L19-20: Exercise physiology Flashcards
What is the difference in VO2 response for untrained and trained individuals?
Untrained t= 30-45 s
Trained t= <20s
What is the definition of VO2 max?
The maximal amount of oxygen delivered to the wiring tissues and utilised in aerobic metabolism
What is VO2 a measure of?
Rate of aerobic metabolism
How does exercise impact VO2?
And increase in exercise generated an increased O2 demand which results in an increase in VO2
What are the utilisation and presentation theories?
Utilisation: VO2 max is determined by body ability to utilise available oxygen
Presentation: VO2 max is the ability of the body’s CVS to deliver oxygen to active tissues
What is included in a graded exercise test?
Uses large muscle groups
Running/cycling/rowing
Optimal test length 8-10 mins
Direct test of maximal aerobic power
Increase load stepwise every 1-4 mins until subject cannot maintain desired work rate (ramp protocol, square-wave tests)
(ramp protocol better, higher correlation between VO2 and workload)
What is the ventilatory response to exercise?
Immediate increase in ventilation mediated by feed forward reflex. Proprioreceptors in muscles and joins to motor cortex to respiratory centre increase ventilation before change in alveolar PO2 and PCO2
Ventilation rate controlled by changes mediated by peripheral and central chemoreceptors, rise in K+ too
At cessation of exercise ventilation rate remains elevated until ATP and CP stores return to normal
Why is minute ventilation needed during exercise?
To compensate for the increase in oxygen demand, to get more oxygen into the body
What is the result of an increase in ventilation?
Increased diffusion capacity due to increased blood flow through lungs and tissue, increased systolic blood pressure and changes in blood flow distribution
What is the relationship between work rate and minute ventilation?
Ventilation increases with increase in work, at ~70% max exercise ventilation increases rapidly
How is respiration driven when work rate and minute ventilation reaches threshold?
pH drives respiration (respiratory compensation for metabolic acidosis)
What is ventilatory threshold?
The point during exercise at which ventilation starts to increase at a faster rate than VO2
What does ventilatory threshold show?
Levels of anaerobiosis and lactate accumulation
What happens to cardiac output during exercise?
Heart rate increases
Stroke volume increases
Cardiac output increases
What is the effect of cardiac output on exercise?
CO is a measure of blood flow/ min
Rest CO=5-6 L/min
CO increases linearly with the demand for more O2
CO can reach 25-30L/min in trained athlete
CO plateaus at very high work loads
What is the effect of exercise on heart rate?
Increases with intensity and levels of maximal effort
Increase mediated by increased sympathetic activation of SA node and decreased sympathetic output
How is stroke volume controlled during exercise?
Increases with intensity
Increases linearly with demand for more O2
Dips at extremes due to shortened filling time at high HR
What are the mechanisms that are responsible for an increase in stroke volume?
Increased contractility of heart mediated by increased sympathetic output and circulating adrenaline
Increased End Diastolic Volume from (sympathetic vasoconstriction, skeletal muscle pump, respiratory pump)
Decreased after load
How does an athlete achieve a large max CO through a large SV?
Changes in cardiac dimensions, blood volume and venous return
Mechanism: enhanced diastolic filling, grater systolic emptying, blood volume expansion & reduced resistance to blood flow, decreased sympathetic drive
Increased SV via increased ventricular filling and emptying
