Lecture 25: Circulatory Response to Exercise

Question 1

What is the difference between dynamic and static exercise?

Answer 1

Dynamic exercise: muscle contraction that results in reduced joint angle and muscle shortening
Static exercise: muscle contraction that results in muscle shortening, with no joint angle changes

Question 2

What is the effect of increased dynamic exercise intensity on MAP?

Answer 2

Slight increase in mean arterial pressure

Question 3

Why does systolic blood pressure increase with exercise intensity?

Answer 3

Inotropic effect of heart: as exercise intensity increases, muscle contractions increase in force

Question 4

Why does diastolic blood pressure decrease with dynamic exercise intensity?

Answer 4

There’s a greater need for blood flow to muscles, therefore vasodilation occurs during diastole, which lowers TPR, causing a decrease in blood pressure

Question 5

What is the TPR - exercise intensity relationship?

Answer 5

TPR decreases with exercise intensity (curvelinear)

Question 6

How do we calculate TPR?

Answer 6

TPR= MAP/CO

Question 7

How can blood pressure response to exercise predict mortality?

Answer 7

Elevated BP response in the recovery stages of exercise increases mortality

Question 8

What is chronotropic incompetence and how does it affect mortality?

Answer 8

Where an individual can only reach 85% of their max heart rate during exercise due to excessive vasoconstriction
This increases mortality

Question 9

What are the three mechanisms that can increase stroke volume during exercise?

Answer 9

Increased filling of the heart during diastole (due to increased vasodilation via decreased TPR)
More forceful ejections of the heart (inotropic effect)
Greater EDV and lower ESV

Question 10

What is the Frank-Starling law?

Answer 10

The resting length of cardiac muscle determines force of contraction

Question 11

What is the effect of a greater EDV?

Answer 11

Greater filling during diastole, therefore stretching ventricle, leading to a more forceful contraction of blood

Question 12

What is cardiovascular drift?

Answer 12

The increase of heart rate and decrease in SV during prolonged aerobic exercise at a constant work rate

Question 13

What exaggerates the CV drift?

Answer 13

Heat stress

Question 14

How might excessive heat increase the cardiovascular drift?

Answer 14

Heat stress leads to sweating and therefore loss of blood plasma
This causes a decrease in venous return, leading to a requirement for heart rate to increase so as to maintain cardiac output

Question 15

Give a summary of the effects of increased dynamic exercise intensity on cardiovascular functions.

Answer 15

Increased HR (plateaus at top intensities)
Increased stroke volume (increases rapidly at exercise onset)
Decreased TPR
Slight increase in MAP (increase in systolic BP and slight decrease in diastolic BP)

Question 16

What is the effect of isometric contraction on blood pressure?

Answer 16

It increases blood pressure massively

Question 17

How does static exercise blood pressure changes differ to dynamic exercise?

Answer 17

Both diastolic and systolic blood pressure increase

Question 18

Why does diastolic pressure increase during static exercise?

Answer 18

Because there is elevated TPR in order to restrict muscle blood flow to unused muscles, therefore blood pumped to used muscles
This vasoconstriction is due to stimulation by the SNS

Question 19

How do isometric contractions affect afterload (amount of resistance heart has to eject against)?

Answer 19

They increase afterload due to increased firing by the SNS causing vasoconstriction

Question 20

What is the effect of increased afterload?

Answer 20

A greater inotropic effect (force of contractions needs to increase)

Question 21

How can weight training lead to dizziness/fainting?

Answer 21

Large vasoconstriction during high MVC
When contraction is finished, vasodilation increases rapidly to flush out metabolites
This causes a rapid decrease in CBF, causing fainting and dizziness

Question 22

Is there higher blood pressure in the arms or the legs during submaximal exercise?

Answer 22

Arms

Question 23

Why is there higher blood pressure in the arms during submaximal exercise?

Answer 23

Movement requires increased perfusion to other tissues (core muscles for stabilisation)
More vasoconstriction
Less venous return

Question 24

Why is snow-shovelling so fatal?

Answer 24

Increased vasoconstriction due to cold
Increased blood pressure as using the arms
Increased blood pressure as it is an isometric contraction

Question 25

Why do the arms have lower HR, O2 consumption and ventilation during maximal exercise?

Answer 25

Because they are a smaller amount of tissue therefore require less oxygen perfusion
Lower peripheral reflex input