Altitude training used to be reserved for pro athletes and Olympians (Kristian Blummenfelt, anyone?). You’d hear rumors of WorldTour pros disappearing into the mountains, but it was all very niche.
Now? Altitude training is practically required for endurance athletes. Head to Sierra Nevada, Mount Teide, or Font Romeu in the spring, and you’ll see entire cycling teams camping out at 2,000+ meters.
But what’s actually happening in the body at those altitudes—and does it work?
In a recent Nduranz podcast, we sat down with Dr. Tadej Debevec to talk the science behind altitude training. Dr. Debevec is a professor at the University of Ljubljana who did his PhD on altitude training, and has also studied everything from thermoregulatory systems to artificial gravity for spaceflight. (Yes, really.) He's also a mountaineer and mountain guide who loves getting out into extreme environments.
Let’s get into the science.
What Happens to the Body at High Altitudes?
First, a quick science lesson.
As you go into high altitudes, barometric pressure drops. The percentage of oxygen in the air remains roughly the same, but the overall amount of oxygen in each breath is lower.
In simple terms, this means less oxygen is available for the body at high elevations. The body responds by trying to deliver more oxygen to the systems:
- Heart rate rises
- Breathing rate increases
- Cardiac output elevates
- Fatigue hits faster than expected
Since oxygen is required for all energy and muscular systems, it has a huge effect on performance. We can see this in the mountain stages of Grand Tours—the power output of the front group suddenly starts hemorrhaging when they go over 2,000 meters.
Doctors in the Death Zone
In 2007, a BBC special called Doctors in the Death Zone followed a team of doctors who conducted medical tests—using their own bodies as test subjects—as they climbed Everest. They were exhausted even at 50 watts and could barely get to 90 watts. It shows just how much you suffer when you go high up in altitude.
Why Altitude Training Improves Endurance Performance
With sustained exposure to high altitudes, the body begins to adapt—most notably by producing more erythropoietin (EPO), which stimulates red blood cell production.
More red blood cells = more oxygen-carrying capacity = better endurance.
Other benefits of altitude training may include:
- Better respiratory efficiency
- Improved lactate buffering
- Enhanced oxygen economy
What the Science Says About Altitude Training
We know that long-term exposure to high altitudes causes measurable adaptations. Andean highlanders and Sherpas of Nepal, for example, show significantly higher hemoglobin levels and greater oxygen transport capacity.
But when it comes to using altitude training to boost athletic performance, the science isn't as clear for these reasons.
1. Study Conditions Often Don’t Match Real-Life Competition
Much of the existing research was done at extreme elevations—above 3,000 or even 4,000 meters. Yet most endurance races don’t take place above 2,500 meters (which physiologists consider only "moderate to high altitude"). That raises questions about whether the findings translate to racing conditions.
2. Results Vary Widely Between Studies
Altitude training is hard to study. Differences in altitude, duration, training load, and measurement methods make it difficult to compare results—which is why studies often have inconsistent findings.
3. Not All Athletes Respond the Same Way
Some athletes respond well to altitude training, with improvements in hemoglobin levels after altitude exposure. Others don't respond at all.
Dr. Debevec says it is hard to pinpoint the reasons behind these different responses, but it likely comes down to a combination of factors such as training status, recovery, and overall health. In short, what works for one athlete might not work for another.
Is Altitude Training Worth It?
Despite the gaps in research, both Dr. Podlogar and Dr. Debevec say that altitude training is mandatory if you have a race at high altitudes.
“If you're not exposed to altitude whatsoever and you just suddenly come above 2,000 meters, you will suffer.” – Dr. Podlogar
“When you know you'll be competing at higher altitudes, such as a competition with a summit stage that finishes at 2,400 or something, it would be really unwise not to pre-prepare for altitude.” – Dr. Debevec
But remember, altitude training isn’t a replacement for solid training—it’s an extra stimulus. Dr. Debevec warns that if your base training work isn’t dialed in, altitude training won’t save you. However, when layered on top of a good foundation, it can offer performance benefits for endurance athletes.
