“We have recently hypothesized that the optimal approach to altitude training would be to acclimatize to altitude, but train as close to sea level as possible thereby maximizing running speed and maintaining aerobic fitness,” Drs. Jim Stray-Gundersen and Benjamin Levine wrote in a landmark 1992 paper in the International Journal of Sports Medicine.
The pair, who then worked at the University of Texas, were trying to answer the question of whether altitude training was truly beneficial. That same year, for example, they published a paper showing that an equivalent training schedule by groups of elite runners at altitude and at sea level had very similar effects; training at altitude didn’t seem to confer any significant benefit.
“Let’s say you go to Mount Everest,” Stray-Gundersen told FasterSkier in an interview this week. “Your red cell mass will increase, no ands, ifs, or buts about it. It’s really high. But it’s also so high that you can’t train properly for any kind of sport where you need to function at sea level. So one of the questions is, what is that right altitude where you can maintain sea-level conditioning, but high enough so that most of your athletes are going to end up getting a robust increase in red cell mass?”
Stray-Gundersen says in “hypoxic” conditions (when less oxygen than usual is reaching muscle tissues, such as when an athlete is breathing thin, high-altitude air), the human body adapts by producing more of the hormone erythropoietin, which controls the production of oxygen-carrying red blood cells. Training at altitude theoretically confers a benefit because when an athlete returns to sea level, oxygen levels are back to normal, but the blood still has that increased ability to transport it.
What Levine and Stray-Gundersen discovered in that seminal study – which has been cited in peer-reviewed journals almost 150 different times – was an elegant, if not always practical, solution to the problem of how to get an athlete’s blood to carry more oxygen without the potential compromises that come with high-altitude training: live at altitude, but train closer to sea level. There is no one perfect altitude. You need two.
“We had four weeks of living at 8,000 feet and coming down to 4,000 feet,” Stray-Gundersen said of that initial study. “And that was compared to sea level athletes, and then a group of athletes that lived at 8,000 feet and also trained around 8,000 feet. And it’s clear that we had a robust increase in red cell production with living high. But it was only the high-low group that showed performance enhancements, and that’s because they were able to get training in and around the 4,000 foot range.”
The researchers called their technique “Live High, Train Low” (LHTL), and it has been supported in many other studies – and gained enough recognition to fuel the sale of do-it-yourself altitude tents to athletes looking to gain a physiological edge.
“If you get an increase in red cell mass, then you will enjoy an increase in performance,” Stray-Gundersen said. “That’s how blood doping works, and we just developed a method to be able to do that by living up in the mountains.”
Not everyone agrees. While many studies support their conclusions, many don’t – including two papers by a joint Swiss and Danish research group this spring.
Don’t Forget the Placebo
The two papers, which were headed by Drs. Christoph Siebenmann and Carsten Lundby of the University of Zurich and by Dr. Nikolai Nordsborg of the University of Copenhagen, were both based off of a study using elite cyclists to assess LHTL at a training center in the Jura mountains of France.
Unlike the vast majority of researchers who had investigated LHTL, this team used a double-blind design, which is the gold standard for scientific research. It had been difficult to use a double-blind design in studies using natural altitude: athletes knew whether they were living in the mountains or at sea level, and so did researchers.
In the new study, the scientists used artificial rather than natural altitude. By having all of their 16 test subjects sleep in rooms at a training center and then adjusting the oxygen content of each room, they were able to conceal from the athletes whether they were in a “control” room, at the natural altitude of 1,135 meters (about 3700 feet), or in an “altitude” room which simulated 3,000 meters (almost 10,000 feet). Only the lead researcher knew which athletes were assigned where; even the on-the-ground staff did not know, eliminating bias at another level.
The cyclists lived in the treatments for four weeks, during which time they were told to train normally, outside, at the natural 1,135 meters of elevation. They were required to stay in their rooms at least 16 hours per day, or more if they chose.
What Lundy and his colleagues found was that the athletes living the LHTL lifestyle did not increase their red blood cell mass or the erythropoietin levels in their urine, and that group did not see greater improvement in the tests and time trials they performed on stationary bikes and trainers than their control group counterparts.
“I was surprised and frustrated,” Lundby told several news outlets.
But even if the Danes didn’t get the result they were expecting, they have taken their data and run with it.
“Scientifically speaking, altitude training has no effect,” Nordsborg told ScienceNordic, a website covering scientific advances in Nordic countries. “Neither the ability to cycle far or the ability to sprint is improved on average.”
