Lecture 21 - Physiological Adaptations to Exercise Training

Question 1

what are the determinants of VO2max?

Answer 1

• max cardiac output x max O2 extraction

Question 2

what is the relationship between VO2max and cardiac output (Q)?

Answer 2

• tight linear relationship
• mostly caused by SV changes which increase Qmax
• HR does not change much with training (may even decrease)

Question 3

how does training improve SV: preload?

Answer 3

• preload = the volume of blood received by the heart during diastole (EDV)
• training must increase preload to increase stroke volume

Question 4

How do blood volume changes affect VO2max?

Answer 4

• increase in BV due to an increase in PV (plasma volume)
• there is more circulating blood which means more blood can be accepted at the heart in the ventricles (therefore increasing SV)
• VO2 max is increased when SV is increased –> therefore VO2 max is improved with just increased circulation

Question 5

How does training improve SV: cardiac muscle?

Answer 5

• inotropic effect/contractility/how forceful contractions are influences how much blood flows from the heart
• influenced by 2 measurements

Question 6

what 2 measurements of the heart muscle influence stroke volume?

Answer 6

• myocardium thickness and left ventricle diameter

Question 7

how do myocardium thickness and left ventricle diameter affect stroke volume?

Answer 7

• larger diameter = accepts more blood in diastole = increases stroke volume
• thicker myocardium = stronger = more forceful contractions = increased stroke volume

Question 8

how does exercise training remodel the heart?

Answer 8

• stronger
• accepts more blood in diastole
• generates greater SV
• higher max cardiac output
• higher VO2 max

Question 9

how does the SV of the LV and RV correlate?

Answer 9

• SV of the RV and the LV have to be the same

Question 10

how does having a bigger/stronger heart affect aerobic capacity/VO2 max?

Answer 10

• bigger/stronger heart = increased VO2max

Question 11

how does training improve SV: afterload?

Answer 11

• pressure the heart must generate to open the aortic valve
• decreased pressure (afterload) = increased SV (for a given diastolic volume)
• this is a feature of exercise training

Question 12

How does the red blood cell volume affect exercise training duration?

Answer 12

• EV has no change in the beginning
• eventually increases (after several weeks of exercise training)
• causes a large percentage change after ~21 days (during this time PV plateaus, so all BV changes are from EV)

Question 13

What is arteriol O2 content?

Answer 13

• the a in a-vo2 difference
• measures SaO2 saturation, Hb concentration and O2 partial pressure in PaO2
• an increase in red blood cells = increased VO2 max (due to an increase in arterial oxygen content, RBC can carry moe oxygen to the arteries)

Question 14

What is muscle blood flow?

Answer 14

• the total volume of blood flowing to exercising muscle
• measured by MAP (driving pressure) / TPR (total peripheral resistance to flow)

Question 15

how is TPR measured?

Answer 15

• n (viscosity) x L (length of vessel) / r^4 (vessel radius)
• r^4 is the most important/influential factor (most of the flow is determined by whether the vessels are constricted or dilated)
• increased dilation = decreased resistance = increased flow

Question 16

how does training reduce peripheral resistance?

Answer 16

reduced by:
- arterial remodelling
- improved arterial function
*this facilitates greater muscle blood flow

Question 17

what is arterial remodelling?

Answer 17

• reducing vessel wall thickness and increasing vessel diameter to increase arterial flow
• this is caused by exercise training

Question 18

what is flow-mediated dilation?

Answer 18

• endothelial responsiveness to shear stress (aka flow-mediated dilation, aka stress from the movement of blood into the wall)
• exercise leads to a greater dilation response
• vasodilation improves muscle blood flow
• there is an increased peak dilation in exercised athletes

Question 19

what is peripheral resistance during exercise?

Answer 19

• vasoconstrictive signals during exercise are reduced in trained individuals
• sympathetic output is decreased
• less vasoconstriction = lower total peripheral resistance (in trained individuals)

Question 20

what is capillarization?

Answer 20

• the growth of new capillaries
• this increases the gas exchange surface area –> so we can extract more oxygen (diffusive capacity is increased)

Question 21

what happens to the mitochondria in trained athletes?

Answer 21

• increased oxygen utilization because there are more mitochondria and the enzymes in mitochondria are better at extracting oxygen
• there are more mitochondria in athletes

Question 22

how does mitochondria affect VO2max?

Answer 22

• increase in mitochondria = increase in VO2max
• due to biogenesis (increased mitochondria)

Question 23

what are the two factors of biogensis?

Answer 23

• hypertrophy = increased size of mitochondria
• proliferation = increased number of mitochondria
• increased number x size = increased mitochondria volume density

Question 24

what are the effects of increased mitochondria on volume density?

Answer 24

• increase in mitochondria = higher maximal rate of activation of the enzymes in mitochondria
• increased training = increased activation
• enzymes are used for the ETC and krebs cycle