Hct/Hgb levels and power

rmur17

okay this thread is not about doping! Let's say a given cyclist was borderline anemic for several years in the 37-39 Hct (around 125-130 Hgb) range when tested -- for whatever reasons - perhaps a combination of an iron-poor diet, dilutional effects of training etc.

A starting baseline was Hct 38.1, Hgb 127 about eighteen months ago.

With an improved diet and modest supplementation of iron over ~nine months, last spring ('07) this person's blood level has risen to 40.5% Hct (135 Hgb).

A recent test after another ~ nine month span was 43.4 Hct (144 Hgb).

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.

i've searched some old threads and, although suggestive, I'd like to hear current thoughts from those in the know.

thanks

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rmur

Urkiola2

Hello rmur17. About your question I would say that in the 1st place if that cyclist was competing with a 12.5-13 g/dL of Hgb that seems very low to me so it is possible that as you point out he/She was anemic or pseudoanemic, especially being confirmed than now he/she has a Hgb of 14.4 and Hct of 43.4%. This means that during that period of anemia or pseudo-anemia he/she was underperforming 100% for sure and just by correcting his/her levels he/she should notice an important improvement in condition. It is difficult though and maybe some matemathitians/engineers out there can help us out in predicting FTP based on the numbers before this physiological status and the new status. And even that it would be very theorical. The bottom line is that he/she sould be performing better with proper training and it is extrenely important to take care of nutrition/training dose and recovery so that he/she does not fall again in the whole.

I hope it helped. Not much info but I hope it helped.

Cheers.

ctgt

I'm also interested in the answer to this question. I have given blood 50+ times, and never ever was refused for low iron until I started training more seriously. In the past 4 years, I have been deferred once, and 2-3 times they re-tested my HgB just to make sure (my blood didn't sink fast enough in the solution). Their threshold to give blood is 125.

One more question: What is the relationship between the HgB levels that Canadian Blood Services measure for, and the HcT levels that we all as cycling fans read about so much? Do they automatically vary in lockstep with each other, or are there other factors?

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HSCoach2 on other cycling forums

Urkiola2

It is very kind of you to donate blood since it is a necessity in many hospitals...I just hope that finally all the new blood substitution solutions going on the clinical trials can finally be cleared and be used for the good og humanity and not for the enrichement of athletes and some people around them..

Anyways, I don´t know the Canadian theshold to give blood but if they refused you because your Hgb was 12.5 then you (I am assuming you are a male) could be in trouble in terms of performance. If you want to compete I would donate blood during the off-season, because during the season you can end up under anemic or pseudoanemic conditions. One bag of blood (pint) it is about 450ml and that represents, and pretty accurately..a drop of about 3%Hct and 1g/dL of Hgb. Also you have to check Ferritin levels which is a major player. Many people (including many physicians) only pay attention to iron levels. However iron levels are very voluble and they don´t necessarely reflect the iron status of your body. Ferritin is the storage form of iron and that is what you need to look for in the future. Very low ferritin levels take several months to get back up to normal with iron replacment therapy and proper rest. So that is something you should taking into account.

I hope it helped.

Cheers

Alex Simmons

I have one 50+ y.o. female athlete that is susceptible to low ferritin levels, something we look out for when performance stall/falls.

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http://alex-cycle.blogspot.com/
http://www.cyclecoach.com/

sidewind

Some numbers from
http://www.ncbi.nlm.nih.gov/sites/entrez


Influence of blood donation on O2 uptake on-kinetics, peak O2 uptake and time to exhaustion during severe-intensity cycle exercise in humans.

Burnley M, Roberts CL, Thatcher R, Doust JH, Jones AM.
Department of Sport and Exercise Science, University of Wales Aberystwyth, Ceredigion, UK.

