Hct/Hgb levels and power

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I defenetely agree that it is quite impossible to predict an exact performance or a %gain in performance solely based on Hct%. To me there is no way you can do that and I agree with you. However, and please don't get offended, as this is a friendly argument I always have with cardiologists and also anesthesiologists because they look more at the big picture and hemodynamics than at the cellular level. There are many studies showing that a decrease in Hgb levels (from a physilogical individual homeostasis) and therefore Hct will result in impaired exercise performance due to a decreased O2 carrying capacity. Otherwise the term "anemia" or "pseudoanemia" would not exist. As a matter of fact, it is thought that Anemia is the no.1 disease in the world...However in the vast majority of cases is not disgnosed simply because to carry a regular life a person would not tell unless it is a severe anemia. I have seen people as you as well for sure with Hct's of 30% and barely feeling it for the day-day activities...or others with 25% and just feeling a bit tired...something that it is still amazing to me (used to work with athletes) and you may be right due to the increased cardiac output to make it up for the lower "viscosity". However this is not the case of athletes, that I can tell you for sure. If your Hct is 45% and you decrease it to 38% you bet you will be decreasing your performance and you will struggle more on the races. As I mentioned that is one of the many "features" of overtraining and I see that everyday. You can tray it yourself. Withdraw 2 bags of blood (roughly 1L). Filter the contents except the erythrocytes and reinfuse the plasma with the rest of elements in it back so that you will recover your plasma volume and electrolyte and other elements to achieve homeostasis. The only thing you would be missing would be the packed red blood cells. Then go on your bike and go racing or a high intensity training. Regardless of the efforts of your heart, arteries, arterioles and any other vessels as well as any hemodynamic mechanism ossible to "save your butt" you will hurt on the bike like yoiu never had before, that is for sure.
About Cardiac Output, yes there is a limit. THat is the endocardium. Your heart can try to increase it but there is an anatomical self-defense mechanism by the one your Cardiac Output cannot increase more and that is the endocardium. That is a typical question of residency/medical/physiology exams to "trick" you.

Anyways, I am tired of writing too much today...I think I may bee anemic..:) ..Just kidding!.

Cheers.Don't take my objections to some of what you are saying as my thinking you are attacking me. This is more of an academic discussion and we are in general agreement except for one or two small points that are worthy of further discussion. I am not offended. I appreciate your tone.

First, I think you meant to say that CO is limited by the pericardium, not the endocardium. I would agree with this if we are talking about acute changes, but not if we are talking the chronic ability to adapt.

You are not the only one to believe the heart is the limiter to our ability to exercise but, IMHO, there simply is no physiological limit, except as our ability to stress the cardiovascular system to effect the increases. If we can figure out a way to regularly exercise more muscle mass the heart will adapt to the stress, whatever it is. There is zero evidence that there is an absolute maximum yet the evidence to support the cardiovascul system is adaptable is several and compelling. First, our hearts grow as we do. They don't grow simply because we get bigger but they grow because, as we get bigger, there is more demand placed upon it. Those who push the stresses even more than the average, the endurance athlete, ends up with a bigger heart than average, affectionately known as "the athletes heart". Further evidence exists in the form of other mammals. All mammals have pretty much the same cardiovascular physiology. Cardiac output and heart size is related to the mass of the animal (which also relates to the surface area which corresponds with how easy or hard it is to maintain temperature) with a high degree of precision yet all mammals are starting with essentially the same cardiovascular physiology, these cardiovascular systems are the size they are because they have adapted to the daily stresses they see. There is no physiological reason, that I am aware of, the human heart could not become the equivalent of the elephants heart in both size and pumping capacity if it were subjected to the same ongoing daily stresses (and if there were room in the chest for it to expand).

Don't take my objections to some of what you are saying as my thinking you are attacking me. This is more of an academic discussion and we are in general agreement except for one or two small points that are worthy of further discussion. I am not offended. I appreciate your tone.

First, I think you meant to say that CO is limited by the pericardium, not the endocardium. I would agree with this if we are talking about acute changes, but not if we are talking the chronic ability to adapt.

