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You might have seen people in the gym training with an altitude training mask. These strange masks, like the one pictured below, sit around the mouth and the nose. Many people think that these can improve your performance by changing your breathing, recreating the effect of training at altitude while in the gym.

An example of an altitude training mask

The Elevation Training Mask 2.0. Source: https://www.trainingmask.com/

While I’m not aware of any professional sporting organisations that endorse them, plenty of individual athletes do.

But how well do they work? In this article we review the evidence supporting claims made about these masks. Do they stand up to scrutiny? Read on to find out.

How do altitude training masks work?

If you go to the website of one of the major producers of these masks they currently don’t make claims about altitude. Instead, they state that their masks are designed to ‘apply variable levels of load to respiratory muscles by controlling air flow pass through; this increases tension on your breathing – which makes you more powerful and efficient over a long workout.’

There have been several versions of the mask from this company, but as most of the research has examined their model 2.0, that’s the one we’ll discuss today.

From what I can work out though, the different brands and all models are all used roughly the same way. The mask fits snuggly over the nose and mouth. Some holes in the mask can be opened, or covered, with plastic caps. In the Training Mask 2.0, the combination used represents different altitudes. Fewer holes open makes it harder to breath (i.e. higher altitude), while more makes it easier.

Your expired air is captured in the mask, and will diffuse with air from outside the mask more slowly. So you are rebreathing air with a lower proportion of oxygen, and more carbon dioxide.

Do these masks simulate high altitude?

Altitude training has been used for a long time to lead to better performance in endurance events. However, experts disagree about if there’s much benefit, but here’s how it is thought to work:

At altitude, we get less oxygen with each breath, which restricts our ability to exercise. Red blood cell production increases, so that the oxygen carrying capacity of our blood improves. When you then exercise at sea level, this extra carrying capacity leads to a performance improvement.

The masks work differently.

They restrict the flow of fresh air, so you end up working harder to draw the same breath, like trying to breathe through a straw. You may also rebreathe some of your expired air, as mentioned above.

This is not the same as altitude, when the air is thinner, and both oxygen and carbon dioxide levels are reduced.

So we can’t assume the mask has the same effect as altitude. We need to test this. Luckily, there’s plenty of research we can look at to find out…

How well do altitude training masks work?

Now things get interesting! Unlike other fitness products, this one does use some research to support their claims. The website we looked at earlier cites one piece of research supporting how these masks work to improve fitness. The research was led by Professor John Porcari, who regularly assesses the claims of fitness products.

Porcari identified claims that the masks improved lung function, and VO2max, which is the maximum amount of oxygen we can take in when exercising. VO2max is a major limiting factor in our ability to exercise aerobically.

To test this, a group wearing a mask, and a group without the mask, did high-intensity bike training for six weeks (two sessions a week).

Both groups improved in VO2max. But there was no difference between them, so the mask didn’t make any difference here.

Ventilatory threshold improved in the mask group. This is the point while increasing our exercise intensity that we start relying on higher intensity energy systems. But most other measures didn’t change, and participants in the mask condition thought the exercise was harder.

So results were mixed. The conclusions were that the mask may have an effect, but doesn’t simulate altitude effectively.

So what is the effect of the mask?

Porcari and colleagues suggested that the mask may have an effect of training respiratory muscles, an idea which has some merit. But this didn’t lead to a performance benefit.

And this is the only piece of research they cite on this topic, which doesn’t fill me with confidence. This is an example of cherry picking, which means they are ignoring other evidence on the topic. So what does this other research say?

Cardio training effects of altitude masks

Other research has shown similar results*, though were less generous in their conclusions. Though there are a lot of variables researchers could look at, there are several key measures that show up regularly when testing these masks.

One is the saturation of oxygen in the blood. This is how much oxygen is transported, as a percentage of our blood’s capacity. This is usually 96-99% in the normal person at sea level. It decreases to about 80% at 4000m of altitude, though improves when you adapt to that altitude. If these masks simulate altitude, this should drop as the mask is worn.

Another is blood lactate, which is an indication of the contribution of anaerobic energy systems to exercise. At higher intensities, blood lactate builds up. At the same intensity, and in the presence of less oxygen, we could expect blood lactate levels to be higher.

