VO2 Kinetics

Question 1

What is meant by O2 uptake kinetics?

Answer 1

• assessment of the rapidity that contracting skeletal muscles can adapt to using more or less oxygen in response to a change in metabolic demand, and the factors along the O2 utilization/transport route that might modulate the response

Question 2

Two techniques to estimate muscle O2 utilization

Answer 2

• VO2p (inhaled)
• VO2m (mitochondria)

Question 3

What is the difference between slow VO2 kinetics and fast VO2 kinetics?

Answer 3

• it takes longer for the person with slow VO2 uptake kinetics to reach a steady state of aerobic respiration (Oxidative phosphorylation)
• this results in a higher reliance on substrate level phosphorylation for ATP until steady state is reached
• this means increased Pi, ADP, La-, and H+, which all contribute to increased/quicker fatigue

Question 4

What factors determine VO2 kinetics (rate of adjustment for ox phos)?

Answer 4

• O2 supply to muscle fibres (delivery)
• Intracellular metabolic activation (utilization)

Question 5

4 parameters for Phase 2

Answer 5

Two VO2 parameters
- Baseline VO2
- VO2 amplitude - change in VO2 from baseline to the new steady state

Two time parameters
- TD - when the VO2 passes baseline
- T - time it takes for VO2 to reach 63% of VO2 steady-state

Question 6

On average, how much does O2 intake increase when the power is increased by 1W?

Answer 6

For healthy individuals - 10mL/min

Question 7

In relatively healthy individuals, how long does it take to reach T?

Answer 7

25-30 seconds

Question 8

What does the VO2 gain (G) represent?

Answer 8

The increase in the rate of O2 when the power is increased by 1W

• gives information about the efficiency of the individual’s oxidative metabolism (ie. how efficient their aerobic system is)

Question 9

What causes noise in our data and how do we reduce/ overcome it?

Answer 9

• noise due to irregularities in breathing patterns etc.
• performing multiple identical tests

Question 10

What are the three phases?

Answer 10

Phase 1 - Cardiodynamic phase
Phase 2 - Experimental phase
Phase 3 - VO2 steady-state

Question 11

When does VO2p = VO2m?

Answer 11

• after the cardiodynamic phase

Question 12

Why is there no a-VO2 difference at the caridodynamic phase?

Answer 12

• although the work rate has increased, the blood has not yet returned back to the heart, meaning that you can’t see the new difference between arterial blood and venous blood

Question 13

What does an increase in a-VO2 mean?

Answer 13

• increased VO2

Question 14

Will VO2p actually equal VO2m?

Answer 14

No, because VO2m is only measuring one muscle

Question 15

After how long will an individual reach steady-state?

Answer 15

• around 3 or 4T
  ex) if T = 20 seconds, then MSSVO2 will be reached in approx. 60-80 seconds

Question 16

Whats the equation for functional VO2 gain?

Answer 16

Change in VO2 steady state / Change in power output
in ml / min

Question 17

What are the implications of Chronic Heart Failure?

Answer 17

• inability of heart to pump properly
• can’t increase stroke volume
• therefore can’t increase Q that way
• Slower VO2 kinetics, as body has to rely more on increasing heart rate for increasing blood flow

Question 18

Factors affecting O2p delivery

Answer 18

• pulmonary ventilation
• arterial oxygenation
• Hb concentration
• cardiac output (Q)
• muscle blood flow
• distribution of blood flow
• muscle capillarity
• PO2 gradient

They all have to do with either the amount of oxygen in the blood, or the amount of blood being delivered to the place it needs to be

Question 19

Factors affecting O2 utilization

Answer 19

• mitochondrial density
• oxidative enzyme activity
• metabolic substrate supply

Question 20

True/False - the rate at which O2p adjusts to a new level is dependent of both bulk flow (convective) and concentration-driven (diffusive) oxygen transport processes.

Answer 20

False

the rate at which O2p adjusts to a new level is independent of connective and diffusive O2 transport processes

Question 21

Is it possible to improve an individual’s VO2 kinetics?

Answer 21

Yes
- study showed that after three weeks of training (3 times a week, 75% of VO2 max, 30-40 mins), older people were able to bring their T down to the starting volumes of the young group

Question 22

Is priming an effective tool for improving VO2 uptake kinetics?

Answer 22

Yes and no
- only worked for older adults
- they are limited by O2 delivery, so by doing a bit of heavy intensity exercise before lowering the intensity to moderate level exercise, their blood vessels are opened up and their O2 delivery is improved

Question 23

Is moderate or heavy intensity preferred when testing and measuring VO2 uptake kinetics?

Answer 23

• moderate intensity is preferred as steady state is reached in 2-3 mins, wheres above the lactate threshold, the third phase is delayed (takes longer to reach steady state above LT)