There’s not much that’s more essential to your running (and your life) than your blood.
The more oxygen-carrying power your blood has, the faster you can run. Without enough oxygen, your body is quickly plunged into acidosis, the deep burning sensation in your legs that you feel at the end of a race or a hard workout.
Blood donation and running performance
A 2013 study by David Hill, examined the short-term effects of donating blood and plasma on a cycling endurance test in nineteen test subjects. Each subject underwent a ride to exhaustion on a stationary bike before giving blood or plasma, and again two hours, two days, and seven days after the donation. The researchers measured both time to exhaustion and maximum oxygen consumption, or VO2 max, during each of the four tests.
Unsurprisingly, they found that both VO2 max and time to exhaustion were negatively impacted in the immediate aftermath of a whole blood donation.
VO2 max dropped by 15% and time to exhaustion decreased by 19% during the exercise test two hours after a blood donation. VO2 max was still 10% and 7% lower than pre-donation levels at two and seven days post-donation, respectively.
The results of plasma donation are more interesting.
Although the plasma donation resulted in no change in VO2 max at any point, time to exhaustion was decreased two hours post-donation, but not two days or one week out.
Hill et al. hypothesized that this was because the drop in overall blood volume from the plasma loss interfered with anaerobic capacity. Plasma volume is restored rather quickly, which explains why this phenomenon was not seen two days or a week later.
Hill et al. showed that whole blood donation still impaired performance a week after giving blood, but how long do the effects linger?
How long is performance impacted?
This issue was addressed by a 2011 study by T.B. Judd and other researchers at the University of Saskatchewan in Canada, who studied 12 subjects’ VO2 max before a blood donation and once every week for a month following the donation.
Like the previous study, Judd et al. found a marked decrease in VO2 max the day after blood donation.
Over the following weeks, the subjects’ VO2 max gradually returned to normal, reaching its pre-test value three weeks out from the date of the blood donation.
The one drawback to the above studies is that they used only moderately active people from the general population, not trained athletes. It stands to reason that a well-trained runner might experience a greater drop in fitness with loss of blood.
Changes in iron levels after blood donation
There’s one more issue with blood donation that deserves to be mentioned, and that’s iron levels.
When you donate blood, your body replaces the lost red blood cells by synthesizing new ones, a process which consumes iron stored in the form of ferritin.
A rigorous analysis of almost 3,000 blood donors by Clement Finch and other researchers at the University of Washington found that your body’s iron levels (as measured by serum ferritin) are negatively correlated with how often you give blood.
- A good time to donate is during the recovery time after your goal race when your body isn’t under the constant demands of a training season.
- Plan the donation around a rest day and follow with several days of short, easy effort until you begin to feel 100%.
- In the 4-5 days following your donation, throw out your watch! Your times are going to be slower (the research shows it) so just forget about pace and put some time on your feet.
- Stay hydrated and eat well before and after the donation. This will help you recover faster from the donation itself.
The bottom line when it comes to blood donation is that there will be a notable drop in your performance, but the research to date indicates that your body returns to normal after about three weeks.
There’s still more research needed on whether blood donation has an especially large impact on well-trained athletes, as is the case with some other performance inhibitors (like altitude), but if you don’t have any races for the next month, and you’re okay with your workouts being a bit slower for a few weeks, go ahead and donate blood.
One final consideration is your iron status: if you donate often, make sure you have your ferritin checked to be sure it’s not too low, especially if you have a history of low iron.
-Runners Connect; John Davis