You are not the only one to believe the heart is the limiter to our ability to exercise but, IMHO, there simply is no physiological limit, except as our ability to stress the cardiovascular system to effect the increases. If we can figure out a way to regularly exercise more muscle mass the heart will adapt to the stress, whatever it is. There is zero evidence that there is an absolute maximum yet the evidence to support the cardiovascul system is adaptable is several and compelling. First, our hearts grow as we do. They don't grow simply because we get bigger but they grow because, as we get bigger, there is more demand placed upon it. Those who push the stresses even more than the average, the endurance athlete, ends up with a bigger heart than average, affectionately known as "the athletes heart". Further evidence exists in the form of other mammals. All mammals have pretty much the same cardiovascular physiology. Cardiac output and heart size is related to the mass of the animal (which also relates to the surface area which corresponds with how easy or hard it is to maintain temperature) with a high degree of precision yet all mammals are starting with essentially the same cardiovascular physiology, these cardiovascular systems are the size they are because they have adapted to the daily stresses they see. There is no physiological reason, that I am aware of, the human heart could not become the equivalent of the elephants heart in both size and pumping capacity if it were subjected to the same ongoing daily stresses (and if there were room in the chest for it to expand).
1st of all....I have to apologize because I can't believe I said Endocardium!!!:confused: . How embarrasing!. I had a long ride today and have been with a cold this week and I think tyhat my brain is not recieving too much glucose...What a dummass. Sorry about that mistake. I meant pericardium!.

2nd, I think we agree in all the terms you say and we could keep talking for hours about cardiac physiology and pathophysiology, especially if we get into hypertrophic cardiomyopathies and defenetely getting out of the post. I just was pointed out about the fact (seen and suffered by thousends and reported in scientific literature widely) that a decrease in Hgb/Hct due to, not a hemodilution nor hemodynamics situation, but an erythrocytopenia either acquried due to lack of iron, B12, folate, hemolysis...or idiopathic will elicit a decrase in exercise capacity, especially in a competitive athlete regardless of CO or any other hemodynamics compensations. But again I agree it is to me, at least, abosultely impossible to predict performance based on hct level to a such a specific degree of accuracy as posted here. There are just way too many players to just isolate one. However I still believe not only from literature but from every-practice and experience by me and other collegues that a decrease in carrying oxygen capacity to the muscle cells and therefore a lowr O2 avaliability is seen in people whose Hgb is decreased by either an acquired or idiopathic condition as mentioned before.

Cheers.

1st of all....I have to apologize because I can't believe I said Endocardium!!!:confused: . How embarrasing!. I had a long ride today and have been with a cold this week and I think tyhat my brain is not recieving too much glucose...What a dummass. Sorry about that mistake. I meant pericardium!.

2nd, I think we agree in all the terms you say and we could keep talking for hours about cardiac physiology and pathophysiology, especially if we get into hypertrophic cardiomyopathies and defenetely getting out of the post. I just was pointed out about the fact (seen and suffered by thousends and reported in scientific literature widely) that a decrease in Hgb/Hct due to, not a hemodilution nor hemodynamics situation, but an erythrocytopenia either acquried due to lack of iron, B12, folate, hemolysis...or idiopathic will elicit a decrase in exercise capacity, especially in a competitive athlete regardless of CO or any other hemodynamics compensations. But again I agree it is to me, at least, abosultely impossible to predict performance based on hct level to a such a specific degree of accuracy as posted here. There are just way too many players to just isolate one. However I still believe not only from literature but from every-practice and experience by me and other collegues that a decrease in carrying oxygen capacity to the muscle cells and therefore a lowr O2 avaliability is seen in people whose Hgb is decreased by either an acquired or idiopathic condition as mentioned before.

Cheers.It is the internet, sometimes our fingers go faster than our brains. So, we are in agreement.

Until the next "discussion". Cheers.

...
Overall the percentage change from 1.5 yrs ago was 13.4% and from nine months ago 7.2%.

If we assume the training volume and intensity, state of overall health, plasma volume etc. etc. was reasonably constant across this period such that the increase in Hgb/Hct truly reflect the hemoglobin status of the blood, what would one predict about the performance of the individual? We're mostly concerned about sustainable power to the pedals of course.

Or maybe more properly, the what would one expect to say about the performance potential of the individual relative to historic norms in the ~38% Hct range?

To keep it simple, let's focus on power @Vo2max or ~5MP and power at functional threshold FTP.


Rick, last year I've read from Dr. Coggan that transfer between HCT/HGB and VO2max would be around 50% but I can't find the reference, this is an older one (also from Dr. Coggan) in wattage:

If your hematocrit were higher, your VO2max, etc. would also be higher.
Figure about a 1:2 ratio (i.e., 10% increase in hematocrit, 5% increase
in VO2max).
http://groups.google.com/group/wattage/browse_frm/thread/a831aed1b396c37c/ace43fdbf3b54929?hl=en&lnk=gst#ace43fdbf3b54929

Your power at VO2max would be 3.6% and 6.7% higher, ceteris paribus:)