LisaS
06-09-2006, 11:55 PM
I was reading back in the June challenge section – and realized that I had somewhat “committed” to writing up something about VO2 max – so here it is. I'm kinda long winded ;)
Technically, I'll be talking about V-dot O2 max (written as http://jap.physiology.org/content/vol98/issue4/fulltext/1371/f1.gifO2 ) (but I'm too lazy to keep formatting it that way each time). The “dot” in V-dot indicates that we are talking about a rate and not an absolute value. V-dot O2 max refers to the maximum amount of O2 that a person can utilize in a period of time. It can either be expressed in absolute units like L O2 per minute, or in size adjusted units of ml O2/kg/min. The “dot” in V-dot indicates that we are talking about a rate and not an absolute value. But only physio texts call it V-dot or bother to write with the V and the little dot ahove – so I'll quit that and just call it VO2 max – but you remember what it means.
I'll reference some good physiology sites & articles discussion VO2 max at the end. Exercise Physiology is one of my favorite subjects.
You all remember that the endpoint of cellular respiration is the reduction of O2 to H2O while producing ATP. So, the amount of O2 that you can maximally consume (use up) is an indirect measure of how much energy you are able to produce at your max capacity. What can influence VO2? Well, let's look at the road that O2 travels to get to those cellular factories we call mitochondria. First, air (at 21% O2) has to enter your lungs and get down to your alveoli. Then the O2 has to diffuse across the alveoli and get picked up by the hemoglobin (Hb) in red blood cells (RBC). Each Hb molecule can bind up to 4 O2 molecules. Hb has iron as a main component.
Your now oxygenated blood goes from the lungs to the left side of the heart, where it is squirted out into your aorta and on to the rest of the cells in your body. Once it finds a target tissue (like skeletal muscle) and the blood is in the capillary bed, the Hb releases the O2 which again has to diffuse to its destination – your cell. The O2 makes its way to the mitochondria in the cell where it can act as the final electron receptor and be reduced to water – as you are making ATP . The now deoxygenated blood flows back through the venous system (carrying CO2) and enters the right side of the heart. The heart pumps this deoxygenated blood to the lungs, where the CO2 is offload (for you to breathe out) and the cycle starts again.
So where can things go wrong and where can we have improvements in this system? Well, these are many. We'll look at lungs, heart, blood, circulatory system and cells.
Lungs
You need lung volume; you need your lungs to properly expand and contract to exchange the “used air” for the “new air”; you need to get the new air down the pipes to the alveoli; you need proper conditions for O2 to diffuse into the blood; you need working alveoli. You need enough RBC to pick up the O2 and enough Hb in the RBC to carry it all.
If you have asthma, your pipes are inflamed, making the openings narrow. It is hard to get new air in and old air out – like using a really narrow straw. If you have COPD (like emphysema or chronic bronchitis) you have problems. Emphysema destroys the small airways and causes them to collapse – this reduces the alveoli available for gas exchange. Chronic bronchitis makes excessive mucous in the broncii – and one effect is that mucuos makes it more difficult for O2 to get across the alveoli walls into the blood. Other than avoiding diseases or improving them up to your “normal” there isn't much that training does for the lungs. Your lungs are the size they are and your vital capacity (lung volume) is whatever your body size says it is.
RBC & Hb & circulation
This is a little like a logistics problem. Lets say your packing college students into phone booths, four to a booth, and then transporting the booths on flat bed trucks. You want to transport the maximum number of students per minute to work in your factories. Assume you have an endless supply of college students. First you need lots of trucks (RBC) and you need them to be full to capacity with empty phone booths. You need to get the trucks close to the students so they can pile in quickly, and then you can race off to the factories.
