I recently spent three months in the Andes mountains training for my first ultra marathon. I had my base in the city of Cusco, Peru, and explored the mountains and trails in and around the Sacred Valley of the Incas. It was a tremendous experience. I’ve seen some of the most beautiful and dramatical mountains the world has to offer, and while doing this I’ve gotten to know my body really well after studying how I’ve reacted to training in 3500m-5600m altitude. This article will break down the principles of high altitude training, how I subjectively felt before, during and after this three months long training camp.

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Why athletes experiment with high altitude training

Short explanation: The atmospheric pressure drops the higher you get, which results in a lower molecular density. This means the amount of oxygen available at high altitude is lower than at sea level. Since oxygen is one of our bodies main fuels, it causes a biological reaction where we produce more red blood cells to level up our capacity to take up the oxygen available. This increases your maximal oxygen uptake, aka “VO2 max”. Combining this with possibly traveling down to sea level for an endurance race will give you an edge you couldn’t possibly get if you trained at sea level.

How long and how high?

Top athletes normally do high altitude training camps for about four weeks. The length of their camps usually aren’t very long due to their packed schedule of other kinds of training, races and other obligations as a professional athlete. Studies have shown that doing this between 2100-2500m altitude is the sweet spot when it comes to performing better at sea sea level after four weeks. But they also do it in this specific altitude because they don’t have to spend an unnecessary amount of time acclimatising before they can start training. For an elite athlete every day not training is a big deal, so having to wait a couple of weeks to be able to train is a deal-breaker. Here are some more reasons for not going too high when experimenting with high altitude training:

  • The higher you go the longer the recovery between workouts will be
  • The production of red blood cells can actually work against the intention as it results in a blood thickness which your heart will struggle to deliver around the body
  • Your immune system gets weakened
  • Loss of appetite
  • Your body will start consuming the muscles in your body for energy when you go over 5000m
  • Altitude sickness may occur, which will kick an athlete out of the game for a while both because of the illness as well as the fact that you need to travel down to sea level to recover.

Why is 2100-2500m the perfect altitude?

  • It doesn’t slow down an athlete’s recovery notably
  • They can keep almost the same intensity they’re used to at sea level
  • They won’t have to spend too long acclimatising before they can start training at altitude
  • It’s high enough to give the athletes what they want out of high altitude training; A higher amount of red blood cells and an increase in their VO2 ma without sacrificing any of the negatives listed further up in the article.

In my case as a hobby mountain runner and a traveler I had no reason to hurry down from the mountains. Having to wait three weeks for my body to adapt wasn’t a big deal for me. I had nothing to loose. I spent my first two weeks in Cusco getting to know the area of my AirBnb and doing touristy things. If my body recovered really slow from my workouts it didn’t bother me too much. I would just take a day off doing yoga or something else. I was there for 3 months, so I had lots of time to experiment with the altitude compared to most other athletes. I was sleeping at 3600m and trained at 4-5000m, which brings me to the next topic.

High altitude training principles

There are two main schools of high altitude training:

  1. Train high and recover high
  2. Train high and recover low

Train high and recover high

The most popular one, which most top athletes have started using is the “train low and recover high” method, which by definition isn’t high altitude training. I would rather call it “high altitude sleeping”. The theory behind this method is that acclimatising to high altitude during your sleep whilst training at sea level will boost your efficiency at sea level. It will most definitely boost your efficiency at high altitude as well, but few major sporting events tend to happen in high altitude. Since traveling to high altitudes (>2500m) to sleep and traveling down to sea level to train every day can be a lot of hassle, products like high altitude tents have been invented. This way athletes can sleep in a tent with a controllable atmospheric pressure to mimic high altitude.

Train high and recover high

Training high and recovering high is the other method, which is also the one I did during my stay in Peru. It’s pretty self explanatory; you’re exposed to low atmospheric pressure constantly. You train and recover in altitude.

Isn’t this doping?

As mentioned above, the results of high altitude exposure is an increase in red blood cells. This is also the result of drugs such as EPO and also “blood doping” where you take blood out of your body and insert it back in after you’ve produced more blood. So yes, if you want to look at it as doping, be my guest. But at least you can do it guilt free and without any needles and blood bags in your hotel room. It’s also not an instant and guaranteed effect. Everyone experiences a training camp in high altitude differently. It also takes you out of your controlled training environment and sets you back with your training for an unknown time depending on how high you go and how your body deals with adaptation. So doing high altitude training is not the same as the instant effects as doping. It actually sets you back and you’re not guaranteed a positive effect in your athletic performance. After considering the setbacks and environmental change you might actually be better off staying at home doing what you’re used to.

How my body reacted to the altitude

One of the first things I remember after arriving in Cusco was that I had to catch my breath while eating a banana. Breathing with my nose while stuffing my face wasn’t enough. I had to rethink the way I chewed my food. I remember looking at the mountains while chewing the banana and thinking: “Are you expecting me to run when I can’t even eat a banana?”.

