What's Cool In Road Cycling

How Blood Donation Affects Performance

What happens with blood donation to your body and your performance?

Blood – it’s in you to give. Donating blood is a wonderful selfless act to help others. How might you need to adapt your training around your blood donation schedule?



Donating blood is something that I have been doing routinely for the past 10 years or so, especially as I apparently have a relatively rare blood type: B negative. I think donating is something that is important, as those donations can help save lives for cancer, trauma, or burn patients.

However, donating blood certainly is not as easy as writing a check. No, it means giving up your hard-earned red blood cells. Don’t doping athletes try to increase their red blood cell (RBC) count or erythropoietin (EPO)? After all, cycling is an aerobic sport, so isn’t giving up some of your aerobic fitness counterintuitive? So, should you be donating as a casual or competitive cyclist? I hope to help answer that in this month’s Pez Toolbox article.

What Happens When You Donate Blood?

A whole-blood donation involves taking one pint (~500 mL) of blood. For most humans, this represents about 10% of your total blood volume. This means that you’ll be losing about 10% of your RBCs and the crucial oxygen-carrying hemoglobin within. In theory, this means forfeiting about 10% of your body’s ability to deliver oxygen to your working muscles during those hard intervals. For this reason, the Red Cross recommends avoiding strenuous activity for the first ~24 hours after donating.

Immediately after donating blood, your body works hard to replenish what was lost. Just 24 hours after donating, your body can replace the lost plasma (1), or the watery base of your blood. Therefore, drinking water before and after donating is so crucial.

Your platelets, or the proteins responsible for helping your blood clot, are replenished after about 72 hours (2).

Unfortunately for us as athletes, the RBCs, or the oxygen-carriers, are the most time-consuming part of the blood to regenerate, taking approximately 4-6 weeks (2). To help expedite the replenishment of RBC’s, it is important to include foods that are high in iron (red meats, leafy greens, etc.) into your diet. This 3 to 4 week lag in replenishing RBC’s is what may cause many athletes to think twice about donating, but what does the science have to say about potential losses in performance?


Impact on Performance

Unsurprisingly, there are several studies that have shown reduced aerobic performance after donating (3-6). The reductions in athletic performance have been measured through decreases in VO2max (the maximum amount of oxygen your body can process in a minute) as well as tests to exhaustion. To help you understand the magnitude of the loss in performance, Dellweg & colleagues reported a decrease of ~9% in VO2max and ~13% decrease in time to exhaustion after donating 500 mL of blood (5). This is relatively unsurprising after donating approximately 10% of your total blood volume.

How long does this impaired performance last? Judd & colleagues reported that exercise performance returned within about 3 weeks (6). Note that this is a bit quicker than the 4-6 weeks that the Red Cross suggests (1).

When should you donate?

If you would like to consider helping critical patients in need by donating blood, then it is obviously best to avoid donating in the critical weeks leading up to your main target events. In fact, I would not recommend donating ~8 weeks before any planned competition. Of course, this is purely based on performance as the sole consideration and priority.

On the other hand, November & early December are great times to donate since many of us are entering the off-season and may be reducing your training or switching to relatively low-intensity training. Your plasma volume and RBC’s will be ready to go by the time you ramp up your winter training.


That’s all for this month! I hope you found this article interesting and relevant, and that you may consider becoming a donor too! Stay safe, ride fast, and I will see you all next month!

giving blood


Donation FAQs. (2016). The American National Red Cross. http://www.redcrossblood.org/donating-blood/donation-faqs.

Ruel, J. (2011). Whole blood & platelets: what’s the difference? Stanford Blood Center. http://bloodcenter.stanford.edu/blog/archives/2011/07/whole-blood-pla.html.

Fritsch, J., Winter, U.J., Reupke, I., Gitt, A.K., Berge, P.G., & Hilger, H.H. (1993). Effect of a single blood donation on ergo-spirometrically cardiopulmonary performance capacity of young healthy probands. Zeitschrift fur Kardiologie, 82(7). Abstract. http://www.ncbi.nlm.nih.gov/pubmed/8379242.

Burnley, M., Roberts, C.L., Thatcher, R., Doust, J.H., & Jones, A.M. (2006). Influence in blood donation on O2 uptake kinetics, peak O2 uptake, and time to exhaustion during severe-intensity cycle exercise in humans. Experimental Physiology, 91(3). http://onlinelibrary.wiley.com/doi/10.1113/expphysiol.2005.032805/full.

Dellweg, D., Siemon, K., Mahler, F., Appelhans, P., Klauke, M., & Kohler, D. (2008). Cardiopulmonary exercise testing before and after blood donation. Pneumologie, 62(6), Abstract. http://www.ncbi.nlm.nih.gov/pubmed/18535983.

Judd, TB., Cornish, S.M., Barss, T.S., Oroz, I., Chilibeck, P.D. (2011). Time course for recovery of peak aerobic power after blood donation. Journal of Strength & Conditioning Research, 25(11). http://journals.lww.com/nsca-jscr/pages/articleviewer.aspx?year=2011&issue=11000&article=00014&type=abstract.


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