Do Altitude Tents Really Work?? Setting the Stage to Answer a Tough Question….

25 Jul

The Theory of Altitude Tents:

The theory of the altitude tent is relatively simple.  Sleeping in a hypoxic ( which means less oxygen than the “normal” 21% oxygen content of “air”) tent attempts to simulate some of the beneficial physiological responses that are well-established for athletes living in real-world high altitude environments.  Although there are several mitochondrial and metabolic changes that contribute to the benefits of high altitude living, the primary adaptation that people are after is:

Increased Erythropoiesis (what the heck is that?…it really just means making more red blood cells)

             When there are lower oxygen levels circulating in your blood (as is the case at altitude because the air is “thinner” and there is relatively less of every atmospheric gas, including oxygen, as compared to sea level) your kidney actually detects this low oxygen level and releases a hormone called erythropoietin, or EPO.  EPO then circulates in your body and tells your bone marrow to start producing more red blood cells.  More red blood cells result in increased oxygen carrying capacity of blood, hence increasing the oxygen in your blood to maintain the balance that keeps the kidney happy.  This increase of oxygen in the blood also boosts performance in endurance-related sports because more oxygen to muscle means the muscle can do more work, experience less fatigue and have less lactic acid produced for a given amount of exercise.  More oxygen carrying also implies a higher VO2max for those who like buzz words.  This EPO hormone is the same hormone that has made many professional cyclists infamous- the only difference is the injectable one is made in a lab, but it is the same hormone.  Interestingly, the primary legitimate medical indication for EPO use is kidney failure for the reasons described above.  The question remains whether or not a simulated hypoxic tent environment actually replicates this same biological response seen at altitude?

Diagram of Erythropoiesis (making more red blood cells)


Hypoxic Vs. Hypobaric:

A very important distinction to make when assessing altitude tents is the difference between hypoxic and hypobaric.  In the real world, high altitude is a hypobaric state.  Hypobaric means that all atmospheric gases are “thinner” at higher altitudes and therefore less abundant.  While less oxygen is available at high altitude, 21% of the “air” is still oxygen. The way an altitude tent works is different.  An altitude tent works under a hypoxic environment instead of a hypobaric environment.  The air has the same “thickness” as the altitude at which the tent is set up.  The hypoxic tent environment replaces part of the percentage of the “air” that is oxygen with nitrogen.  Hypoxic (and normobaric) means you are breathing less than 21% oxygen but the air is still “thick” like at sea level.  Unlike real altitude, there are lots of gas molecules around in a tent, just a little more nitrogen and a little less oxygen than the normal breakdown of air. The hypoxic vs. hypobaric distinction becomes very important when we look at the potential limitations of altitude tents and reasons why some physiological responses may be different. 

Of note, “normal” air is about 78% nitrogen anyways so nitrogen is very abundant and it won’t hurt you to breathe a little more of it for anyone who may think breathing nitrogen sounds scary. 

Responders Vs. Non-Responders

The term “responder” is a commonly used term in the altitude tent literature. It simply means that some people experience benefits from the tent in similar ways to altitude, while others do not. No one quite knows why it works for some people and not others. It is probably multifactorial and very complex.  There has been a particular interest in studying the association of a particular enzyme genotype, call the angiotensin converting enzyme, in association to whether or not someone is a “responder.”  This angiotensin converting enzyme is just a fancy name for an enzyme in our bodies that contributes to blood pressure control and it is postulated that it also plays a role in how we adapt to altitude, although the mechanism for this theory is not understood.  People inherit different versions of the gene that is in charge of this enzyme and it might make a difference what version of the gene you have. In short, some people may respond while others do not and we don’t really know why, but different gene makeups probably play a significant role.

So do the tents work….???

Ah ha!  So I have done a review of the current published scientific literature on this topic and I will be posting my impressions very very shortly….stay tuned….


Next topic up…Does compression wear really do anything?? Or are you just being duped into buying some really expensive old man tube socks??



4 Responses to “Do Altitude Tents Really Work?? Setting the Stage to Answer a Tough Question….”

  1. Dario July 25, 2011 at 9:50 pm #

    Hi Nicole – great article! I’m preparing for Pike’s Peak Ascent (starts at 6,300′ ends at 14,115′) so your article is pretty timely for me, too.

