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This article was originally published in the Jan/Feb 2011 issue of Inside Triathlon magazine.
Boulder, Colo., became an endurance Mecca in the 1970s, after exercise scientists discovered that living at high altitude changes blood chemistry in ways that enhance sea-level performance. Since then, exercise scientists have learned a great deal more about the relationship between altitude and endurance performance, and what they’ve learned suggests that Boulder’s mile-high elevation is one of the worst possible environments for endurance athletes to make their homes in. It’s not high enough to significantly change blood chemistry in most people, yet it’s also just high enough to significantly reduce performance in high-intensity workouts, so that athletes get a little less benefit from each quality session.
Forgive me if you’re reading this in Boulder. We’re just the messenger.
If you want to get mad at someone, get mad at Robert Chapman, an exercise physiologist at Indiana University and one of the world’s leading experts on the effects of altitude exposure on endurance performance. Chapman explains that the key thing his colleagues had wrong in the 1970s was the specific effect of training (versus living) at altitude on endurance performance.
“Historically, people had thought that training at altitude was beneficial for sea-level performance,” he says. “Slowly, over time, we started to realize that’s not necessarily the case. For many people, training at altitude is actually a negative, and it’s mainly because they train slower when they’re at altitude. And they also train at a lower oxygen uptake, so there’s less adaptive stimulus.”
The problem with training slower at high altitude is that it causes the neuromuscular system to miss out on some of the performance-boosting adaptations, including increased efficiency, that come from going faster. The problem with training at lower oxygen consumption levels is that it causes the metabolic system to miss out on some of the performance-boosting adaptations that come from consuming more oxygen. For example, high levels of lactate production during intense exercise stimulate the biogenesis of new mitochondria within muscle cells, which increases aerobic power. But fatigue occurs at lower blood lactate levels at high altitude. Not good.
According to Chapman, some athletes do experience an overall improvement in sea-level performance after a period of living and training at high altitude. But the gain comes entirely from the living at altitude part rather than the training at altitude part. The training at altitude part actually negates some of the potential gain they get from the living at altitude part. Meanwhile, the other half of the endurance athlete population experiences a net loss in sea-level performance as a result of living and training at high altitude.
Live High/Train Low
In the 1990s, the revelations about altitude led exercise scientists James Stray-Gundersen and Ben Levine to propose an alternative way to use altitude to increase endurance performance. This alternative became known as “live high/train low.” As the name suggests, this model entails living at high altitude to stimulate increased red blood cell production—which enhances endurance performance by boosting the blood’s capacity to deliver oxygen to the working muscles—and working out at low altitude, allowing the athlete to actually take advantage of those extra red blood cells to perform faster workouts that stimulate stronger fitness adaptations.
Stray-Gundersen and Levine tested their new model in a seminal 1997 study involving 39 college runners. They separated these runners into three groups. For 28 days, one group lived and trained at high altitude, a second group lived and trained at sea level, and a third group lived at high altitude and trained at low altitude. At the end of the period, both the live high/train high runners and the live high/train low runners exhibited increased red blood cell counts. But only the live high/train low runners showed improved performance. On average, these runners ran 13.4 seconds (or 1.5 percent) faster in a 5000 meter time trial after the intervention than before, while 5000 meter performance was unchanged in both the live high/train high and the live low/train low groups.
In tabular form, the results look like this:
Protocol Performance Improvement
Live Low/Train Low 0%
Live High/Train High 0%
Live High/Train Low 1.5%
Now, these are average results, and as such they mask the fact that some athletes do improve by living and training at high altitude, while others go backward. Chris Lieto finished second in the 2009 Hawaii Ironman after his first stint of living and training at high altitude in Mammoth Lakes, Calif. Although he did not engage in formal performance testing to prove that it worked, he says, based on subjective measures, “I feel it worked well.”
However, according to Chapman, even the fraction of the endurance athletes that benefits from living and training at high altitude is likely to get better results from live high/train low. That’s because they will get the same increase in red blood cell mass from living at high elevation while being able to perform at a higher level in workouts at lower elevation.
The only drawback of live high/train low is that it is terribly inconvenient. It requires that one live at an elevation of at least 6,000 feet for at least four weeks and drive down to an elevation of 4,000 feet or below for workouts. There are only a handful of locations in the U.S. where this is possible. In the Stray-Gundersen and Levine study, athletes lived in Park City, Utah, and drove to Salt Lake City for workouts. One could also live in Flagstaff, Ariz., and drive to Sedona; live in Taos, N.M., and drive to Cloud Cross; live in Mammoth Lakes, Calif., and drive to Bishop; or live in Lake Tahoe, Calif., and drive to Sacramento or Reno, Nev. That’s about it. Live high/train low is not possible in places like the U.S. Olympic Training Center in Colorado Springs, which sits at an elevation of 6,200 but is not within a workable driving distance of any place below 4,000 feet.
The hassle of live high/train low is mitigated somewhat by Stray-Gundersen and Levine’s more recent discovery that it is not necessary to perform every workout at lower elevations to reap benefits. In a 2000 study, they found that elite runners improved their 3000-meter times as much when they lived at high altitude, performed all of their moderate-intensity runs at high altitude, and did only three high-intensity runs per week at lower elevation as they did when they lived at high altitude and performed all of their runs at lower elevation.