How to Do Altitude Training Right
1. Understand the Risks of Altitude Training
Before you try altitude training, you need to be aware of the risks. If not done carefully, it can actually harm performance:
- Poor Recovery: It’s harder to sleep at high altitudes, which can hinder recovery. Issues like mountain sickness can also harm well-being. Dr. Debevec recommends staying below 2,400 m to avoid these problems.
- Cumulative Stress on the Body: Trying to maintain the same training at high altitudes will put additional stress on the body, increasing the risk of overreaching.
- Disrupted Training: Training at higher altitudes is more difficult. If you’re too tired, you won’t train effectively—and your goals may suffer.
2. Commit Enough Time to See Results
Dr. Debevec says that altitude training requires at least 250 hours to produce adaptations. That means:
- ~10 days of continuous altitude exposure
- ~18–21 days of exposure just while sleeping
3. Choose the Right Method of Altitude Training
There are many methods of altitude training, but not all are created equal.
Live High, Train Low (LHTL)
Dr. Debevec says LHTL is the best method for endurance athletes. Athletes live or sleep at high altitudes (around 2,000–2,500 meters) to trigger red blood cell production, but train lower to maintain normal intensity and mechanical load.
Live High, Train High (LHTH)
A traditional model where athletes both live and train at altitude. It’s easier logistically and may provide benefits, but training quality—especially high-intensity sessions—often suffers. Dr. Debevec recommends LHTL instead.
Live Low, Train High (LLTH)
This method involves living at sea level but doing workouts at altitude. Dr. Debevec says the science is unclear and that high elevations may hurt performance. He does not recommend this method.
What methods are not worth it? Some methods—like repeated sprint training in hypoxia, intermittent hypoxic exposure (IHE), and intermittent hypoxic training (IHT)—may have niche uses such as muscular rehabilitation. But according to Dr. Debevec, they are not useful for improving endurance performance.
4. Consider an Altitude Tent or Chamber
Can’t live on a mountain? Altitude tents and chambers (hypoxia rooms) simulate altitude by reducing oxygen concentration.
According to Dr. Debevec, both options can trigger adaptations. Chambers may be slightly more effective due to pressure differences—and they’re easier to personalize to each athlete.
“Altitude tents and chambers can even be better than mountains. If you send an entire team up a mountain, the altitude might be too much or too little for certain athletes—but there’s nothing you can do to change it. By contrast, you can adjust the settings on tents and chambers to personalize training.” – Dr. Debevec
However, sleeping in a tent can be uncomfortable and affect recovery. Dr. Debevec recommends chambers over tents for this reason.
5. Check Your Iron Before You Go
Altitude training stimulates red blood cell production—but only if your iron levels are sufficient:
- Get a ferritin blood test at least 3 weeks in advance
- Aim for ferritin >60–70 µg/L
- If low, supplement with 100 mg of iron daily (or follow your nutritionist’s advice)
- Female athletes: pay extra attention—low iron is more common and more impactful
6. Start Healthy
Altitude training is a significant physiological stressor. If you begin training while already sick, fatigued, or overreached, the added strain of altitude can seriously impair your adaptation and performance.
You must be in good health and well-rested before starting altitude training to ensure your body can handle the extra demands more effectively. Prioritize recovery, address any lingering illnesses, and ensure your nutrition and sleep quality are optimal.
7. Don’t Go Hard Right Away
Your body needs time to adjust. Dr. Debevec recommends:
- Ease in during the first 3–4 days
- Monitor heart rate, RPE, and sleep quality
- Use a pulse oximeter or HRV tracking if possible
- If you feel terrible—adjust the plan
8. Monitor Macros
According to Dr. Podlogar, altitude doesn’t greatly affect carb oxidation—except at extreme elevations. But it does increase energy needs while suppressing appetite. This combo can lead to an energy deficit that harms recovery and performance. Track your macronutrient intake carefully during camp.
9. Don’t Try Weight Loss at Altitude
Some athletes try to lose weight during altitude camp. Both Dr. Podlogar and Dr. Debevec advise against it. Cutting weight adds more stress, reduces recovery, and can undo the benefits of altitude training. It’s not worth the risk.
Want to learn more about altitude training? Listen to the full podcast episode with Dr. Debevec.