Exercise Physiology

Question 1

What is the relationship between oxygen consumption and exercise intensity?

Answer 1

Oxygen uptake is exercise dependent - increasing as the intensity of physical activity elevates

There is a maximal level of O2 uptake where increases in intensity aren’t matched by O2 uptake due to the maximal ability of the body to supply and use O2

Question 2

What is the VO₂?

Answer 2

VO2 is the rate of O2 consumption at any point in time

VO2 Max is the maximal level of O2 consumption within an individual

VO2= Q x (CaO2 - CvO2)

VO2 increases as the body increases O2 supply to skeletal and cardiac muscle during exercise

Question 3

Describe the concept of hyperaemia

Answer 3

Hyperaemia is the increase in muscle blood flow in exercise

Metabolic vasodilators from contracting skeletal muscle, endothelium and RBC’s result in increased blood blow to active muscles

Because of this, muscle becomes the predominant site of cardiac outout supply

Other factors that may contribute to hyperaemia include: muscle pump mediated postural hypotension following exercise and functional sympatholysis due to ineffective Sympathetic NS

Question 4

What is the difference between an athlete and a sedentary individual in terms of their cardiac output?

Answer 4

Cardiac output of these populations can be the same but are achieved in different ways

Athletes with training have lower HR with higher SV (due to larger LVEDV and blood volume)

Sedentary people rely more heavily on HR to meet CO

Question 5

How does a persons MAP, diastolic and systolic blood pressure change with exercise intensity?

Answer 5

Diastolic BP remains relatively constant/slightly decreases across all levels of exercise intensity

Systolic BP sharply elevates in response to increases in cardiac output

Mean Arterial Pressure (MAP) increases due to the greater change in systolic BP and that diastole phase is reduced with increased HR

Question 6

What is cardiovascular drift?

Answer 6

Cardiovascular drift is the phenomenon where some cardiovascular responses begin a time dependent change, or “drift” after around 10 minutes of exercise in a warm or neutral environment without an increase in workload.

It is characterised by:

• Increase in HR
• Increase in TPR
• Decrease in blood volume
• Decrease in MAP
• Decreased SV
• Decreased CO

Question 7

What factors are considered to be responsible for causing cardiovascular drift in prolonged exercise?

Answer 7

Increased HR + decreased SV due to exercise

Hyperthermia

Dehydration

Increased plasma adrenaline concentrations

Peripheral displacement of blood volume due cutaneous vasodilation

Question 8

Outline the changes in autonomic control of cardiac output during exercise

Answer 8

Parasympathetic vagus nerves and sympathetic nerves supply and modulate the heart

Vagus nerves are the dominant controller of HR at rest/light exercise

Sympathetic NS is the dominant controller of HR at high exercise intensity

Question 9

By what mechanisms is cardiac output increased following training in athletes?

Answer 9

Expanded blood volume (Frank-Starling curve)

Heart Hypertrophy (LV mass+ chamber size)

Increased adrenergic sensitivity (SA node may change intrinsic properties)

Increased capillary density

Increased capillary recruitment

Question 10

What is the role of the respiratory system in exercise?

Answer 10

The respiratory system:

**maintains arterial O2 saturation **

CO2 removal

Acid-base balance

Fluid and temperature balance

(more in animals than humans)

Question 11

What factors contribute to the control of ventilation in exercise?

Answer 11

Respiratory neurons in the medulla recieve input from a number of sources to regulate ventilation; including:

Chemoreceptors (CO2 + O2)

Pressure receptors

Mechanoreceptors

pH

Stretch receptors

Body temperature

Pain receptors

Question 12

What is exercise hyperpnea?

What contributes to it?

Answer 12

Exercise hyperpnea is the increase depth and rate of breath incurred in response to exercise

It arises as a result of signals to respiratory neurons from:

• Motor cortex
• Afferent nerves of working muscle
• CO2 flux to lungs
• Elevated catecholamines and temperature
• Increased lactate, H+ and K+

**NOTE: **Oxygen has no influence on regulating respiration in exercising individuals

Question 13

What ventilatory adaptations occur following training?

Answer 13

As a result of training, individuals can maintain an arterial O2 content at a reduce ventilatory effort

This is achieved by:

**Reduced blood lactate/H+ **

Lower plasma K+

Lower plasma catecholamines

Reduced central drive

Reduced muscle afferent effects

Question 14

What is considered to be the limiting factor of VO2?

Answer 14

VO2 is primarily determined by the body’s ability to deliver O2 to respiring tissues

Respiration, central circulation and peripheral circulation factors largely limit a person VO2

Metabolism of O2 is another limiting factor - but has less of an effect that the delivery mechanisms to active tissue

Question 15

What are the mechanisms of heat loss during exercise?

Answer 15

From most prominent to least prominent:

1. Sweat evaporation
2. Convection/Conduction
3. Radiation
4. Respiration heat loss

Question 16

What effect does heat stress have on exercise capacity an performance?

Answer 16

At higher temperatures, individuals have lower capacity to exercise (less period of exercise time) and have lowered performance (can’t achieve as higher intensity)

Precooling before exercise can improve capacity and performance

Question 17

What affect does dehydration have on exercise?

Answer 17

Dehydration reduces the capacity and performance of exercise.

This is true for dehydration incurred both during and prior to the onset of the exercise

The benefits of hydration include:

Increased blood volume

decreased HR

Increased SV and CO

Lower core temperature

Lower plamsa [Na+] and osmalality

Reduced muscle glycogen use

**Enhanced performace **