Cardiovascular Response to Exercise (S1W2) Flashcards
Which of these factors are responsive to exercise training?
a. maximum heart rate
b. heart size
c. blood volume
d. haematocirt
- heart size
- blood volume
- haematocrit
max heart rate isn’t trainable
haematocrit doesn’t respond that much to training
Why does the cardiovascular system adapt to exercise? Acutely
- To increase O2 delivery to working muscles by increasing blood flow to the muscles and reducing delivery to low activity tissues
Why does the cardiovascular system adapt to exercise? Chronically
- To deliver more O2 to active muscle mass: more effective O2 delivery during sub-maximal exercise and increase maximum O2 consumption (VO2 Max)
What cardiovascular factors influence oxygen uptake and VO2 max?
- Cardiac (heart) structure and function
- Blood (plasma) volume
- Blood flow and distribution
- O2 extraction (arterio-venous difference)
What is arterio-venous difference?
- The difference in the oxygen content of the blood between the arterial blood and the venous blood
- An indication of how much oxygen is removed from the blood in capillaries as the blood circulates in the body
(What factors influence oxygen uptake and VO2 max?) Explain how oxygen extraction is done.
- Needle going into an artery - measures the O2 content in the artery (O2 content in blood as it leaves the heart)
- Puncture a vein coming back from the tissue of interest (e.g. leg)
- Any difference between the O2 content tells us how much O2 has been taken up by the muscle
Fick equation
- VO2 = HR x SV x (a-v)O2 difference
- HR –> heart rate
- SV –> stroke volume
- a-v –> arterio-mixed venous
- Q –> cardiac output (HR x SV)
Explain the relevance of stroke volume in the Fick equation
- If arterio-mixed venous difference is multiplied by the heart rate and stroke volume, it will tell you how much O2 uptake there is in the whole body
How is stroke volume measured?
- SV measured with an ultrasound (check dimension of the heart)
Adapting to exercise training: How is ventricular mass relevant?
- A good indicator of training status
- Untrained = lighter heart
Heart structure: key descriptors
- Left ventricular mass (muscle bulk of the left ventricle)
- Septum - provides muscle mass
- Left ventricular volume (how much blood fits in the ventricle)
- Left ventricular wall thickness - provides muscle mass
True or False? Endurance athletes have larger hearts than controls
True
True or False? Power athletes have more muscular hearts than endurance athletes
True
True or False? Endurance athletes have smaller hearts than power athletes
False
True or False? Endurance athletes have more muscular hearts than controls
True but not by much, power athletes vary more from controls in terms of how muscular their hearts are.
Explain what preload is
- The amount of blood in the ventricle before contraction (end diastolic volume)
- This determines cardiac muscle length before contraction
- The most important determining factor for preload is venous return
Preload: aortic and pulmonary valves
- Aortic valve goes into periphery and the pulmonary valve goes into the lungs
- If these valves are closed, the heart is being filled (associated with pre-load - how much blood can fit into the heart) (diastole)
Preload: mitral and tricuspid valves
- If mitral and tricuspid valves are closed, the filling is complete and the aortic and pulmonary valves open, so blood can go into lungs and periphery (systole)
Explain what afterload is
- The pressure against which the heart must contract (vascular resistance, aortic mean pressure)
- The higher the afterload, the less blood will be ejected per beat
What is contractility?
- the force that the heart creates
Contractility: Explain what the Frank-Starling mechanism is
- Based on the length-tension relationship within the ventricle (the greater the stretch, the greater the contraction)
- If ventricular end diastolic volume (preload) is increased, the ventricular fibre length is also increased, resulting in an increased tension of the muscle
- The more full the heart is, the harder it can contract
- The longer the muscle fibre is, the more it can contract
What is an athlete’s heart like?
- Left ventricular mass is heavier in all athletes
- Left ventricular volume is larger in endurance athletes
- Posterior wall thickness and septal thickness is larger in resistance athletes
Endurance athlete’s hearts: why do they have larger stroke volumes?
- High preload and eccentric hypertrophy leads to larger stroke volumes (larger chamber) in endurance athletes
- For every heartbeat, the heart muscles are passively extended (eccentric contraction)
- Eccentric hypertrophy leads to larger stroke volumes
Resistance/power athletes hearts
- Have more muscular walls
- If you contract the muscles, the heart will have to work against higher resistances
- Afterload is high, SV is low, and contractility is high
- The forces come together when the heart constricts
- Concentric hypertrophy and high afterload leads to lower stroke volume because the heart is constricted in resistance/power athletes