In the movie, This Is Spinal Tap, there’s a scene where the lead guitarist of the band is showing off his amplifiers, when the camera zooms in on the knobs controlling volume. Only, there’s a twist. The knobs go to 11, instead of just 10. As the rocker says, “It’s one louder, isn’t it?”
Similarly, turning your blood volume up to 11 can give your performance a boost on the trails. Smart training adds an extra setting to your blood volume knob (called hypervolemia), and you might not even know it. So let’s break it down.
A 2000 review article in “Medicine & Science in Sport & Exercise” deconstructed some of the blood volume basics. According to the article, blood volume is the sum of erythrocyte volume (red blood cells) and plasma volume (mostly water plus some dissolved proteins, glucose, clotting factors, electrolytes, hormones, carbon dioxide and oxygen). This paragraph sounds like a vampire reading a nutrition label.
Red blood cells transport oxygen, while more plasma lets your heart pump more volume per beat per minute (greater cardiac output). Red blood cell increases usually occurs over weeks and months, while plasma volume responds more rapidly (days or even hours). They can change independently of one another to change total blood volume. This one sounds like a vampire reading a cookbook.
So blood volume is a big determinant in performance, and it can change over time. How can we turn it up to 11 with training? There are three main principles to think about.
Train consistently, mixing intensities
The main avenue to increasing blood volume is training consistently. In untrained individuals, within just 24 hours of training, it can increase by around 10 percent due to plasma volume expansion. After two to three weeks, many studies measure red blood cell increases, increasing progressively thereafter. In studies, the amount of blood volume change is most influenced by initial fitness level (higher fitness means less room for blood volume to grow), training intensity (mixing intensities and including some hard workouts is better) and type of activity studied. (Interesting note: being in space reduces blood volume a ton, so try to avoid space travel during important training blocks).
The main takeaway? Consistent, long-term training is what matters most, with no shortcuts to improvement over time. For example, a 2013 study in the “International Journal of Sports Physiology & Performance” found significant increases in blood volume after seven weeks of endurance training with intensity mixed in, with similar findings echoed across many studies.
What accounts for the blood volume change? The review study mentioned in the intro broke down a bunch of studies into two cohorts, one that had training durations of less than 12 days, and one with more than 21 days. In the short duration studies, participants had an 11 percent increase in plasma volume and no increase in red blood cells. In the longer duration studies, participants had similar plasma volume change and a 9 percent increase in red blood cells. Put it all together, and the longer-term group improved VO2 max by about twice as much. In other words, fitness increases from blood volume expansion can compound on each other over time (to a point).
So blood volume can rise relatively rapidly with smart training, and the longer the training period the better. But it can fall quickly too, as explained in this 2007 review from the “American Journal of the Medical Sciences.” In fact, a seminal study from the 1980s in the “Journal of Applied Physiology” found decreases of 5 to 12 percent after just a few days of inactivity. While that is mostly plasma volume that will bounce back quickly, too much stop-and-start training will eventually put a stop to running progression and make all your runs harder. That’s why the first run after a few days off might make you feel like a constipated water buffalo, even though you won’t lose any fitness in that time.
In your training, strive for consistency over epicness. Build up to at least five days of running a week if you can, mixing in a day or two of higher intensity efforts. Cross training that supports your running is great too. Then, you might get the benefit of the blood volume positive feedback loop: increases lead to more enjoyable and faster training, which makes blood volume increase a little more, making you even faster. Eventually, it all will likely stabilize at some higher set point, but that’s a good problem to have.
Use altitude if you can
The hormone erythropoietin (EPO) probably rings a bell, especially if you once had to sadly remove a Livestrong bracelet sometime around 2010. In addition to its sinister uses in pro cycling and other endurance sports, EPO is a natural hormone that responds to training and altitude. Due to natural EPO production, people that have lived at high altitude their whole lives have higher blood volume than sea-level dwellers, mostly due to increased red blood cells. Tons of studies show how training at altitude can increase red blood cells after a couple weeks exposure. Most elite training groups spend time at altitude for that reason.
In your training, if you live at low altitude, try to schedule family vacations at high elevations (or even better, move to Flagstaff). A couple-week stint at elevation can make a big difference in red blood cell volume. Some pro athletes even use altitude-generation systems, like Hypoxico, which let you simulate altitude with a mask or a tent. Just make sure your significant other is on board.
Heat is your friend
You may have heard people talking about the magical performance benefits of the sauna. The reason is not that being around a bunch of sweaty, hairy, naked people makes you run extra fast out of the sauna. It’s that heat adaptation increases blood volume.
At rest, plasma volume expands by around 5 percent in the hottest months, and contracts by 3 percent in the coldest months (the technical term should be “shrinkage”). When heat sources like the sauna are introduced, plasma volume can increase by as much as 20 percent in some people for a short period. For example, a 2015 study in the “European Journal of Applied Physiology” found big increases in blood volume in highly trained cyclists after just four exposures to post-exercise sauna. As this 2016 review outlines, heat stress could stimulate EPO production too.
For your training, as summer comes around, don’t be shy about running in the heat. It’s your friend, giving your blood volume an extra boost. On top of that, some of the athletes I coach will do 20 to 30 minutes in a dry sauna after exercise, followed by 45 minutes without cooling off or rehydrating (enhancing the blood volume stress, particularly before hot-weather races like the Western States 100). Just be sure that any routine is approved by your doctor first.
On top of training influences, it’s important to have enough iron to build red blood cells and to avoid chronic dehydration, which reduces plasma volume. For most athletes, the big takeaway of the literature on blood volume is just to train consistently, not shying away from heat or mountains, while eating enough iron-rich foods (or supplementing) to get the maximum bang for your training buck.
—David Roche partners with runners of all abilities through his coaching service, Some Work, All Play.