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Hypoxic sleeping tents represent a technological attempt to achieve the benefits of live high/train low while completely eliminating the need to live and train in different locations, as well as the need to live at high altitude. These devices use generators to create a low oxygen environment within a sleep enclosure that simulates the air at high elevations and thus stimulates the same adaptations in blood chemistry. Numerous studies on the effectiveness of hypoxic sleeping tents on blood chemistry and performance have been conducted. Some have shown benefits while others have not. However, “The bulk of the work on the tents shows that they’re largely ineffective in increasing red cell mass unless you can spend an extraordinary amount of time in them,” Chapman says. “To get a significant improvement in red cell mass, you have to be in the tent 16 hours a day or longer.”
A newer and perhaps better technological solution to the live high/train low problem is exactly the opposite of the hypoxic tent solution. Some elite athletes now live and do all of their training at high altitude, but perform some of their quality workouts indoors while breathing from oxygen tanks. This protocol affords athletes the convenience of living and training in one place, the benefits of spending all day every day at high altitude, and the performance advantage of applying their improved blood chemistry to workouts at simulated sea-level (or even sub-sea-level) elevation, thanks to the oxygen tank.
One of the pioneers of this method is Randy Wilber, a sport physiologist at the Olympic Training Center in Colorado Springs, who oversees training with supplemental oxygen with many resident athletes. In a 2000 study involving cyclists living and training at the OTC, the use of supplemental oxygen over a 21-day period of living and training at high altitude resulted in a 15-second average improvement in a high-intensity cycling test, compared to a two-second improvement in controls who trained without supplemental oxygen.
Among the few triathletes who have made use of this method is three-time Olympian Hunter Kemper. He regularly does treadmill interval runs with supplemental oxygen, and believes he derives great benefits from them. Kemper once tweeted, “My legs love running w/ supplemental O2.”
What is 1.5 percent worth?
According to Robert Chapman, a typical competitive triathlete can expect to improve his Olympic-distance triathlon (non-drafting) bike and run splits by the same 1.5 percent margin by which college runners improved through live high/train low in the study mention above. That translates to a gain of 90 seconds or more for the front-running two-hour racer, or the difference between finishing on the podium or out of the money in many races. (Improvements at the iron distance are likely to be smaller because factors other than aerobic capacity play a greater role in limiting performance.)
Yet even with all that’s at stake at the elite level of the sport, very few triathletes are claiming this free advantage. Boulderites continue to waste their time living and training full-time at moderate altitude. Many elite triathletes continue to get less out of live high/train high altitude camps than they could get out of live high/train low alternatives. And still others are wasting their time (by not spending enough time) sleeping in tents. And a great many more aren’t bothering with any of this stuff at all.
How about you? Would you like to race 1.5 percent faster? Then you need to live high and train low, and you need to do it right. Here’s how.
“The keys to doing it right are making sure you pick the right altitude for living, you pick the right altitude for training, you stay there for the right amount of time, which is a minimum of four weeks, and your iron stores are built up strong before you go up and the whole time you’re there,” says Chapman.
What is the right altitude for living? According to Chapman, the sweet spot is between 6,000 and 8,500 feet. (Anything above 9,000 feet produces negative effects, such as compromised recovery, that counteract the blood benefits.) But the ideal spot within that range differs between individuals. Unfortunately, there’s no way to predict if 6,000 feet won’t be quite high enough for you or if 8,500 will be a little too high. “The only way to know is to actually do it and try to objectively get as much data as you can and subjectively see how you feel,” Chapman says.
What’s the right altitude for training? Studies have shown that 4,200 feet is low enough for most athletes, but some “altitude-sensitive” athletes might need to go a little lower. Of course, supplemental oxygen obviates this issue. With it you can and should go all the way down to the equivalent of sea level, or even lower.
Chapman urges all athletes to have their ferritin levels (an indicator of iron status) checked before and while practicing live high/train low. Altitude exposure is not enough to increase the red blood cell count. The body needs iron as a raw material—more iron than your body normally stores. So it’s necessary to take supplemental iron before and after starting a live high/train low training regimen.
Four weeks of live high/train low are enough to stimulate a 1.5 percent performance improvement, and it’s not clear that additional exposure precipitates additional gains. So you don’t necessarily have to relocate to Flagstaff to practice it. You just need to be able to get four weeks off from work. (Good luck with that.)
The biggest unanswered question regarding live high/train low is how close to races it should cease. In the traditional live high/train high model, it’s important to come down from altitude close to race day, but not too close because, on the one hand, you need time to get used to biking and running at sea level, and on the other hand, you start losing those blood adaptations as soon as you leave the mountain.
But with live high/train low it might not matter so much. Because you’re doing your hardest sessions at sea level already, there’s no need to quit altitude exposure before racing for the sake of adapting the neuromuscular system to sea-level intensity. On the other hand, ceasing to live high several weeks before racing is also potentially workable.
“When you come back [down to sea level], you’re effectively blood doped, so all of your sessions at sea level are that much [faster],” says Chapman. “So even as your extra red blood cells go away, your fitness theoretically would increase because you’re able to hammer that much harder.”
Why isn’t everybody doing this?