Physiology 3120 Lecture Notes - Lecture 48: Vo2 Max, Partial Pressure, Exercise Intensity
2 May 2018
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Human Physiology Lecture 48
VO2 and VO2 max & Acid/Base balance
- Respiratory system is the primary site utilized to determine oxygen consumption
o Cardiovascular and respiratory system are involved too
VO2 + VO2 max
- Definition VO2: volume of oxygen that the body utilizes (while breathing room air)
o Sitting at rest, you are taking in oxygen – used by the heart, brain
- Definition VO2max: Maximum volume of oxygen that the body can utilize (while breathing room air)
o While you start exercising
o Beast measure of aerobic fitness
- Units: Liters/min or ml/kg/min
- Average person: 30-40ml/kg/min
- VO2 Max is a good (the best) measure of aerobic fitness
o Ex. Cyclist and cross country skiers have high VO2 max
VO2 max, VO2 max, VO2 max
- Factors influencing VMAX
o IMPORTANT FOR TRAINING TO INCREASE VO2 MAX:
▪ 1) Cardiovascular system get the oxygen there
• If you want to train to increase your VO2, it is about getting oxygen to your
muscles, and getting cardiovascular system to get the oxygen there
▪ 2) Muscles oxygen utilization
o IMPORTANT FOR MEASUREMENT OF VO2MAX
▪ 3) Respiratory system get the oxygen in the blood
• And removing the carbon dioxide
• NOT a limiting factor
How can it be measured?
- Definition: Maximum volume of oxygen that the body can utilize (while breathing room air)
- Measurement VO2: Amount of oxygen inhaled - amount of oxygen exhaled
o To determine the amount of oxygen the body utilizes
- VO2 = (Minute volume * % O2 of inhaled air) – (minute volume * %O2 exhaled air)
- Remember: Minute volume = tidal volume * respiratory rate
o How much air goes into and out of your lungs in a minute
Measurement of max: Stepwise increases in workload on a treadmill for example.
- For VO2max, it is determined by the combined function of cardio, musculoskeletal and respiratory
system
- Subject performs an aerobic exercise while VO2 measured
- the intensity increases in a step-wise fashion
o Measure the VO2max
find more resources at oneclass.com
find more resources at oneclass.com
o Measuring the oxygen that is exhaled, tidal volume with spirometer
▪ Ask person to increase their intensity step wise
o Ex. On treadmill, cycle
o NOTE: the exercise has to utilize major muscle groups
▪ Can reach your maximum VO2 without it
- When you measure the VO2 – the VO2 increases linearly until you reach a point where even if you
increase the intensity, your VO2 consumption does not change
o You have reached your VO2 maximum
- Initially, each stepwise intensity increase will lead to an increase in VO2
o When an exercise level is reached where the body cant consume more oxygen, VO2 no
longer increases with increase exercise intensity = VO2MAX
- VO2 measuring the amount of oxygen inhaled minus exhaled
Oxygen Transport
- Inhale the air, it gets through the alveolar surface, diffuses into the blood
o Oxygen transported into the blood
- OXYGEN IS TRANSPORTED TWO DIFFERENT WAYS
1. Dissolved gas
2. Bound to hemoglobin (MAJORITY)
Oxygen transport: as a dissolved gas
- Minor component of O2 transport!!
- (enry’s Law: concentration of dissolved gas = pressure * solubility
o O2 not very soluble in blood
- Only approx. 0.3ml of O2 per 100 ml blood is transported this way!!!
o Transport less than a ml of oxygen per 100 ml of blood as a dissolved gas NO WHERE
NEAR THE AMOUNT WE NEED
- Not adequate to meet tissue demands!!
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find more resources at oneclass.com
Oxygen transport: bound to hemoglobin
- Major component of O2 transport!!
- Hemoglobin is a protein consisting of 4 subunits
o Each subunit binds to one oxygen
- Each subunit contains a heme moiety to which one O2 molecule can bind
o Oxygen binds to the heme subunit and it can be transported that way
o Therefore, each Hb can bind 4 oxygen molecules
- One gram of hemoglobin can hold a maximum of 1.34ml O2
o This maximum is reached at a high Po2 (760 mmHg), 100% Hb saturation
- In blood there is approximately 15g Hb/100ml
o A lot of hemoglobin in the blood!
o This means that 100ml of blood could hold a maximum of 20.1 mL oxygen bound to
hemoglobin
How much oxygen does the blood hold?
EXPERIMENT:
- Take a little bit of blood and divide it into different containers and expose them to different partial
pressures of oxygen
- Once you get to equilibrium you can measure how much oxygen is in the blood, how much is
dissolved, how much is bound to hemoglobin
- Result: oxygen-hemoglobin dissociation curve
Oxygen-hemoglobin dissociation curve
- Left Vertical axis: hemoglobin saturation
o How much of the hemoglobin is bound to oxygen
- Right Vertical axis: oxygen content in ml/100ml
- Horizontal axis: partial pressure of oxygen
- Line is the amount of oxygen that is bound to hemoglobin
- Dashed line is the dissolved oxygen
- Total oxygen = dissolved oxygen + oxygen bound to hemoglobin
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Respiratory system is the primary site utilized to determine oxygen consumption: cardiovascular and respiratory system are involved too. Definition vo2: volume of oxygen that the body utilizes (while breathing room air: sitting at rest, you are taking in oxygen used by the heart, brain. Definition vo2max: maximum volume of oxygen that the body can utilize (while breathing room air: while you start exercising, beast measure of aerobic fitness. Vo2 max is a good (the best) measure of aerobic fitness: ex. Cyclist and cross country skiers have high vo2 max. Important for training to increase vo2 max: 1) cardiovascular system (cid:498)get the oxygen there(cid:499, 2) muscles (cid:498)oxygen utilization(cid:499, 3) respiratory system (cid:498)get the oxygen in the blood(cid:499, and removing the carbon dioxide, not a limiting factor. If you want to train to increase your vo2, it is about getting oxygen to your muscles, and getting cardiovascular system to get the oxygen there.