If you are anemic and not making enough Hb, you don't have enough phone booths. If you are iron deficient, you hare not making enough phone booths. If you have a low RBC count, you don't have enough trucks. If you're really in trouble, you're short on trucks, and they each are carrying less than their capacity of phone booths. If you have sickle-cell anemia, most of your phone booths are deformed and can't hold students and make the trucks misshapen too. If you have sickle cell trait (a carrier), you might only have a few misshapen phone booths and you don't really have any problems unless you are in an area with fewer students than usual (like high altitudes).
If you move to an area with relatively fewer students available (high altitude), your body will adapt by building more trucks & phone booths so you can get the same amount of students to your factories from the smaller pool of students. If you have too many RBC, you can get gridlock on the highway, but this is a fairly rare problem. If you step up demand in your factories (exercise), to a certain extent your body will build more trucks & phone booths to meet the increased demand, but there are limits. This is why athletes often train or live in higher altitudes to make more RBC & Hb and then compete at lower altitudes.
The highways and offramps and streets to the factories have to be adequate to handle the traffice load. That is, you must have enough capillaries near the working muscle to supply the cells' needs. If you exercise, your body will build new capillaries to increase the flow of O2 in and CO2 out.
Heart
The heart needs to pump regularly and with force – think of a sponge filled with water – you can barely squish it and get a little water out or you can give it a might squeeze and get a lot of water out per pump. You need a big sponge (heart size), a strong squeeze and enough water (blood volume) to move things along.
Under the right (good) physiologic conditions, your heart can increase its capacity (bigger sponge) and increase its muscle to squeeze harder (increase stroke volume). Regular exercise can also increase blood volume over time, which increases the amount that fills the heart each cycle. There is a mechanism that the more the heart is stretched by the returning blood, the harder it can contract – and thereby increase stroke volume (Frank-Starling mechanism). So this increased stroke volume delivers more blood per stroke to the cells.
Cells
The organelle in the cell that is the primary user of O2 is the mitochondria. This is the factory that produces energy – the last stop for our students. If you exercise and increase the energy demands on your body, your body will respond by building more factories (mitochondria) and more roads to the area (more capillaries) to deliver more O2.
So – lets summarize – how can training increase your VO2 max? What limits VO2 max – the delivery system or the capacity to use O2?
In untrained people, the first thing that happens is that the usage capacity is increased. Capillaries increase, mitochondrial density increases, enzymes needed to support cellular respiration are increased. At first, you have adequate delivery but need to step up consumption. Later, as you become a trained athelete, the delivery system seems to be the limiting factor. This is why the elite athletes turn to high altitude training or, for the unscrupulous, things like blood doping and EPO loading.
This is why, as we exercise, we can all chant with Covert Bailey "I'm building better butter burners...I'm building better butter burners" - as we increase our capacity to use O2.
In the mean time, if I haven't totally turned you off to the concept of VO2 Max – here are some articles by real writers:
good explanation of the concept
http://home.hia.no/~stephens/vo2max.htm (http://home.hia.no/%7Estephens/vo2max.htm)
how do you improve it ?
http://www.coolrunning.com/major/97/training/hampson.html
(http://www.coolrunning.com/major/97/training/hampson.html)
Respiratory Physiology
http://www.medicine.mcgill.ca/physio/resp-web/intr-idx.htm
Heart adaptations to Exercise
http://home.hia.no/~stephens/hrttrn.htm (http://home.hia.no/%7Estephens/hrttrn.htm)
Other Exercise Adaptations
http://home.hia.no/~stephens/timecors.htm (http://home.hia.no/%7Estephens/timecors.htm)
just FYI: HIIT in kids with asthma and effects on VO2 max
http://tinyurl.com/jz5c8
postscript:
I can't find the article now, but I recently read an article by the physiologist who has tested Lance Armstrong over the years. Lance has amazing VO2 max (about 85 ml/kg/min) and he also can generate a great deal of power for a long period of time. Here's the thing – a normal adult male might have 45 ml/kg/min – and a highly trained perons might get up to 60 ml/kg/min. After Lance's cancer treatments, and without really returning to much training, he was tested. His de-trained VO2 max was at the level of a highly trained normal person. And after training again, he returned to his prior level. I'll keep looking for that reference.
