Altitude Training Mask

Do Altitude Training Masks Work for Endurance Athletes?

By now you have no doubt seen bros running around, lifting weights, or even riding around at sea level or moderate elevations with altitude training masks. The idea is to simulate the hypoxic condition of exercising at altitude (about 5,000 feet above sea level and higher). With some products, there’s also a component of ‘resisted breathing’, where you have to physically work harder to inhale and exhale. Cyclists, triathletes, and runners want to know if a altitude mask will make them faster, so let’s take a look at the science.

How an Altitude Training Mask Functions

Many of the masks available on the market simply restrict your breathing so you can’t pull air into your lungs as fast as normal. When you exercise with one you basically get out of breath sooner, at a lower exercise intensity level, than normal. You’ll also accumulate more CO2 in your blood. But the composition of the air you’re breathing is the exact same as it was without the mask. You’re only getting less oxygen because you’re getting less air.

Exposure to true altitude is different. Here in Colorado Springs at 6200 feet above sea level, the percentage of oxygen in the air is the same as it is at sea level (about 21%). But since the air pressure is lower at altitude those oxygen molecules are further apart, so there are fewer of them in a lungful of air. You’re breathing in the same volume of air, there are just fewer molecules of oxygen in it. Altitude tents and altitude rooms like the High Altitude Training Center at the US Olympic Training Center in Colorado Springs work in a similar way. They remove oxygen from the air you’re breathing so that when you draw in a full breath there’s simply less oxygen in that volume of air.

The point is, an altitude training mask is not simulating the same type of hypoxia athletes experience either living or training at higher elevations, and that seems to be a crucial difference.

The Fatal Flaws of Altitude Masks for Endurance Athletes

The short answer to the question of whether you should invest in an altitude training mask is: No. But, as with so many things in sports science, there’s more to the story because there can be benefits to exercising in a hypoxic environment, they’re just not the ones you normally associate with altitude training. First, here’s why you don’t need the mask:

Restricting Your Breathing Ruins Your Workout

As an endurance athlete, your goal is to maximize your ability to deliver oxygen to working muscles. The more oxygen you can inhale and deliver per minute, the more muscular work you can perform. When you restrict your breathing with a mask, you lose power and go slower. You’re stressing your ability to breathe, not your ability to do work. To improve fitness for endurance sports you need to accumulate enough workload to create a training stimulus, and you can’t work as hard when your breathing is restricted. Ironically, the mask makes your workout difficult and exhausting, but ultimately less effective.

Strengthening Breathing Muscles Doesn’t Improve Athletic Performance

Breathing against resistance in training doesn’t result in an increase in the amount of oxygen you can take in per minute when you remove the resistance. In other words, the strength of your intercostal muscles and diaphragm aren’t limiting factors in your ability to fill your lungs. When people report feeling like they can breathe deeper, it is likely because breathing deeply or forcefully has helped the muscles loosen up and increased the mobility of your ribs. You’ll notice the same thing if you have to take a few weeks off from exercise; after a workout or two you feel like you can take bigger breaths because your chest has loosened up.

Even Elite Athletes at Altitude Don’t Want To Train at Altitude

Athletes who live at altitude acclimate to the elevation by developing more red blood cells. That means they can train effectively at that altitude, but their power still declines when they go up into the mountains outside of town. The bigger benefit to living at altitude is the ability to go down to lower elevations for training camps where elite athletes can take advantage of increased oxygen carrying capacity in an environment where there’s more oxygen. They don’t do the opposite. They don’t live at 6,000 feet and go up to the top of mountain at 12,000 feet to do their intervals. In specialized cases we also employ supplemental oxygen training for athletes living and training at altitude. The High Altitude Training Center (HATC) at the Olympic Training Center is more often used to simulate sea level conditions than high altitude conditions. By adding oxygen athletes can achieve sea level power outputs in training, or recover in sea level conditions, while living at altitude.

Even If the Idea Was Good, the Exposure Is Too Short

Part of the reason the traditional “Live High, Train Low” method of altitude training says “live high” is because the phrase indicates how much time you need to be exposed to altitude for it to yield a positive training adaptation. Restricting oxygen for the short duration of a workout isn’t enough of a stimulus to lead to the training adaptations you’re after from altitude.

