Lecture 21 - Physiological Adaptations to Exercise Training Flashcards
what are the determinants of VO2max?
- max cardiac output x max O2 extraction
what is the relationship between VO2max and cardiac output (Q)?
- tight linear relationship
- mostly caused by SV changes which increase Qmax
- HR does not change much with training (may even decrease)
how does training improve SV: preload?
- preload = the volume of blood received by the heart during diastole (EDV)
- training must increase preload to increase stroke volume
How do blood volume changes affect VO2max?
- 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
How does training improve SV: cardiac muscle?
- inotropic effect/contractility/how forceful contractions are influences how much blood flows from the heart
- influenced by 2 measurements
what 2 measurements of the heart muscle influence stroke volume?
- myocardium thickness and left ventricle diameter
how do myocardium thickness and left ventricle diameter affect stroke volume?
- larger diameter = accepts more blood in diastole = increases stroke volume
- thicker myocardium = stronger = more forceful contractions = increased stroke volume
how does exercise training remodel the heart?
- stronger
- accepts more blood in diastole
- generates greater SV
- higher max cardiac output
- higher VO2 max
how does the SV of the LV and RV correlate?
- SV of the RV and the LV have to be the same
how does having a bigger/stronger heart affect aerobic capacity/VO2 max?
- bigger/stronger heart = increased VO2max
how does training improve SV: afterload?
- 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
How does the red blood cell volume affect exercise training duration?
- 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)
What is arteriol O2 content?
- 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)
What is muscle blood flow?
- the total volume of blood flowing to exercising muscle
- measured by MAP (driving pressure) / TPR (total peripheral resistance to flow)
how is TPR measured?
- 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
how does training reduce peripheral resistance?
reduced by:
- arterial remodelling
- improved arterial function
*this facilitates greater muscle blood flow
what is arterial remodelling?
- reducing vessel wall thickness and increasing vessel diameter to increase arterial flow
- this is caused by exercise training
what is flow-mediated dilation?
- 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
what is peripheral resistance during exercise?
- vasoconstrictive signals during exercise are reduced in trained individuals
- sympathetic output is decreased
- less vasoconstriction = lower total peripheral resistance (in trained individuals)
what is capillarization?
- the growth of new capillaries
- this increases the gas exchange surface area –> so we can extract more oxygen (diffusive capacity is increased)
what happens to the mitochondria in trained athletes?
- increased oxygen utilization because there are more mitochondria and the enzymes in mitochondria are better at extracting oxygen
- there are more mitochondria in athletes
how does mitochondria affect VO2max?
- increase in mitochondria = increase in VO2max
- due to biogenesis (increased mitochondria)
what are the two factors of biogensis?
- hypertrophy = increased size of mitochondria
- proliferation = increased number of mitochondria
- increased number x size = increased mitochondria volume density
what are the effects of increased mitochondria on volume density?
- 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
