - Thermoregulation and Heat Stress Flashcards
Whats the normal body resting tempreature
36.5-37.5 celsius
Whats core body temperature defined as
Temperature of the hypothalamus, the thermoregulatory centre of the body
How is heat loss physiologically controlled
- Body temperature increase is detected
- Blood vessels dilate, sweat glands secrete fluid and heat is lost.
- This results in heat being lost to the environement
- Then body returns back to normal temperature
How is heat retention physiologically controlled
- Body temperature falls.
- Blood vessles constrict, sweat glands do not secrete fluid and heat is conserved. Shivering generates heat so heat is generated
- Heat is then retained as a result
- Body temperature returns to normal level
How is the heat balance/body temperature maintained
Maintained by balancing heat gain and heat loss
What are some examples of heat conservation/production
Shivering thermogenesis
Voluntary muscular activity
Non-shivering thermogensis
What are some examples of heat loss
Blood reaching the skin
Sweating
Whats a key difference between skin and core temperature
Unlike core temperature, skin temperature is not regulated and varies across the body in response to the thermal environment
Whats the effect of hot humid environments on aerobic performance
Its impaired
Why is aerobic performance effected in hot conditions
There is an increase demand on heat loss mechanisms such as skin blood flow and sweating. There is a reduced gradient between core and skin so therefore core temperature increases
How does dehydration impact heat stress
Decreases sweat rate and plasma volume.
Also a further decrease in cardiac output, maximal oxygen uptake, muscle strength and work capacity
Why is pro-longed high intensity training in hot conditions significantly impaired
This is because there are competing regulatory demands for blood flow between thermoregulation, working muscle and CNS
Also heat-related changes in skeletal muscle function and metabolism
Whats the most rapid way to lower body temperature
Cold water immersion is the most rapid way to lower body temperature
How can you mitigate the impact of heat stress before, immediately before and during exercise
(ON SHEET)
Before - heat acclimation and aerobic training
Immediately before - pre-cooling, hydration status
During - Hydration, clothing and cooling
How effect of the acclimatisation response of improved cutaneous blood flow
Transports metabolic heat from deep tissue to shell
How effect of the acclimatisation response of effective distribution of cardiac output
Appropritate circulation to skin and muscle to meet demands; greater blood pressure stability during exercise
How effect of the acclimatisation response of lowered threshold for start of sweating
Evaporative cooling begins early in exercise
How effect of the acclimatisation response of more effective distribution of sweat over skin surface
Optimum use of effective body surface for evaporative cooling
How effect of the acclimatisation response of increased sweat output
Maximises evaporative cooling
How effect of the acclimatisation response of lowered salt concentration of sweat
Dilute sweat preserves electrolytes in extraceullular fluid
How effect of the acclimatisation response of lower skin and core temperatures and heart rate for standard exercise
Frees greater proportion of cardiac output to the active muscles
How effect of the acclimatisation response of less reliance on carbohydrate catabolism during exercise
Carbohydrate sparing
What is hypothermia
When heat loss exceeds heat production (conduction, convection, radiation and evaporation) and core temperature drops below 35 celsius.
Whats the effects of drops in temperature measuremtns - 2 4 and 6 degrees
2 degrees - maximal shivering
4 degrees - ataxia and apathy
6 degrees - unconsciousness
Further drop associated with ventricular fibrillation, reduced brain blood flow, asystole and death
Whats the effect of cold on exercise performance
Due to shivering oxygen consumption is higher in cold water during sub-maximal exercise but reduced during maximal exercise
What is the physiological effect to the increased submaximal vo2 in cold exercise
Greater heat loss
What is the physiological effect to the decreased exercise capacity in water in cold exercise
Greater heat loss
What is the physiological effect to the Increased ventilation during submaximal exercise in the cold exercise
Increased sympathetic stimulation
What is the physiological effect to the Reduced skin blood flow in cold exercise
Peripheral vasoconstriction
What is the physiological effect to the lower lipid mobilisation in cold exercise
reduced blood flow to adipocytes
What is the physiological effect to the increased lactate concentration in cold exercise
Increased carbohydrate metabolism
What is the physiological effect to the Increased central blood volume in cold exercise
Peripheral vasoconstriction
What is the physiological effect to the decreased heart rate during submaximal exercise in cold exercise
Increased central blood volume
What is the physiological effect to the release of leptin from adipose tissue in cold exercise
Increased sympathetic stimulation
What happens as a result of cold acclimatisation/acclimation
Results in lower skin temperature at which shivering begins - increased non-shivering thermogenesis.
Maintains higher hand and foot temperature - improved peripheral blood flow
Improved ability to sleep in the cold - due to reduced shivering
Adaptations begin in one week