When High Altitude/Hypoxic Training Makes Sense

While the stand-alone altitude masks that operate by restricting breathing don’t improve endurance performance, there are some ways that hypoxic training can be useful.

Pacing and Perception Training

CTS Athlete Rebecca Rusch (3x World Champion, 4x Leadville 100 Champion, 3x Dirty Kanza 200 Champion) is preparing for an expedition to hike up and mountain bike down Kilimanjaro (see video below). She recently spent 3 days walking on a treadmill wearing a 40lb weight vest in the HATC, not to improve her fitness, but to determine the best pacing strategy for carrying 40lbs of gear up to 19,000 feet above sea level. When she went too fast, like accelerating from 2.2 to 2.5mph on a 10% grade at 13,000 feet, her oxygen saturation would plummet and her heart rate would spike. This was coupled with perceptions of tingly fingers and pressure behind her eyes. Together, the speed, heart rate and perception data gives her more knowledge about how to gauge her efforts. Similarly, athletes preparing for Leadville or other high-altitude events benefit from training at altitude to gain an understanding of how hard they can go and how their power and sustainable pace will be affected. Even exposure to altitude, including during short visits, can help acclimatization somewhat. With short visits you don’t have time to increase red blood cell mass, but you may stimulate ventilatory changes, which can help. This is part of the reason mountaineers go up to higher base camps and come back down when they are on their way to extremely high summits.

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Intermittent Hypoxic Training

There’s another version of altitude training that could be promising for some athletes, called intermittent hypoxic training (IHT). With this method athletes perform efforts of 3-5 minutes while breathing a low-oxygen air mixture (not restricted breathing) equivalent to high altitude (11,000 feet, for example). Recovery periods between sprints are in normoxic conditions. The idea is to stimulate acclimatization to high altitude, like ventilatory response, rather than improving fitness. But again, even if a sea-level athlete wanted to try this they would need equipment like the Hypoxico Altitude Trainer Box that lowers oxygen content of inspired air, not a breathing mask that restricts total airflow.

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Chris Carmichael
CEO/Head Coach of CTS
with Jim Rutberg, CTS Pro Coach


Related Articles

Is Hyperoxic Training the Next Big Thing

What Time-Crunched Athletes Need to Know About Altitude Training

Understanding the Challenges of High-Altitude Racing at the Leadville 100 and USA Pro Cycling Challenge


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Comments 37


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  6. Maybe it was a placebo effect, but wearing the mask greatly prepared me for my 9 month Afghanistan deployment in 2013. I also had a much improved pt score when wearing for working out.

    Every tool has its purpose. Y’all know this

  7. The issue to me with the article is that it is mainly speculation on why restricting breathing would not work.
    The basis the masks claim to work is to reduce oxygen intake.
    Do they reduce or not? If they reduce why would not they work as well as, if not altitude training, then Intermittent Hypoxic Training.
    Basically if you restrict your breathing the mix in your lungs will have less O2 and more CO2, so very similar effect to the latter.
    It should be pretty easy to test if you have equipment, so no need for speculation.

    Other than that, are these masks needed? Perhaps one could just inhale at lower rate instead.

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  9. I know this an old article, but I’m hoping you and others read this.

    I’m signed up for the Beast in August Breckinridge for 2018. I live in Florida and did the Sprint in Florida (April) and the Super in Fayetteville NC (May). All these were a challenge but I completed them. I continue to train each week.

    I’m a little concerned about this challenge. I’m signed up with some friends who have been with me for each challenge and we are all from Florida. My daughter who is 14 will be joining us and she has completed the same races with us. My concern is altitude and then the hills for all of us. Curious how many young people to the beast at this level. Not sure what advice you can give us, but I’ve passed along this article.

    My daughter and I have been to CO. We’ve been to Rocky Mountain National Park and stayed in the park. No altitude issues, but wasn’t doing a spartan. Lol. Been on top of Pikes Peak and we both felt light headed at the top. Our water and snacks helped us, but going back down helped us even more. It will be different understanding what our bodies are telling us when trying to perform.

    Any advice would be appreciated.

    Thank you.

