I've recently seen several people ask about "altitude training" masks. Recently, I was asked by a runner I coach. Because this seems to be a hot issue, I thought I'd cover what I've seen as of now.
What is an altitude training mask?
First, what is an altitude training mask? This is the one I've come across in discussions. Maybe you've seen them around. I've never yet seen someone running with one but I have seen a couple people wearing them while weight training at the local Y.
What's the goal?
Next, let's have a quick review of what endurance athletes are trying to accomplish when going to altitude. We are trying to live in air with relatively low oxygen levels in order to stimulate the production of red blood cells as well as their ability to carry oxygen. In recent years, it's been discovered that you can get the benefits of altitude while living at altitude without suffering the drawbacks (primarily not as much oxygen available) if you travel to low altitude for training. That's why we have the concept of "live high, train low" and why quite a few elite runners these days have altitude tents in their bedrooms. They can sleep at simulated high altitude but train at low altitude.
Altitude training? Not quite...
This specific mask's promotional material states:
Training Mask 2.0 does not "change on the o2 molecular level" however your body does make adaptations for this "Simulation" to be considered "Altitude Training" also known as the "BOHR EFFECT"
So it's not reduced oxygen. That's a good thing because, if you were reducing oxygen levels, wearing the mask while running would have the opposite effect of what you're looking for. You want to "live high, train low" and this would have you living low, training high if you wore it while running and not at other times.
Resistance training? Possibly...
But what does this mask actually do, then? It appears that the claim is that it simulates high altitude by restricting your air flow.
Elsewhere on the same site, I see the claim of resistance while breathing building diaphragm strength and surface area and elasticity of alveoli, improving anaerobic thresholds and lung capacity. They mention studies but don't offer references.
Well, that's not what training at altitude does. Instead, the mask is a type of resistance training. The restricted airflow would add resistance that your respiratory muscles have to overcome. While that's not altitude training, is there a benefit to this?
I have now come across some references that help answering this question. In re-reading Science of Running by Steve Magness, I came across the topic of "respiratory training".
As Magness notes (with references, unfortunately, to studies I can't find online) a study by Romer evaluates the effect of respiratory muscle training and finds that it improves 20km and 40km cycling time trials by 3.8% and 4.6% respectively.
However, Magness also notes that similar studies have had mixed results and it appears the benefits are less significant in less well trained runners.
As noted in the book:
As we have seen, the degree to which the respiratory muscles contribute to VO2max varies based on training level. ... For this reason, higher-level runners should consider respiratory training, while lower level runners probably will not see the same degree of benefit.
Note: The site mentions building surface area and elasticity of the alveoli, improving anaerobic thresholds and lung capacity. The anaerobic threshold claim would seem to have some credence based on what I noted from the Magness book. I still have found no evidence for the claims related to the alveoli and lung capacity.
At this point, given the science I've seen and what we currently know about the benefits and drawbacks of altitude, I see limited benefit in this product. In fact, it might be counterproductive for some if used while running.
For the record, I attempted to contact the company linked to above so I could discuss benefits and concerns with them directly but, over a year after my first attempt to contact them, I never received a response.