Physiology 3120 Lecture Notes - Lecture 47: Vo2 Max, Spirometry, Respiratory System
15 May 2018
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Lecture 27 – VO2 Max and CO2 Max
VO2, VO2 max
- Definition VO2: volume of oxygen that the body utilizes (while breathing room air)
- Definition VO2max: maximum volume of oxygen that the body can utilize (while breathing
room air) → when exercising
o Best measures of aerobic fitness
- Units: Liters/min or ml/kg/min (for body weight)
- Average person: 30-40ml/kg/min (higher in elite athletes)
- VO2 max is a good (the best) measure of aerobic fitness (cycling, skiing, marathon running)
VO2 max
- If you want to train to increase VO2, it is about getting oxygen to muscles and getting
cardiovascular system to get the oxygen there
- Training people do to improve VO2 max is related to cardiovascular and muscles
- Respiratory system is good at getting oxygen in blood and removing CO2 → not a limiting
factor
- Respiratory system and spirometry is used to help measure VO2/VO2 max
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How it can 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 This is how much O2 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 in and out of the lungs in a minute
Measurement of max: stepwise increases in workload on a treadmill for example
- To get VO2 max, get a person to do an exercise where the intensity increases in a step wise
fashion and VO2 is measured
o Measure oxygen that is exhaled, the tidal volume by a spirometry method
o Exercise must utilize major muscle groups in order to reach VO2 max
- Stepwise increase:
o VO2 increases linearly until you reach a point where even if you increase intensity,
VO2 does not change = the max!
OXYGEN TRANSPORT:
1. Dissolved gas in blood
2. Bound to hemoglobin (majority)
- Inhale air, gets to alveolus surface, diffuses into blood, transported in the blood
Oxygen transport: as a dissolved gas
- Minor component of O2 transport!!
- (enry’s Law: concentration of dissolved gas = pressure * solubility
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- O2 not very soluble in blood
- Only approx. 0.3ml of O2 per 100 ml blood is transported this way as a dissolved gas!!
- Not adequate to meet tissue demands!!!!
o VO2 levels were of 30-40 L/min an 0.3 mL is not enough
Oxygen transport: bound to hemoglobin
- Major component of O2 transport!!
- Hemoglobin is a protein consisting of 4 subunits
- Each subunit contains a heme moiety to which one O2 molecule can bind
- Oxygen binds to a heme subunit to transport oxygen
- One gram of hemoglobin can hold a maximum of 1.34 mL O2
- In blood there is approximately 15g Hb/100ml
- We transport a lot of oxygen this way → a lot of molecule, each with 4 spots
Experiment – how much oxygen does blood hold?
- Take some blood and divide it into different containers and expose it to different partial
pressures of oxygen
- After equilibrium, measure how much oxygen is in the blood, bound to hemoglobin and
dissolved → result is the oxygen-Hb dissocation curve
Oxygen-hemoglobin dissociation curve
- Hb saturation: how much Hb is bound to oxygen
- Total O2: dissolved O2 + O2 bound to Hb
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 27 vo2 max and co2 max. Definition vo2: volume of oxygen that the body utilizes (while breathing room air) Definition vo2max: maximum volume of oxygen that the body can utilize (while breathing room air) when exercising: best measures of aerobic fitness. Units: liters/min or ml/kg/min (for body weight) Average person: 30-40ml/kg/min (higher in elite athletes) Vo2 max is a good (the best) measure of aerobic fitness (cycling, skiing, marathon running) If you want to train to increase vo2, it is about getting oxygen to muscles and getting cardiovascular system to get the oxygen there. Training people do to improve vo2 max is related to cardiovascular and muscles. Respiratory system is good at getting oxygen in blood and removing co2 not a limiting factor. Respiratory system and spirometry is used to help measure vo2/vo2 max. Definition: maximum volume of oxygen that the body can utilize (while breathing room air)