  10. What do you feel about training mask 3.0
    I just see a review here

    Looks interesting

  11. I used the mask and when used intermittently throughout a workout it actually allows you to push farther into your workouts without being as tired as you would if training without the mask. It’s a mental training device but also i have seen that my muscles are less stressed and I can finish my routine running workouts without the heaviness I would get in my legs when not training with the mask

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  16. I got a question, I live in a country that is +5k feet high (Ecuador)… So I was wondering if it was useless to buy on of these masks?

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  18. I’m a little confused by this article. Maybe it didn’t explain in enough detail to match what I understand about hypoxic training. Or maybe I’m not getting it. If restricting your breathing makes you out of breath, that feeling of being out of breath is caused by CO2 build up in your blood stream. The CO2 increase is either through insufficient O2 or by reducing expiration/ventilation rate so CO2 production is greater than CO2 expired. So the question is, does the training mask reduce blood O2 saturation level or is it simply reducing CO2 expiration rate?Intuitively, I would suspect a little of both. So the next question is, if O2 saturation is reduced, is it enough to illicit a beneficial response? The article says there is no benefit and I don’t necessarily disagree, but it does not mention O2 saturation, yet it implies that being out of breath is via insufficient O2. Some of these points need further clarification.

    1. Post

      You make a good point, and I don’t have all the answers to your queries. As you alluded to, breathing rate is governed by the amount of CO2 in the blood. I suspect you’re right that blood levels of CO2 rise with restricted breathing through a mask. I have also seen studies saying they reduce oxygen saturation by causing the wearer to rebreathe exhaled CO2 trapped in the mask, thereby reducing the oxygen content in inspired air.

      As to whether there’s physiological benefit from this scenario, I think the problems are still the short duration of the exposure (too short to stimulate blood cell production) and the reduction in training workload. Even if the mask were to induce hypoxemia, how long does it take for hypoxemia to be induced (you only absorb about 27% of the oxygen you inhale under normal conditions anyway) and is the total exposure time long enough to stimulate red blood cell production? The even bigger question is whether an athlete would stimulate more positive fitness adaptations through high-quality training (intervals not hindered by hypoxemia) or through short bouts of hypoxemia? The coaching staff here believes the former. – Jim Rutberg, CTS Coach

    2. I have a scenario:
      I’m in the military and will be leaving to take an APFT (consisting of pushups, sit ups and a run) at a very high elevation compared to where I live. I want to do my best but I have seen many people fail because the test here is not the same as taking the test at a high elevation. I am thinking about buying a mask to train for primarily the run. Do you think this will be helpful?

  19. What about the book -Breathe Strong, Perform Better- author Alison McConnell. She designed the “Breathe Right” trainer to improve the strength of the Intercostial and diaphragm muscles.
    Last summer I read an article in Bicycle Mag. concerning breathing, Inhale long, slow and deep, exhale long, slow and empty lung. This gives O2 and Co2 to pass through the membranes and also keeps rider calmer while working hard. It worked for me, I had been panting breathing, I changed to long and slow using belly breathing, I got faster and it took longer for HR to increase and I was calmer while going all out.

    1. i think this mask would work in regards to the mental side of things, if you can push yourself to the edge wearing a mask, you could potentially push yourself alot further without it, therefore there is some benefit, everyone focuses on negatives these days

  20. Donating plasma increases EPO levels even in the absence of exercise. When I donated plasma every month, I had a steady hematocrit of 45. I’m too old to get paid for it anymore, but maybe I should go back to doing it. There’s a temporary decrease in performance until you replace the plasma, but it’s quick to replace since all your RBCs are still there. I shouldn’t post a link, but you can google “ERYTHROPOIETIN (EPO) LEVELS INCREASE DURING HYPOXIC EXERCISE AND PLASMA VOLUME DEPLETION”

    Back to the subject of altitude training, I’ve noticed that when I ascend from sea level to 10,000 in one day, my performance is poor. But if I just spend one night there, my performance the next day is much better. I think this CTS article explains at least some of the mechanism for that, which is great because I’ve always wondered why. BTW, doing jumping jacks at 10,000′ easily brings my blood O2 levels down to 93% or below, by pulse oxymeter, which I think is the level at which increased production of EPO starts. Of course you have to stay up high or those baby RBCs get scavenged out a few days after returning to low altitude.

