CV Response to Exercise

Question 1

Why does the CV system adapt to exercise? (acutely and chronically)

Answer 1

Acutely - to increase oxygen delivery to working muscles by increasing blood flow to muscles and reducing delivery to low activity tissues.

Chronically - to deliver more oxygen to active muscle mass. More effective oxygen delivery during sub-maximal exercise and increased maximum oxygen consumption (Vos max)

Question 2

What CV factors influence oxygen uptake and VO2 max?

Answer 2

Cardiac structure and function
Blood (plasma) volume
Blood flow and distribution
Oxygen extraction (arterio-venous difference)

Question 3

How does training increase sub-maximal and maximal oxygen values in muscle?

Answer 3

Active muscle can utilise oxygen more efficiently by increasing oxidative capacity (eg higher oxidative enzyme content)

Question 4

What is preload?

Answer 4

The amount of blood in the ventricle before contraction.

Question 5

What does preload determine?

Answer 5

Cardiac muscle length before contraction

Question 6

What is the most important determining factor for preload?

Answer 6

Venous return

Question 7

What is afterload?

Answer 7

The pressure against which the ventricle must contract (vascular resistance). The higher the afterload, the less blood will be ejected per heartbeat

Question 8

The Frank-Starling Mechanism

Answer 8

Based on the length-tension relationship within the ventricle - the greater the stretch, the greater the contraction.
If preload is increased, the ventricular fibre length is also increased, resulting in an increased tension of the muscle

Question 9

Left ventricle in endurance athletes

Answer 9

Left ventricular volume is larger.
Greater preload - greater stroke volume - eccentric hypertrophy

Question 10

Left ventricle in resistance athletes

Answer 10

Posterior wall thickness and septal thickness larger
Greater afterload - lower stroke volume - concentric hypertrophy

Question 11

What is stroke volume determined by?

Answer 11

Preload
Afterload
Contractability

Question 12

What is cardiac output related to?

Answer 12

Venous return
Vascular resistance
Smoking, or an unhealthy diet, can increase vascular resistance (‘stiff vessels’)

Question 13

Stroke volume adaptations in endurance athletes

Answer 13

Greater preload - greater ventricular dimensions
Greater diastolic filling time due to bradycardia (slow heart rate)
Greater contractability
Greater maximal stroke volume

Question 14

Heart rate adaptations in endurance athletes

Answer 14

Greater stroke volume - lower HR for the same cardiac output (sub-maximal exercise)
Note: Different HR at the same intensity
Maximal HR unchanged

Question 15

Cardiac output adaptations for endurance athletes

Answer 15

Most significant adaptation - VO2 max
Training adaptation at sub-maximal exercise

Question 16

What is acute blood flow regulation?

Answer 16

The muscle metabolites
Dilator substances produced by the endothelium (eg nitric acid)
Pressure changes within the vessel
Sympathetic activity - reduced blood flow to low activity tissues (reduced urine output and increased water retention)

Question 17

Blood volume changes

Answer 17

Cross sectional - higher blood volume in trained athletes
Longitudinal - increased plasma volume (10 days) then red blood cells increase (months) - haemoglobin concentration and the haematocrit remain the same but absolute plasma volume and red blood cell number increase.

Question 18

Blood doping scandal 2019

Answer 18

Erythroprotein (EPO) induces the production of RBCs
Blood transfusions: with own blood=autologous. With another’s blood=homologous