Week 8 - Response to exercise Flashcards
(36 cards)
What is a normal resting HR range for trained an untrained populations?
What affects resting HR?
60-80bpm for untrained and as low as 30-40bpm in trained.
Neural tone, temperature and altitude.
What is the resting HR screening cut off?
90bpm.
If higher may be sleep deprived or fighting infection.
What is the anticipatory rise response?
An increase in HR above resting just before the start of exercise as a result of decreased vagal tone.
How does HR change during exercise?
It increases in direct proportion to exercise intensity.
Maximum HR is achieved in an all out effort - to be a max it should be highly reproducible and decline with age.
What is steady state HR?
A point of plateau.
The optimal HR for meeting circulatory demands at a given submaximal intensity.
A plateau suggests it is steady state if submaximal, if no plateau not steady state.
If exercise intensity increases, so does steady state HR.
Adjustment to a new intensity takes 2-3 minutes.
At what point does SV stop increasing during exercise?
40-60% VO2max.
Plateaus beyond this point until exhaustion.
This is not always the case - in elite endurance athletes SV can continue increasing upwards of 80% VO2max.
By how much does SV increase in maximal exercise?
Roughly double standing SV - 2x SV at rest.
Only slightly different during maximal exercise than supine SV - laying down.
Supine EDV>standing EDV due to venous return and skeletal muscle pump. There is a lower volume of blood in the left and right ventricles after filling phase when standing.
How does cardiac output change in elite and non-elite during exercise?
Increases due to increases in SV and HR.
Steeper increase in elite as they can increase their SV by a greater amount - increase does not plateau as in non-elite.
What are the three factors that increase SV during exercise?
Preload
Contractility
Afterload
How does preload affect SV?
Increases stretch –> increased end diastolic volume (volume of blood in ventricle before it contracts) –> increases contraction strength –> frank-Stirling mechanism.
How does contractility affect SV?
Increased noradrenaline or adrenaline increases contractility. This is independent of EDV (increased ejection fraction instead - percentage of blood in the ventricle that leaves on contraction).
How does afterload affect SV?
Afterload is the pressure the heart must work at to eject the blood.
It decreases due to reduced aortic resistance in trained and elite individuals. (Increases SV).
How much of cardiac output is redirected to muscles during maximal intensity exercise?
80%
What are the normal values of cardiac output?
Resting, untrained exercise and trained exercise.
5L
20L
40L
What is the Fick equation?
VO2 (oxygen consumption) = Cardiac output x (a-v O2 differece)
What does the Fick equation show oxygen consumption depends on?
Blood flow (Q) and O2 extraction - this is an adaptation in elite individuals.
Haemoglobin change shape when oxygen is removed – oxygen has a high affinity for haemoglobin but a higher affinity for myoglobin in the muscles. Hence elite trained athletes have more myoglobin to snatch the oxygen from the haemoglobin.
How does blood pressure change during endurance exercise?
Mean arterial pressure increases (average of systolic and diastolic blood pressure).
Systolic blood pressure increases
Diastolic blood pressure slightly decreases (increases at max exercise). Main change is systolic blood pressure.
What is the equation for mean arterial pressure?
How is it affected during exercise?
Cardiac output (Q) x total peripheral resistance (TPR)
Q increases
TPR decreases due to vasodilation.
Blood flow redistribution
Blood flow is redistributed towards the active working muscles (greatest metabolic need).
Sympathetic vasoconstriction decreases blood flow away from less active regions (spanchnic circulation - liver, pancreas, GI and kidneys).
Effect of vasodilation during exercise
Local vasodilation permits additional blood flow in exercising muscle - triggered by metabolic endothelial products e.g. lactate.
As temperature rises skin VD allows heat loss through the skin.
What is cardiovascular drift?
What is it caused by?
HR continues to increase during exercise despite a decrease in SV, to maintain Q.
Associated with an increased core temperature and dehydration.
Mainly caused by a decrease in venous return.
What can affect blood flow redistribution?
Temperature - may force blood towards to skin to reduce core temperature (moves away from the muscles).
Hence marathons are ran in the morning as lowest circadian temperature.
How does ventilation change during exercise?
Immediate increase before muscle contractions - anticipatory response.
Second gradual increase in ventilation - driven by chemical changes in arterial blood (increased CO2 and H+ sensed by chemoreceptors)
increase is proportional to metabolic needs of muscle.
At low intensities only tidal volume increases but then rate as intensity increases.
What is dyspnea?
What causes it?
Shortness of breath
Poor aerobic fitness, intensive training, unfamiliar workloads.
Inability to adjust to high blood PCO2 and H+.