Lundby’s group did see changes in the athletes: for instance, the entire group of 16 averaged a one percent increase in VO2Max, which was marginally significant statistically (the result had a six percent chance of occurring randomly; five percent is the standard cutoff when assessing significance). They also saw a five percent improvement in time trial performance, although this result was not statistically significant.
Based on these improvements, and the fact that the two groups did not differ from one another, the scientists concluded that the placebo effect was at work.
“The study shows that the individual cyclist’s motivation has an incredibly large effect on his performance,” Norsborg told ScienceNordic. “If he expects to perform better because he has slept in air with low oxygen levels, he will perform better – on average 1-2 percent.”
Their assertion was that because all of the subjects believed that the could be in the LHTL treatment, they were more motivated and trained better, or that they had psychologically tricked themselves into believing that they were receiving some benefit.
It’s About Individuals
Stray-Gundersen, who now works with the U.S. Ski Team, isn’t so sure – and frankly, the supposed improvements that the Danes are championing as the placebo effect aren’t so large or significant that they seem to make a big splash.
Instead, Stray-Gundersen asserts, Lundby and his colleagues failed to find a significant effect of LHTL for the same reason that many groups before had failed: it’s hard to do it right.
“I think that maybe the best thing to say about Christian’s study is that they weren’t living in a situation that was sufficient to stimulate erythropoesis,” he said. “However [their treatments] worked, it really wasn’t enough to get an increase in performance or red cell mass. And frankly, if they didn’t get an increase in red cell mass, then we’re not surprised that they didn’t get an increase in performance – so in some ways, their data are consistent with [our] idea.”
He offered several reasons why the study may have found no effect. First of all, it used a small group of athletes – just ten cyclists in the LHTL group and six in the placebo group. Response to altitude is highly individual, and with such a small sample size, it could have been easy to miss an effect.
“Some people, if they go to 2,000 meters and spend four weeks there, they get the increase in red cell mass,” Stray-Gundersen said. “Not all that many people respond there. Other people might have to go to 2,500 meters, or others to 3,000 meters for four weeks… it could have happened that among the subjects that they recruited they didn’t get many who happened to respond to the combination of natural and artificial altitude that they provided.”
This was supported by the papers themselves, which charted the changes in different metrics for individual athletes. With red blood cell mass, for example, six of the LHTL athletes showed an increase after four weeks, while four did not; two of the placebo athletes did, while four did not.
Siebenmann and his colleagues mentioned this in their paper.
“[There is] considerable interindividual variation in the response to LHTL, which is supported further by other studies reporting that the increase in serum EPO during prolonged exposure to high altitude is variable by a factor greater than 40,” the scientists wrote. “It thus appears that in LHTL studies, the presence of an effect on [red blood cell mass] crucially depends on the random composition of the subject groups. This may… explain the lack of an increase in [red blood cell mass] in the present study.”
One thing that everyone agrees on is that more work should be done, with larger groups of athletes – and that the implications of the study include a warning that altitude training works differently for different athletes.
“While some earlier studies indicate that LHTL may stimulate erythropoiesis in some athletes, our results demonstrate that this response is not certain in all subjects, which is probably explained by different individual responses to hypoxia,” Siebenmann and his group wrote.
And there was evidence that the treatment was beginning to work: at the end of four weeks, the LHTL group had a significantly higher reticulocyte count than the control group. Reticulocytes are immature red blood cells that don’t have a nucleus. So although the LHTL athletes didn’t actually have more red blood cells, they were beginning to develop them.
How High, For How Long?
So: there’s no magic number for the amount of elevation needed to produce those red blood cells. And the issue is complicated by research groups using different protocols, particularly with the advent of artificial altitude chambers, where subjects in different studies spend various amounts of time living in the hypoxic conditions.
Even though he said that most people respond with increased erythropoietin production at 3,000 meters, Stray-Gundersen pointed out that his studies have been at natural altitude, where the athletes are living high for 20 or 22 hours per day, rather than at artificial altitude where they spend less time in the hypoxic environment. He didn’t believe that there was any intrinsic difference between the two types of hypoxia, but did suggest that it may be more difficult to find an effect with a smaller proportion of the day spent at altitude.
“Any time you’re using the artificial altitude, you’re in it for less than the 24 hours out of the day,” Stray-Gundersen said. “And the body reacts very quickly. When you go out into sea level again, the body turns off whatever systems it had turned on by being in hypoxia. So what happens is that I think it takes longer, it takes higher, and it maybe takes a longer proportion of the day being in these artificial environments.”
