The truth about gas mask training

Gas mask training has been falsely marketed to athletes as a ‘hypoxic training aid’, even though the composition of air filtered through the mask and into the lungs is the same as outside air.

The truth about gas mask training

By Dr. Jason Gillis

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Gas masks (respirators) are designed to filter out hazardous airborne contaminants from the air and provide the user with a clean air supply. Gas mask training has been falsely marketed to athletes as a ‘hypoxic training aid’, even though the composition of air filtered through the mask and into the lungs is the same as outside air (i.e. 20.94% O2; 0.03% CO2; 78.94% nitrogen, and other traces). The mask does not lower the percentage of O2 in the air you breathe, so it is not a hypoxic training aid.

Most masks cover at least the nose and mouth, and feature an air filtering canister or a small hole that limits air flow. This has the effect of increasing breathing resistance, particularly when ventilation rates approach and exceed the upper limit of what the respirator was built to accommodate; most commercial respirators can handle air flows of around 85 litres/min. Compare this with the normal air flow of resting humans (6 to 7 l/min) and those heavily exercising (120 to 140 l/min). From this, you can see that a respirator will exert little physiological influence during rest or moderate intensity exercise, but your ventilation rate will likely exceed the maximal air flow capacity of the mask when you are exercising heavily, and this can influence your physiology and performance.

When you exercise with a mask, your respiratory muscles must overcome the resistance imposed by the air filter or small hole in order to maintain adequate O2 and CO2 levels in the lungs, blood and muscles. The human respiratory system easily achieves this by increasing force production in the working muscles and by recruiting other muscles. All of this extra work comes at a cost because the respiratory muscles increase their demand for oxygen and blood. Also, the diaphragm, which is the primary muscle involved in active inspiration, requires a high proportion of blood flow during intense exercise anyway, and it may be susceptible to fatigue, even without the added work associated with wearing a respirator; so when a respirator is worn, the workload placed on the diaphragm is further elevated.

This additional work of breathing will limit exercise performance.1,2 The exact reason is not entirely clear, but is probably due to a competition over oxygen rich blood between respiratory muscles (primarily the diaphragm) and exercising limbs. In this view, a greater percentage of blood flow is diverted to the respiratory muscles and away from the working muscles, which increases limb fatigue.3 So, exercise with a mask can limit exercise performance and diminish the cardiovascular training stimulus.

Wearing a respirator during exercise will also increase breathing discomfort.2 As this is a probable driver of exercise pace, it seems likely that wearing a respirator during self-paced exercise will result in a lower work rate, which will diminish the cardiovascular training stimulus.

It should be stated that wearing a respirator during exercise will probably provide a stimulus to strengthen your respiratory muscles, so it might be considered a form of respiratory muscle training (RMT). But the most established forms of RMT use very different methods to stimulate adaptations in the respiratory muscles, so you should ask yourself ‘am I wearing the mask to improve my cardiovascular endurance, or to train my respiratory muscles’?

In my opinion, it is an inefficient use of your time to wear the mask if your training session objective is to stimulate cardiovascular adaptation; lose the mask and focus on stimulating your cardiovascular system with appropriate training loads. If you are wearing the mask to train your respiratory muscles, check that you are following the basic principles of respiratory muscle training.

Respiratory muscle training has been shown to improve exercise performance, and although less fit individuals seem to benefit more from RMT than highly trained athletes, all healthy groups can benefit.4 Interestingly, RMT may be useful for athletes competing in high intensity intermittent sports like MMA. This is supported by a study that showed a reduction in recovery duration between sprints, which was in part attributed to a decreased perception of respiratory effort.5

There are two types of RMT to consider, both of which are completed under resting conditions, without exercise (in contrast to gas mask training, which requires you to wear a mask during exercise).