I went for my first walk/hike after a couple of days. It was a 15km hike with 500m climb, but I went slow and didn’t push it. But I still ended up with a major head ache afterwards and had to chill the day after to recover. I slowly started to speed up my hikes, and after around three weeks I had my first real run I was happy with. It pretty much went up from then on. I increased length, duration and elevation climb in my runs, and after around 6 weeks I had found my regular route which consisted of 950m elevation climb for 16km.

At the end of my stay in Cusco (after having been there for about 9 weeks), I still didn’t feel that I had fully adapted to the altitude. Hill sprints were still extremely brutal, and I still felt a major difference than what I was used to at sea level.

Main takeaways

1. Running in high altitude points out your weaknesses

Since you’re so fragile with the lack of oxygen you’ll quickly find out the weaknesses in your running game. My main weakness was my cadence and stride length. Burning an unnecessary amount of energy on long strides in altitude really exposed how big of a waste it is. I was used to doing a cadence of < 80, but I had to increased it to >80 as well as shorten my stride length. I’ve since kept it up and I’m able to comfortably run at a cadence of 84.

2. Running at a steady pace will benefit you on longer runs

Again, because of the impact the altitude has on your breath, you’ll quickly learn that doing that improvised sprint to the top of the hill isn’t worth it if you want to last for a long run. The smallest extra constraints will set you out for a couple of minutes and take you from an aerobic to an anaerobic state, which will screw up for the rest of your run.

3. Forget trying to stay in a “hr zone”

Even though my heart rate monitor wasn’t working during my stay in Cusco, I’m very ware of my heart rate and which zone I’m in. I quickly came to learn that slow runs wasn’t synonymous with low hr runs. I was constantly battling myself not to fall in to the black hole training category, even though I know I was very guilty of it most of the time. If you want to keep your hr low, go for a hike.

4. Want to do an anaerobic session? Be my guest.

It took me a long while before I felt comfortable going out for a run with the aim at tapping in to zone 5. This was because I felt guilty of already tapping in to this involuntarily almost every run because of the altitude. But the times I did do pure anaerobic sessions I really pushed it, and I can tell you that pushing your anaerobic threshold at >4000m altitude is a hell of an experience. I mostly did 30-60s sprints with full recoveries and the recovery period varied from 90s-4minutes(!). I never did anything longer than this because it simply wasn’t doable.

5. Lactic acid

One thing I’ve missed (surprisingly) during my stay in the altitude was the burning sensation of lactate in my body. It turned out that my body would rather prefer to gasp for air and slow down rather than producing lactate for energy. I know that the lack of oxygen and brain fog makes you take weird decisions such as slowing down when you’re out of breath, and I was well aware of this during my anaerobic runs. Therefore I tried to push the limits to see if I could manipulate these instincts. It turns out this is really hard and that the need of oxygen is superior to what your objective mind wants. My anaerobic hill sprint sessions turned in to a breathing exercise from hell rather than an acid party, which you would probably expect it to be.

6. Runner’s high is a thing

I’ve experienced runner’s high a lot in my lifetime, and I can tell you that running in high altitude will increase yout chances of this experiencing by many percent. I’m not sure if it was the light headedness due to the lack of oxygen or just the euphoria of running in the stunning nature, but I experienced it on pretty much all of my runs.

My experience of runner’s high is the feeling of a slight brain fog while being 100% aware of it, and at the same time being very present and in the moment. It’s like as if you’re dreaming whilst being fully aware that you’re dreaming. My suspicion is that this lack of oxygen to the brain acted like a catalyst of the runner’s high, and I was able to tap in to this state of mind faster than I was used to from training at sea level due to the lack of oxygen.

7. “How did it feel to get back to sea level?”

My main goal while training in Peru was the Ultrafiord 50km race in Puerto Natales, Chile in April. Unfortunately I went down with a bad case of stomach flue when I got there, so couldn’t race. But I got a couple of training runs before I got sick. And now that I’m writing this article I’m back in Norway, and it’s been 2 months since I left Peru, and I can still feel the effects of the high altitude training. So how do I notice the effects?

  1. My aerob capacity has increased dramatically. I’m blazing over hills without having to slow down at the top to catch my breath. It’s an incredible feeling. Is this because of the altitude training, or simply just because I had a lot of quality training in Peru? I don’t know. If those mountains were at a lower altitude I might even have gotten a better effect.
  2. My confidence after training in high altitude for long distances makes me feel unstoppable. “How can any training session or race beat what I went through in Peru?” is what I tell myself every day.


The effects of high altitude training over a longer period of time is a subject which hasn’t been fully researched yet. But my subjective opinion is that my endurance game benefitted a lot from my 10 weeks of running in the Andes mountains. If it was because of the altitude or just that the conditions for training there were as good as they were will still remain a mystery.

Before you share or comment on this article, please enjoy some photos and videos of my experience in Peru.