  21. ” They remove oxygen from the air you’re breathing so that when you draw in a full breath there’s simply less oxygen in that volume of air.” That is incorrect….the altitude chamber removes AIR from the chamber not just oxygen. There is less nitrogen, argon, hydrogen and everything else in the chamber. The pressure is lower than outside the chamber, but the percentage of indivual gasses in the air you are breathing remain constant. Put another way, the partial pressure of all the gasses is reduced. Removing oxygen alone would be much easier, you could simply pump nitrogen into the room…this is done with tires to supposedly decrease the rate of loss of pressure through a tire wall since nitrogen atoms are larger (albeit very slightly) than oxygen. That doesn’t really work on a practical basis however.

    1. Not really incorrect. More succinctly, removing air and thus lowering the pressure results in less O2 molecules per unit volume.

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  23. Thank you for publishing such a common-sense article. I never understood the logic of how something openly marketed to strengthen inspiratory muscles could increase RBCs in the blood, thus improving oxygen carrying capacity.

    It’s pretty disgusting how “tools” like these are now being pushed out to the masses, who in turn are literally paying to impede their own training.

  24. I have a tenth grader and the kids goimg out for track and football all have these. I am concerned about ill effects on kids. We have such high requirements for drug safety in america why don’t these profit monger snake oil salesmen have to valdate product safety. Robbing my kids brain of oxygen seems bass ackwards.

  25. Hi, my previous comment on Jan 31st on the training mask article is still awaiting moderation. Is there a way you can do this soon or let me know of anything that I should not have included so I’ll know better next time. Thanks

  26. This is an interesting article as it addresses one of several products out there that appear to be filling the void of ignorance in the mechanism and benefits of altitude training. While blooding doping and the use of EPO are banned in sports, altitude training, the use of reduced oxygen tents, Altolab type breathing devices and now these training masks are not banned. This is due mainly to the logistics of implementing the ban. How do you stop athletes from living at altitude etc? Using the fact that there are documented benefits of training at altitude under certain competition conditions, then these other devices claim similar benefits by claiming to simulate similar conditions. While this may appear to be a logical conclusion on the surface, logical enough for these products to achieve the sales they do, further analysis of the underlying physiological mechanism begs the question, do they really work? It is pretty obvious that if any of these devices raises blood hematocrit levels above what is normal for the individual, then the device obviously works. However, some of these devices claim to work without such a measurable physiological change. The Altolab device, which reduces oxygen levels by recycling expired air through a CO2 scrubber, claims improved performance without any measurable change in hematocrit. One asks whether there are other mechanisms in oxygen transport or CO2 buffering etc that are improved which can result in performance improvement. I don’t know the answer to this question. Also, the mask, as pointed out in the article, has even less of a logical reason for performance improvement. One of the things the Altolab device does is to provide a measurable reduction in blood O2, usually in the range of 70% to 90% saturation given a normal level of around 98% for most healthy individuals. So, one thing that could be done with the mask is to see if it reduces blood O2 level. Something that can be simply checked with a device that clips onto your finger. Swimmers train under similar conditions to wearing a mask in that their breathing opportunity is limited and they learn how to perform under these conditions. For runners, cyclists etc, no such limitation exists so one rightly wonders if any benefit is obtained from this device. That is, is the feeling of being able to breath properly after removing the restriction conning the user into thinking there is some benefit. The mask appears to raise CO2 levels but is this due to the extra effort of breathing or due to a reduced breathing rate and does it result in lower blood O2 levels? Answers to these questions should provide additional evidence to their value as a training aid. My 2 cents.

  27. You can donate blood, train at 80% intensity and produce the same benefits as going to altitude. Takes about 3 weeks to recover to a higher “normal”

  28. At altitude, it’s not only the fact that their is less O2,, but also that the pressure of the O2 is less. Less pressure means less makes it into the blood. The lower density and lower pressure conspire together to reduce the amount of O2 taken up by the blood.

  29. That was great, thanks, so many gimics and false information, that athletes. Want the edge, but are perhaps doing damage and even taking 2 steps back. Leave it to and Trust science to explain Everything in our physical world. We need to do our homework first B4 jumping On a band wagon of false information, and gimics. Thanks again for clarifying. I enjoyed the video as well

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