VO2

What limits our ability to do aerobic exercise?

O2 delivery to muscles and how well the muscles utilize O2.

Immediate energy system

First system used, fully depleted after ~30 seconds.

Short-term energy system

Kicks in after around 15 seconds, lasts for about 2 minutes.

Long-term energy system

Main source of energy after around the 2-minute mark.

What is VO2?

VO2 is oxygen consumption, the amount of O2 taken up, transported, and used at the cellular level.

VO2max

Maximal oxygen consumption, indicates an individual’s capacity to re-synthesize ATP aerobically.

Why do we care about VO2max?

It is an excellent measure of overall fitness, accurately prescribes exercise, and is a clinical marker of mortality risk.

Fick Principle

The principle stating the amount of substrate that goes into an organ minus the amount that comes out equals that tissue's utilization rate of that substrate.

Absolute vs Relative VO2

Absolute VO2 is measured in liters per minute, relative VO2 is expressed relative to body weight.

What is the difference between VO2max and VO2peak?

VO2max is the maximum oxygen uptake during increasing exercise intensity; VO2peak is the highest uptake reached during a test.

Continuous VO2max protocol

No rest between exercise increments, usually lasts 7-12 minutes.

Discontinuous VO2max protocol

Several minutes rest between stages, allows feedback from the subject.

Main factors affecting maximal oxygen uptake

Exercise mode, genetics, training state, biological sex, body composition, and age.

Verification test for VO2max

Complete a short verification phase at a 10% higher work rate to ensure VO2 does not rise any further.

Graded sub-max exercise

Used to predict VO2max by measuring heart rate and VO2.

What limits our ability to do aerobic exercise?

O2 delivery to muscles and how well the muscles utilize O2.

Immediate energy system

First system used, fully depleted after ~30 seconds.

Short-term energy system

Kicks in after around 15 seconds, lasts for about 2 minutes.

Long-term energy system

Main source of energy after around the 2-minute mark.

What is VO2?

VO2 is oxygen consumption, the amount of O2 taken up, transported, and used at the cellular level.

VO2max

Maximal oxygen consumption, indicates an individual’s capacity to re-synthesize ATP aerobically.

Why do we care about VO2max?

It is an excellent measure of overall fitness, accurately prescribes exercise, and is a clinical marker of mortality risk.

Fick Principle

The principle stating the amount of substrate that goes into an organ minus the amount that comes out equals that tissue's utilization rate of that substrate.

Absolute vs Relative VO2

Absolute VO2 is measured in liters per minute, relative VO2 is expressed relative to body weight.

What is the difference between VO2max and VO2peak?

VO2max is the maximum oxygen uptake during increasing exercise intensity; VO2peak is the highest uptake reached during a test.

Continuous VO2max protocol

No rest between exercise increments, usually lasts 7-12 minutes.

Discontinuous VO2max protocol

Several minutes rest between stages, allows feedback from the subject.

Main factors affecting maximal oxygen uptake

Exercise mode, genetics, training state, biological sex, body composition, and age.

Verification test for VO2max

Complete a short verification phase at a 10% higher work rate to ensure VO2 does not rise any further.

Graded sub-max exercise

Used to predict VO2max by measuring heart rate and VO2.

Fick Equation for VO2

VO2 = $Q$ x $(a-vO<em>2)$ difference, where $Q$ is cardiac output and $(a-vO</em>2)$ is the arterial-venous oxygen difference.

What is Cardiac Output ($Q$)?

The amount of blood pumped by the heart per minute, calculated as heart rate x stroke volume (HR x SV).

What is the $(a-vO_2)$ difference?

The difference in oxygen content between the arterial blood and the venous blood, representing the amount of oxygen extracted by the tissues.

Criteria for reaching VO2max

1. A plateau in VO2 (increase of <$2$mL/kg/min with increased workload).
2. Respiratory Exchange Ratio (RER) >$1.1$.
3. Heart Rate (HR) within $10$ bpm of predicted maximum.
4. Blood lactate >$8$mmol/L.
5. Rating of Perceived Exertion (RPE) >$17$ (on a 6-20 scale).