Exercise Physiology: Oxygen, Heat and Fluids Flashcards
What is oxygen uptake in exercise dependent on?
Intensity of exercise
What are the cardiovascular responses to exercise?
Increase oxygen supply to skeletal and cardiac muscle
Facilitate carbon dioxide and heat removal
Maintain mean arterial pressure
What is Fick’s equation?
VO2 = cardiac output * (CaO2 - CvO2)
Which organ extracts most of the oxygen from arterial blood during exercise?
Skeletal muscle
Why can you get post-exercise hypotension?
Finish exercise > sudden drop in cardiac output > vessels in legs still dilated > blood pools in legs
Why does the skin vasoconstrict during intense exercise, and why can this be dangerous?
Muscle vasodilates > skin vasoconstricts to increase total peripheral resistance and maintain mean arterial pressure
Dangerous because vasoconstriction of skin decreases heat loss
What is exercise hyperaemia?
Increase in blood flow to muscles during exercise
What causes exercise hyperaemia?
Metabolic vasodilators from contracting skeletal muscle, endothelium, and/or red blood cells
Muscle pump
Conducted vasodilation
Functional sympatholysis
What is conducted vasodilation?
Gap junctions spread vasodilation, especially upstream to larger arterioles
What is functional sympatholysis?
Alpha receptors on blood vessels normally cause vasoconstriction when activated
Become less effective in exercise because metabolites desensitise them
What is the difference between cardiac output between an athlete and a sedentary person for any given VO2?
Not much difference
What is the difference between the heart rate of an athlete and a sedentary person for any given VO2?
Lower in athlete
What is the difference between the stroke volume of an athlete and a sedentary person for any given VO2?
Higher in athlete
What happens to blood pressure during exercise, and why?
Decreased time in diastole, so systole happens more often > increase in blood pressure
What happens to the baroreflex during exercise, and why?
Resets to higher level to allow increase in heart rate with increased blood pressure
What is cardiovascular drift during prolonged exercise?
Increased heart rate and decreased stroke volume
Why does cardiovascular drift occur during prolonged exercise?
Hyperthermia
Dehydration
Increased plasma adrenaline
Peripheral displacement of blood volume due to cutaneous vasodilation
Why is heart rate lower with exercise in water?
Blood stays more central
What changes occur in the neural control of circulation during exercise?
Increased heart rate in anticipation
Resetting of baroreceptor reflex
How does autonomic control increase heart rate during exercise?
Early rise because of vagal control
Later, increases because of sympathetic control
Why does cardiac output increase after training?
Expanded blood volume
Increased heart size
Increased adrenergic sensitivity
Why does heart size increase after training?
Increased left ventricle mass and chamber size
What microvascular adaptations occur after exercise training?
Increased capillary density
Increased capillary recruitment
What are the respiratory responses to exercise?
Maintain arterial oxygen saturation
Carbon dioxide removal
Acid-base balance
What proportion of arterial blood is saturated during exercise at sea level in healthy individuals?
Fully oxygenated
Under what conditions does arterial desaturation occur during exercise?
High altitude
Why may highly trained athletes have arterial desaturation?
Cardiac output may be too fast to fully oxygenate blood
What is the main mechanism of heat loss during exercise?
Sweating
When is sweating not as effective?
Humid weather
What is the relationship between heat stress and exercise capacity and performance?
Heat stress impairs exercise capacity and performance
What body fluid compartments are affected in exercise-induced dehydration?
All
What is the relationship between dehydration during exercise and performance?
Dehydration impairs performance
What is the relationship between exercise performance and prior dehydration?
Prior dehydration impairs exercise performance