And then there’s the issue of the length of a high-low training camp. Four weeks was the duration of both Levine and Stray-Gundersen’s original study, and of the Danish-Swiss study. But that number came about mostly by chance, Stray-Gundersen said.
“The reason we picked four weeks in the first place is because that was about as long as we thought someone could stay at an altitude camp,” he explained. “If you look at elite athletes, if you send them somewhere for three weeks or more, they end up complaining and they want to go home and all that stuff. Very often the most you can get someone’s attention is for two weeks.”
Two weeks, however, is not enough. An Australian research group has particularly focused on testing LHTL over shorter periods, from ten days to three weeks.
“We conclude that in elite female road cyclists, 12 nights of exposure to normobaric hypoxia (2650 m) is not sufficient to either stimulate reticulocyte production or increase haemoglobin mass,” Dr. Michael Ashenden and his colleagues wrote in a 1999 paper in the European Journal of Applied Physiology. In that same issue, they reported that male athletes spending 23 nights at 3,000 meters did not show an increase in red blood cell mass.
Initially, Stray-Gundersen and Levine weren’t sure if four weeks would be enough. If they hadn’t found significant results, they would have increased their study’s duration to six weeks. But with the wealth of studies showing that shorter periods of LHTL don’t produce results, four weeks seems to be close to ideal.
“You put that all together and you think that four weeks at 2,500 meters for at least 20 out of 24 hours, that’s probably the kind of hypoxic dose that you need to stimulate red cell mass,” Stray-Gundersen said. “There have been a lot of people trying to figure out what the minimal dose is to get away with. Well, that’s sort of the wrong question.”
Overall, the scientist didn’t seem concerned about the press garnered by the Danes’ denial of his method.
“I don’t think that you can say that just because their study didn’t show anything, that you can automatically throw out everything else, or that it obviously doesn’t work and it’s just a placebo effect,” he said. “The literature is full of studies that haven’t shown the kind of responses that we have, and it’s usually because they haven’t been high enough or for long enough. And then there are other studies that have replicated our results when they do live high enough and long enough.”
DIY Altitude Is Tough
One takeaway message from the Lundby’s study: it’s hard to nail down exactly the best way to do LHTL, and doing it right can be difficult.
“Spend the money on other, less complicated training camps,” Lundy suggested to the British newspaper Globe and Mail.
As Stray-Gundersen explained, the use of artificial altitude doesn’t make LHTL any easier. That might serve as a warning to athletes and teams who have invested in altitude tents to try to reap the benefits of the training technique.
“If [a tent] can be used correctly, then it can be effective,” he said. “But I would say that ninety percent of the time, they aren’t used in the right way. Most of the time when athletes buy these things, they don’t get the results that they’re after, for a whole slew of reasons.”
First, he said, many athletes fail to check to see whether the tents are actually maintaining the oxygen levels and saturation they are looking for. Then, they often don’t check their hemoglobin mass before and after they use the tent, so they can’t be certain that they are getting a benefit.
But perhaps more than that, Stray-Gundersen said, it takes a lot of willpower to spend sufficient amounts of time in an altitude tent – both in terms of hours per day, and the long four weeks his group has shown are required to get any sort of physiological benefit.
“A typical experience is that somebody gets a tent, they’re sleeping in it overnight, or even from 7 p.m. to 7 a.m., so they have 12 hours in it – but then they want to, I don’t know, take a trip to visit their parents over a weekend,” Stray-Gundersen said. “And then all of a sudden they’re out of that environment for 48 hours, and that kind of stops the whole process and they go back to the beginning.”
And then there’s psychological stress.
“Even if some of [athletes] are getting better, it’s really hard to spend the majority of your life for a period of time in a big plastic bag,” he laughed, before turning serious. “So there’s a psychological stress or cost to using these things, and to some extent that effect of that stress on your training and performance may be enough to negate whatever benefit you have from an increase in hemoglobin mass.”
For athletes looking to do LHTL on their own, Stray-Gundersen had the same warnings that he did for his fellow researchers. Using natural altitude – living in the mountains – is probably a more sure-fire way to gain red blood cells. And if you use artificial altitude? Be careful.
“In most athletes hands, they don’t have sufficient help or advice, and I think they mostly end up being ineffective,” Stray-Gundersen concluded.