Exercise Physiology

Question 1

What is dynamic exercise?

Answer 1

This is a rhythmical movement of joints alongside the contraction and relaxation of muscles such as in swimming, running and cycling

Question 2

What is static exercise?

Answer 2

This is where there is maintained muscular contraction for a length of time e.g. weight lifting

Question 3

What is the immediate energy supply to the skeletal muscle?

Answer 3

Phosphocreatine; this provides a store of high-potential phosphate which can be cleaved by creatine kinase to allow the phosphate to bind to ADP to produce ATP for energy metabolism

Question 4

What is the energy supply to the skeletal muscle during sprinting?

Answer 4

ATP is generated from glucose via the glycolytic pathway and leads to the production of pyruvate and subsequently lactate. This lactic acid build up leads to a drop in pH and the muscle begins to fatigue relatively quickly.

Question 5

What is the energy supply to the skeletal muscle during aerobic exercise?

Answer 5

In this process there is a sustained supply of ATP and the use of oxygen as oxidative phosphorylation takes place.

Question 6

What is meant by VO2 max?

Answer 6

The maximum volume an individual can take up/use during dynamic exercise, and therefore this is indicative of an individual’s aerobic/endurance fitness

Question 7

How is VO2 max affected by COPD or advanced heart disease?

Answer 7

These factors reduce VO2 max

Question 8

How is VO2 max affected by physical training?

Answer 8

Increases VO@ max

Question 9

What is meant by an individual’s lactate/anaerobic threshold?

Answer 9

The lactate threshold is the point as which lactic acid begins to accumulate in the bloodstream; untrained individuals will have a low anaerobic threshold whereas elite endurance athletes will have a high anaerobic threshold.

Question 10

How does the cardiovascular system respond to exercise?

Answer 10

Increased activation of sympathetic nerves to increase heart rate (B1 adrenoreceptors) and cause vasoconstriction (a1 adrenoreceptors) to increase mobilisation of blood from the great veins to increase venous return, and hence preload which leads to a greater contraction and therefore also increases stroke volume. In addition, b2 receptors in the lungs are activated to relax bronchial smooth muscle and increase ventilation.

Question 11

Outline the function of alpha adrenoreceptors in the exercise response

Answer 11

Sympathetic innervation leads to noradrenaline release which causes stimulation of the alpha 1 adrenoreceptors on the smooth muscle of vessels in the gut and veins to cause vasoconstriction that increases venous return to the heart –> increased preload –> increase cardiac contractility (Starling’s mechanism) –> greater stroke volume

Question 12

Outline the function of beta 1 adrenoreceptors in the exercise response

Answer 12

Beta 1 adrenoreceptors are found in the heart, and when NA is released from the sympathetic axons it causes positive inotropic and chronotropic effects to increase HR and contractility which increases cardiac output

Question 13

Outline the function of beta 2 adrenoreceptors in the exercise response

Answer 13

Beta 2 adrenoreceptors are found in the smooth muscle of the airways and NA release from sympathetic axons leads to the relaxation of this smooth muscle which increases bronchial diameter and therefore increases perfusion, as well as functioning to increase ventilation rate.

Question 14

How is blood shunted towards the exercising muscle and away from inactive systems during exercise?

Answer 14

Systemic vasoconstriction as a result of alpha 1 adrenoreceptor action can be overridden by active muscle due to the release of powerful local vasodilator release (e.g. nitric oxide and adenosine)

Question 15

How does blood pressure change during exercise?

Answer 15

Increases due to increased cardiac contractility and systemic vascular resistance increase (due to systemic vasoconstriction))

Question 16

How does mean arterial pressure change during exercise?

Answer 16

Only rises slightly due to the decrease in total peripheral resistance being compensated for by the increase in cardiac output

Question 17

Why do elite athletes have low heart rate?

Answer 17

There is increased venous return to the heart during the exercise and therefore this causes volume-induced cardiac hypertrophy in athletes which increases resting end diastolic volume, and therefore increases stroke volume, meaning that more blood can be pumped in each beat, so the heart rate decreases.

Question 18

How does haemoglobin’s affinity to oxygen change during exercise?

Answer 18

During exercise there is increased pCO2 of venous blood, increased H+ levels (due to lactate production in anaerobic respiration) and an increase in the local and tissue temperature and this reduces haemoglobin’s affinity for oxygen and therefore it can dissociate more readily and diffuse into the actively metabolising tissues to supply respiration.

Question 19

What is meant by ‘oxygen debt’

Answer 19

Oxygen consumption doesn’t rise quickly enough to meet the energy requirements immediately, and this initial ventilation lag forms an oxygen debt that must be repaid at the end of the exercise period

Question 20

What metabolic activities occur during oxygen debt repayment

Answer 20

ATP and phosphocreatine are re-synthesised via oxidative pathways, and then lactate is converted to re-form glucose and glycogen

Question 21

Outline the role of the nervous system in coordinating ventilation to exercise demands

Answer 21

Autonomic factors:

Parasympathetic inhibitions and sympathetic stimulation

Question 22

What is meant by the ‘central command’

Answer 22

A higher brain level that acts to modulate the baroreceptor sensitivity during exercise in order to allow an increase in blood pressure

Question 23

How does exercise affect cellular oxygen uptake?

Answer 23

At high levels of exercise, pO2 of blood decreases slightly whilst the pCO2 in the mixed venous blood rises and therefore the arteriovenous difference creates a larger gradient to drive oxygen-dissociation into the tissues