We hypothesized that the reduction of O2-carrying capacity caused by the withdrawal of approximately 450 ml blood would result in slower phase II O2 uptake (VO2) kinetics, a lower VO2peak and a reduced time to exhaustion during severe-intensity cycle exercise. Eleven healthy subjects (mean +/- S.D. age 23 +/- 6 years, body mass 77.2 +/- 11.0 kg) completed 'step' exercise tests from unloaded cycling to a severe-intensity work rate (80% of the difference between the predetermined gas exchange threshold and the VO2peak) on two occasions before, and 24 h following, the voluntary donation of approximately 450 ml blood. Oxygen uptake was measured breath-by-breath, and VO2 kinetics estimated using non-linear regression techniques. The blood withdrawal resulted in a significant reduction in haemoglobin concentration (pre: 15.4 +/- 0.9 versus post: 14.7 +/- 1.3 g dl(-1); 95% confidence limits (CL): -0.04, -1.38) and haematocrit (pre: 44 +/- 2 versus post: 41 +/- 3%; 95% CL: -1.3, -5.1). Compared to the control condition, blood withdrawal resulted in significant reductions in VO2peak (pre: 3.79 +/- 0.64 versus post: 3.64 +/- 0.61 l min(-1); 95% CL: -0.04, - 0.27) and time to exhaustion (pre: 375 +/- 129 versus post: 321 +/- 99 s; 95% CL: -24, -85). However, the kinetic parameters of the fundamental VO2 response, including the phase II time constant (pre: 29 +/- 8 versus post: 30 +/- 6 s; 95% CL: 5, -3), were not altered by blood withdrawal. The magnitude of the VO2 slow component was significantly reduced following blood donation owing to the lower VO2peak attained. We conclude that a reduction in blood O2-carrying capacity, achieved through the withdrawal of approximately 450 ml blood, results in a significant reduction in VO2peak and exercise tolerance but has no effect on the fundamental phase of the VO2 on-kinetics during severe-intensity exercise.

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These are layman's opinions, expressed in language no self-respecting scientist woul be using.

INCE

Interesting questions in the opening post. I did not see any direct answers yet as to how reduction/ increase in hct/hgb affects power specifically.Let me try.

Generally, I’d think the relationship would be tied to the efficiency (economy) of the individual at the time of testing.I will make some very broad but realistic assumptions:
-End aerobic zone at ventilary theashold,
-efficiency=25%,
-power vs. VO2 linear,
-V02 vs. hgb/hct linear,
-equilibrium stable conditions,
-withdrawal of 450 ml of whole blood=drop of 3%Hct,=1g/dL in Hgb

I would theorize that hct change from 38.1% to 43. 4% (13.4% change over starting) would be equivalent to taking two units of whole blood and would increase VO2 by 8% and wattage at ventilary threashold by 2-3%. Sounds like it its not much but significan. Does it make sense?

rmur17

thanks for the reply. I don't have any ex. phys. training so I struggle with things like this.

Now can I ask how you arrived at the 8% for Vo2max but only 2-3% for threshold?

thanks again

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rmur

Steve_B

I am interested in this topic myself. My last blood test (December) says:
Hematocrit = 39.8 % (expected range 42 - 52)
RBC = 4.33 M/UL (expected range 4.50 - 5.50)
Hemoglobin = 13.7 G/DL (expected range 13.5 - 17.0)
No Ferritin results listed.

I was probably a little dehydrated for this test and I believe that is supposed to elevate 'crit results so it could be even worse than this.

My doctor didn't mark the RBC and 'crit as anything to worry about. Hmmmm... I'm going to call him to get a copy of the previous two blood tests to see if this has been a chronic issue.

kant314

is there a relationship between Hemoglobin and hct?

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rmur17

we seem to have lost Urkiola2 in the spam .

Roughly speaking, Hct% = Hgb (g/dl) x 3

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rmur

Urkiola2

Sorry, I have a cold these days and have a slow hand to write these days.
My hand will get a bit faster soon...

The relationship with Hct and Hgb is: 1g/dL of Hgb multiplied by 2.96 to get your % of Hct. It is a mathematical formula and as always, there will be some exceptions. However I have seen thousends of tests and the relationship is quite accurate. Mathematically speaking is 2.96 although a multiplication by 3 is usually aplied widely.

Cheers.

jsirabella

I am surprised with your background and knowledge I did not see a post in the Sodium Phosphate thread. I asked a few riders here who race about it and they all gave me a strange look that never heard of it. Have you any experience with it? Ofcourse you can post here or in that thread not to take it off subject.

-Js

Urkiola2

Sorry, I am just not into ergogenic aids (legal or ilegal) discussions. I don't want to get into that.