    I’m a flatlander (D.C.-area based) so the plan is get to CO a day or so b/f the race to try and minimize the high attitude affects as much as possible. No way to get there the recommended minimum of 10 or more days in advanced to acclimate.

    I was talking w/a guy who is former military the other day and he suggested doing some training w/an elevation mask ( or a surplus military gas mask.

    Apparently, the military uses this type to training to intensify workouts as well as to acclimate soldiers to higher altitude deployment.

    Wasn’t able to find any real research online search but I did find a story about Dick Beardsley who while injured and not able to run one winter strapped on an altitude mask and did fartleks shoveling snow.

    I’m all ears to any thoughts you have re: training w/a gas mask or elevation mask.


    • nkelleher July 25, 2011 at 11:51 pm #

      Hey Dario,
      Thanks so much for the question. Very cool that you are off to Pike’s Peak Ascent! I think your plan to get there just a day before if you cant do 10 days to 2 weeks is right on in order to minimize headache, sleeping trouble, dehydration, ect. Most pro triathletes have the exact same plan if they cant go out for at least 10 days-2 weeks beforehand.

      As far as the mask goes-
      This mask works in a similar fashion to snorkel devices that swimmers use in training to increase lung capacity and acclimate to not being able to breathe under the water (as well as focus on their stroke but this is irrelevant to this discussion). The snorkel significantly reduces the amount of air that enters the lungs with each breath, which is exactly what this mask is doing and is the mechanism by which the mask claims to work. I did a quick medical database search for any research on this type of mask device or the swimming snorkel and didn’t find anything relevant to your question. So unfortunately all I can give you is my impressions from a physiological standpoint without much research to back it up.

      I think the mask could be most beneficial in preparing your mind for the feeling of hypoxia during exercise (which I think is the big advantage in snorkel swim training.) I also think the mask may increase lung capacity to a degree. However, I don’t think the mask will actually have any change on your blood counts or metabolic adaptations. Unfortunately, the more significant changes of increased red blood cell counts, better buffering capacity of blood pH and mitochondrial changes that might occur at altitude require time (approximately 12-16 hours a day for 3-5 weeks) and so I don’t think the mask will make a big change there. However, I think being mentally prepared for the feeling of hypoxia is probably a huge benefit because your mind will control a lot of what your body is willing to do during your ascent. In short, I don’t think you will see dramatic effects at all, but you may feel more comfortable with the feeling of hypoxia after the mask and it might increase lung capacity- which can’t hurt. The price is pretty cheap too- just as long as you know you are paying for relatively minor benefits. Just be careful you don’t suffocate yourself in there!! Best of luck with the ascent!!

  2. Peter January 20, 2012 at 7:34 pm #

    Hey! Any impressions yet? 🙂

    Good luck,


    • nkelleher March 28, 2012 at 4:02 pm #


      So sorry!! I have been the absolute worst with keeping up with this site- going to try harder!!! After doing a lot of research on the topic I have realized that there is no way to currently know how well the tents work (super lame answer- i know). None of the research behind this topic is statistically powered to actually prove anything. If you are not a researcher- this basically means that all research is going to find some effect- whether that effect is due to chance or is real is reasonable ascertained through a statical term “power” which means you have to have enough study subjects to prove that your results are showing a real effect and are not just chance. The research with these tents, becuase they are so expensive and that arent a lot of athletes willing to be compliant enough to finish the study, there are very small numbers of subjects studied- which basically explains and makes somewhat scientifically irrelevant all the conflicting research on this issue.

      There are a few things that I belive are true at this point:
      1) You need to be in the tent a MINIMUM of 10-12 hours a day to see a physiological effect. Maybe more. But 10-12 is the absolute minimum.
      2) Results are extrememly individualized. I think this is well documented with altitude training in generally. Everyone responds differently. There is a risk of being a “nonresponder” and having it hurt your training, performance, recovery. There is a chance that it could help a lot too. But I dont think anyone knows until they try. It is my understanding that 2 of the 3 women (shalane f. and kara g.) who qualified for the olympics in the marathon trials this year have spent a lot of time in an altitude house living at sea level- could be rumor but that is the rumor. Basically- you have to see for yourself.
      3) lastly- if you are going to try it- you have to start low and take a long time to build. Also, I would start in the off season. I think these two things will give you the best chance of avoiding risk that you can control.

      I know this is probably not super helpful- but it is the truth of what I understand so far…wish I had something of more bite for you but it is what it is…

      Best of luck!!!

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