Most importantly, aerobic fitness should increase over time. If the masks are effective, we should see an improvement in VO2max greater than when the same training is done without the mask. All the blood tests in the world aren’t as convincing as an actual performance benefit! Porcari’s research didn’t show this, instead pointing to change in some other scores which suggested it was plausible that it could happen.

A 2016 study found that oxygen saturation in blood was less when wearing a mask compared to a placebo mask (about 94% to 90%). But this only looked at individual bouts of exercise, not training over time. So they didn’t assess changed in fitness.

Other research compared the mask to hypoxic training in an altitude chamber, and a control group, for 6 weeks of interval training. They found oxygen saturation in the mask was no better than the control group, while the altitude chamber was. They concluded that the mask did not simulate altitude.

In fact, none of the research I could find has shown an increase in VO2max while using the mask that is greater than training without the mask (see also Biggs et al., 2017Sellers, et al. 2015Warren et al., 2017).

What about resistance training?

The training mask website presents one study showing that muscle hypertrophy was improved when using the masks, though strength wasn’t. This was quite a small study though, and the bulk of other research has shown there is no hypertrophy effect from training in hypoxia – and if you remember from earlier, it’s not clear that the masks even create this condition.

a man lifting weights wearing an altitude training mask

Unlike with cardio training, altitude training masks may actually make our exercise performance worse. “Training Mask Oceania” by Carly Reeves CC BY-NC-ND 4.0.

There are two other studies I’ve found that looked at resistance training using these masks, and their conclusions were the same: the masks don’t help our training performance.

One used both a mask and a control condition, and participants did 5 sets of squats and bench press until fatigue, with 60s rest between sets – a pretty hard work out! In the mask group participants failed earlier, recorded higher blood lactates, and perceived the exercise as harder.

So while the masks probably changed the energy system contributions during training (relying more on anaerobic metabolism), performance dropped. So we might benefit less from our resistance training. And more recent research has supported this.

A more recent, similar study found no difference in workload or blood lactate, but slower peak velocity of the bar during sets. So again, this may effect the adaptation we get from our exercise. And oxygen saturation was 97%, so the masks were probably not simulating altitude effectively anyway.

And as an additional issue, 3 (out of 26) participants reported discomfort, feeling light-headed, or experiencing anxiety while wearing the masks.

When we’re lifting weights, often we aren’t concerned about the energy system that is providing the fuel for our exercise. We are looking for a stimulus for our muscles and our nervous system. So making our training harder, and increasing anaerobic metabolism, may just reduce the effect of our training.

But if it feels harder, we often assume it is better for us. “No pain, no gain”, right?

So what’s the verdict on altitude training masks?

a cartoon man sitting on a giant question mark

Altitude training mask – what’s the verdict

As usual, the reality is more complicated than the marketing claims. It’s not just a case of reducing oxygen availability to increase fitness. The masks are not simulating altitude well enough to do this.

The evidence so far just doesn’t provide clear support for the use of these masks to improve fitness. They may stress the breathing musculature, which in theory could improve lung capacity and deliver more oxygen to working muscles over time.

But exercise with the masks feels harder… therefore it must be working, right?! It’s a common idea today that when exercising, the harder the better! But this misses the point. We can train at the right intensity, for the right length of time, in the right way, to get the effect we want. More, or harder training, does not automatically mean more benefit.

The final word

two people questioning the evidence

Want to try altitude masks? Go for it. But the evidence to support them isn’t great so far. Image by freepik – www.freepik.com

To be generous, I’d say the verdict is mixed**. If you want to give it a try, go for it. If the mask has an effect, it’s a small one. We’re yet to see a clear benefit with cardio training, and the different mask settings don’t seem to make a difference.

And it seems that your resistance training suffers. You’re probably not able to provide the same stimulus to the muscle as you would without the mask. In the long run, that will hurt any size and strength benefit you are looking for.

*I excluded some research that only looked at single bouts of exercise, or when mask and control conditions were not matched for exercise intensity or duration. Both these issues limit what real world applications we can get from this research.

**if you want another opinion, try this summary. It’s about a year older than this one, and draws on slightly different research, but reaches a similar conclusion.