Technically, I'll be talking about V-dot O2 max (written as http://jap.physiology.org/content/vol98/issue4/fulltext/1371/f1.gifO2 ) (but I'm too lazy to keep formatting it that way each time). The “dot” in V-dot indicates that we are talking about a rate and not an absolute value. V-dot O2 max refers to the maximum amount of O2 that a person can utilize in a period of time. It can either be expressed in absolute units like L O2 per minute, or in size adjusted units of ml O2/kg/min. The “dot” in V-dot indicates that we are talking about a rate and not an absolute value. But only physio texts call it V-dot or bother to write with the V and the little dot ahove – so I'll quit that and just call it VO2 max – but you remember what it means.
I'll reference some good physiology sites & articles discussion VO2 max at the end. Exercise Physiology is one of my favorite subjects.
You all remember that the endpoint of cellular respiration is the reduction of O2 to H2O while producing ATP. So, the amount of O2 that you can maximally consume (use up) is an indirect measure of how much energy you are able to produce at your max capacity. What can influence VO2? Well, let's look at the road that O2 travels to get to those cellular factories we call mitochondria. First, air (at 21% O2) has to enter your lungs and get down to your alveoli. Then the O2 has to diffuse across the alveoli and get picked up by the hemoglobin (Hb) in red blood cells (RBC). Each Hb molecule can bind up to 4 O2 molecules. Hb has iron as a main component.
Your now oxygenated blood goes from the lungs to the left side of the heart, where it is squirted out into your aorta and on to the rest of the cells in your body. Once it finds a target tissue (like skeletal muscle) and the blood is in the capillary bed, the Hb releases the O2 which again has to diffuse to its destination – your cell. The O2 makes its way to the mitochondria in the cell where it can act as the final electron receptor and be reduced to water – as you are making ATP . The now deoxygenated blood flows back through the venous system (carrying CO2) and enters the right side of the heart. The heart pumps this deoxygenated blood to the lungs, where the CO2 is offload (for you to breathe out) and the cycle starts again.
So where can things go wrong and where can we have improvements in this system? Well, these are many. We'll look at lungs, heart, blood, circulatory system and cells.
Lungs
You need lung volume; you need your lungs to properly expand and contract to exchange the “used air” for the “new air”; you need to get the new air down the pipes to the alveoli; you need proper conditions for O2 to diffuse into the blood; you need working alveoli. You need enough RBC to pick up the O2 and enough Hb in the RBC to carry it all.
If you have asthma, your pipes are inflamed, making the openings narrow. It is hard to get new air in and old air out – like using a really narrow straw. If you have COPD (like emphysema or chronic bronchitis) you have problems. Emphysema destroys the small airways and causes them to collapse – this reduces the alveoli available for gas exchange. Chronic bronchitis makes excessive mucous in the broncii – and one effect is that mucuos makes it more difficult for O2 to get across the alveoli walls into the blood. Other than avoiding diseases or improving them up to your “normal” there isn't much that training does for the lungs. Your lungs are the size they are and your vital capacity (lung volume) is whatever your body size says it is.
RBC & Hb & circulation
This is a little like a logistics problem. Lets say your packing college students into phone booths, four to a booth, and then transporting the booths on flat bed trucks. You want to transport the maximum number of students per minute to work in your factories. Assume you have an endless supply of college students. First you need lots of trucks (RBC) and you need them to be full to capacity with empty phone booths. You need to get the trucks close to the students so they can pile in quickly, and then you can race off to the factories.
If you are anemic and not making enough Hb, you don't have enough phone booths. If you are iron deficient, you hare not making enough phone booths. If you have a low RBC count, you don't have enough trucks. If you're really in trouble, you're short on trucks, and they each are carrying less than their capacity of phone booths. If you have sickle-cell anemia, most of your phone booths are deformed and can't hold students and make the trucks misshapen too. If you have sickle cell trait (a carrier), you might only have a few misshapen phone booths and you don't really have any problems unless you are in an area with fewer students than usual (like high altitudes).
