I think the benefits of altitude training are well known, but a popular trend (especially in Mixed Martial Arts (MMA)) is simulating altitude training with a gas mask or other device to restrict oxygen.

I always thought the altitude training was an immersion thing, not just during the actual training, but a cumulative effect of 24/7 decreased oxygen. Any science to back up the gas mask training idea?

One example site here.

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    No real knowledge on the subject, but out of my belly, I'd assume that you can mostly train CO2 tolerance that way (larger dead space), though you might also somewhat increase your lung capacity and strengthen your diaphragm, since there is a much higher respiratory resistance. I wouldn't bet my right arm that it's really healthy, though (emphysema comes to mind, since you practically simulate a quite severe COPD). For polycythaemia, which is normally what one does altitude training for, I'd not expect any effect from this, unless you wear it almost all day.
    – dm.skt
    Commented Mar 13, 2011 at 22:56
  • I had always understood that altitude acclimatization was a response to the lower air pressure, rather than difficulty breathing, per-se. As far as I know, people with allergies and Asthma (or Emphysema, for that matter) don't generally develop additional red blood cells, which definitely happens when living at altitude. It's possible that a mask that preferentially absorbed oxygen would trigger the same response, but I assume the sort of gas mask device you're talking about merely increases breathing effort. Commented Mar 17, 2011 at 18:12

2 Answers 2


Okay, looking at this site and reading:

helps condition the lungs by creating pulmonary resistance, your diaphragm is strengthened, surface area and elasticity in the alveoli is increased.

Basically all this does is make it harder for you to breathe. Thereby making you train to a certain level of exertion under an already exerted condition (some credence to the endurance claim, but muscular endurance, not aerobic endurance). This in no way simulates high altitude because of the pressure. The lower air pressure is a result of there being less air all around you (not just in the lungs).

The effect of this device would be to simulate asthma or some other bronchial restriction, NOT altitude. You are correct, altitude training requires actually living at altitude and acclimating to it. Although, at altitude, a mask like this would possibly give the strengthening claim some additional benefit.

A researcher at Columbia University says:

Because of the inconclusive nature of the studies done so far, the answer to that question is still up in the air. What researchers do know is that constant exposure to low levels of oxygen can do more harm than good to the body. It can cause chronic stress, detraining, and edema (fluid buildup in the lungs and brain). In some cases, blood can thicken too much, raising the risk of death due to blood clotting.

I would suspect that the lack of data is because the research itself may involve greater risks than most researchers would ethically want to take. And those that have done "studies" are the same ones selling the masks, with an obvious conflict of interest as well as not performing actual research, but rather appealing to a "this should make sense to a layperson" strategy of marketing.


BMJ. 1998 October 17; 317(7165): 1063–1066. PMCID: PMC1114067 Copyright © 1998, British Medical Journal ABC of oxygen Oxygen at high altitude Andrew J Peacock

Atmospheric pressure and inspired oxygen pressure fall roughly linearly with altitude to be 50% of the sea level value at 5500m and only 30% of the sea level value at 8900m (the height of the summit of Everest). A fall in inspired oxygen pressure reduces the driving pressure for gas exchange in the lungs and in turn produces a cascade of effects right down to the level of the mitochondria, the final destination of the oxygen.

As explained in this article, the changes in breathing at altitude are due to atmospheric pressure changes, not by the volume of air in each breathe. How can a mask change atmospheric pressure? The mask cannot reduce the partial pressure of oxygen. With or without a mask each breathe will contain 21% oxygen with a constant partial pressure for the given altitude.

From trainingmask.com

ElevationTraining Mask is great because it regulates how much air you can breathe in, making it so that you breath less oxygen, in turn making the air thinner (due to the low oxygen intake it's similar to altitude training) . With reduced oxygen consumption the human body changes in several ways. The production of red blood cells and new capillaries (small blood vessels) increase the transfer of oxygen from the lungs to the rest of the body

If the mask can decrease the partial pressure of oxygen then their claims can be possible.

Trainingmask.com makes many claims that I find disturbing.

My personal take on the mask is that it doesn't change the partial pressure of O2, it provides resistance to airflow. I think to train breathing patterns, the mask may have some use but at a light to moderate exercise level. Which really can be accomplished by breathing through a straw, or swimming.

  • It could change the partial pressure of oxygen if the gas mixture coming through the mask has reduced oxygen (the total pressure is the same, but the partial pressure of oxygen is lower). Of course, the mask can't do this 24-7 so can't be as good as altitude training.
    – matt_black
    Commented Feb 10, 2012 at 14:11
  • How would the gas coming through the mask have reduced oxygen? Are you saying the mask would not only reduce the partial pressure of oxygen, but it would also increase the partial pressure of nitrogen? How will changing the volume of a gas, change the oxygen content? Is there less percentage O2 in a ml than a L of air?
    – Herms
    Commented Feb 19, 2012 at 12:59
  • It is easy to supply a mixture at atmospheric pressure that contains any gas content you want as long as you have a supply of the gases (stored in cylinders or produced by some sort of filtration). For example, people with breathing difficulties are often given enhanced oxygen supply (that is a gas mixture containing more than 21% oxygen). The issue is whether the "mask" contains any gas separation device to change what the wearer breathes.
    – matt_black
    Commented Feb 19, 2012 at 21:10
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    Exactly Matt, you can change the percentage by mixing gases. This mask doesn't, it is merely a restrictive device. Also decreasing the FIO2 will still not decrease the partial pressure.
    – Herms
    Commented Feb 20, 2012 at 3:39

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