If you move to an area with relatively fewer students available (high altitude), your body will adapt by building more trucks & phone booths so you can get the same amount of students to your factories from the smaller pool of students. If you have too many RBC, you can get gridlock on the highway, but this is a fairly rare problem. If you step up demand in your factories (exercise), to a certain extent your body will build more trucks & phone booths to meet the increased demand, but there are limits. This is why athletes often train or live in higher altitudes to make more RBC & Hb and then compete at lower altitudes.
The highways and offramps and streets to the factories have to be adequate to handle the traffice load. That is, you must have enough capillaries near the working muscle to supply the cells' needs. If you exercise, your body will build new capillaries to increase the flow of O2 in and CO2 out.
Heart
The heart needs to pump regularly and with force – think of a sponge filled with water – you can barely squish it and get a little water out or you can give it a might squeeze and get a lot of water out per pump. You need a big sponge (heart size), a strong squeeze and enough water (blood volume) to move things along.
Under the right (good) physiologic conditions, your heart can increase its capacity (bigger sponge) and increase its muscle to squeeze harder (increase stroke volume). Regular exercise can also increase blood volume over time, which increases the amount that fills the heart each cycle. There is a mechanism that the more the heart is stretched by the returning blood, the harder it can contract – and thereby increase stroke volume (Frank-Starling mechanism). So this increased stroke volume delivers more blood per stroke to the cells.
Cells
The organelle in the cell that is the primary user of O2 is the mitochondria. This is the factory that produces energy – the last stop for our students. If you exercise and increase the energy demands on your body, your body will respond by building more factories (mitochondria) and more roads to the area (more capillaries) to deliver more O2.
So – lets summarize – how can training increase your VO2 max? What limits VO2 max – the delivery system or the capacity to use O2?
In untrained people, the first thing that happens is that the usage capacity is increased. Capillaries increase, mitochondrial density increases, enzymes needed to support cellular respiration are increased. At first, you have adequate delivery but need to step up consumption. Later, as you become a trained athelete, the delivery system seems to be the limiting factor. This is why the elite athletes turn to high altitude training or, for the unscrupulous, things like blood doping and EPO loading.
This is why, as we exercise, we can all chant with Covert Bailey "I'm building better butter burners...I'm building better butter burners" - as we increase our capacity to use O2.
In the mean time, if I haven't totally turned you off to the concept of VO2 Max – here are some articles by real writers:
good explanation of the concept
http://home.hia.no/~stephens/vo2max.htm (http://home.hia.no/%7Estephens/vo2max.htm)
how do you improve it ?
http://www.coolrunning.com/major/97/training/hampson.html
(http://www.coolrunning.com/major/97/training/hampson.html)
Respiratory Physiology
http://www.medicine.mcgill.ca/physio/resp-web/intr-idx.htm
Heart adaptations to Exercise
http://home.hia.no/~stephens/hrttrn.htm (http://home.hia.no/%7Estephens/hrttrn.htm)
Other Exercise Adaptations
http://home.hia.no/~stephens/timecors.htm (http://home.hia.no/%7Estephens/timecors.htm)
just FYI: HIIT in kids with asthma and effects on VO2 max
http://tinyurl.com/jz5c8
postscript:
I can't find the article now, but I recently read an article by the physiologist who has tested Lance Armstrong over the years. Lance has amazing VO2 max (about 85 ml/kg/min) and he also can generate a great deal of power for a long period of time. Here's the thing – a normal adult male might have 45 ml/kg/min – and a highly trained perons might get up to 60 ml/kg/min. After Lance's cancer treatments, and without really returning to much training, he was tested. His de-trained VO2 max was at the level of a highly trained normal person. And after training again, he returned to his prior level. I'll keep looking for that reference.