Respiratory muscle strength training (RMST) consists of high force, lower velocity contractions of inspiratory and expiratory muscles. A typical workout might last around 5 minutes and include 30 dynamic inspiratory and expiratory efforts at 50% of you maximal inspiratory/expiratory mouth pressure, once or twice per day, 4-7 days per week, for 6 weeks.4  A typical device used for RMST is the POWERbreathe (

Respiratory muscle endurance training (RMET) consists of low force, higher velocity contractions of inspiratory and expiratory muscles. A typical workout might last around 15 to 30 minutes, and can be undertaken 2 to 5 times per week.4 The most important thing to remember with RMET is to maintain a normal breathing rate. A typical device used for RMET is the spirotiger (

 You should be aware of a few things when shopping around for devices; flow resistive training devices, like a gas mask, narrow the airflow path to provide resistance; this is comparable to breathing through a straw. Pressure threshold loading devices require a pre-determined pressure to be obtained before the valve in the training device opens, after which there is no further resistance during that breath.  Finally there is (voluntary) isocapnic hyperpnoea (increasing the depth of breathing), which is pretty much an endurance program.

 Closing notes

It is still not clear whether RMST is more or less effective than RMET. Although RMT can be undertaken by athletes of any level (amateur, semi-pro and pro), it should probably be reserved for professional fighters; the rational being that amateur and semi-professional fighters should be dedicating more training time to fundamentals such as skill development, and building a base of muscular strength and cardiovascular endurance. Professional fighters could use RMT, but it must be incorporated in addition to the normal training regime, and not as a replacement for a cardiovascular endurance training session, a strength/power or speed session, or skill development/MMA-specific session.


  1. Heus et al., 2004, Appl Ergo, 35, 583-90.
  2. Qiu et al., 2012, J Huazhong Univ Sci Tech [Med Sci], 32(2), 434-37.
  3. Dempsey, 2006, Respir Physiol Neurobiol, 151, 242-50.
  4. Illi et al., 2012, Sports Med, 42(8), 707-24.
  5. Romer et al., Int J Sports Med, 2002, 23(5), 353-60
The MMA Training Bible presents an evidence-based review of gas mask training for fighters and coaches in mixed martial arts

The MMA Training Bible presents an evidence-based review of gas mask training for fighters and coaches in mixed martial arts

Categories: featured posts, gas mask training, mixed martial arts (MMA), pseudoscience, Research, sport science

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9 replies

  1. I cannot find all of the articles from internet, but I still believe that respirator training will improve cardiovascular endurance, if trained properly. Let me give you following points;

    – Lets say that you do high intensity workout(rowing for example) for 2 minutes with a power of 500 watts(and lets say 500 watts is your maximum for 2 minutes, after that, your performance drops, because of fatigue). And lets assume, that after 2 mins you are very exhausted, breathing around 90% of your maximal capability of minute ventilation(lets say 120 litres / min). Now you put a mask on your face and row for 2 minutes with 500 watts, the masks reduces your maximal minute ventilation for 80 litres per min. What happens is that when you have your mask on, the oxygen you breathe still represents around 20% of the total volume, but the TOTAL VOLUME REDUCES and therefore reduces your oxygen intake, which indeed, causes hypoxia (in your system, not in the air!), hypercapnia and probably rise in lactate levels. How does that not give cardiovascular training stimulus as all of these factors will increase heart rate, respiration and bloodflow? I know that you said, that wearing the mask will reduce your training performance, but this is during training with the mask on. Of course your performance is reduced, but the main idea about the mask, is during training you try cause a condition, where muscles are deprived from oxygen, and therefore lactate acid, CO2, etc. starts to build up to the system. This CO2/lactate build up will stimulate different buffer mechanisms,heart rate and respiration system, which start to perform better, when training long term with gasmask. The idea is that, when you take your mask off, for example, competition, these buffer systems, heart, respiratory system, etc are now “trained” to compensate with the oxygen deprivation, lactate acid rise, etc, what comes when you are trying to go through your maximum limits during extremely high intensity activity(like MMA-competition). When you are training with respirator, it does not matter, if you cant run as much as without the mask, the point is that with respirator, its easier to have CO2/lactate levels/heart rate elevated, than without the mask. You should do a test; do one day high intensity exercise (around 2 mins) without the mask and one day with a mask and with the same time, measure your Hb saturation, lactate and heart rate. I think you will see a difference. And that difference is why people use these masks :)

    – Its important to know also that, if you are doing cardiovascular exercise with same tempo w/o mask and with the mask, your respirator muscles will compete the oxygen in your blood; this will give cardiovascular stimulus; you have more muscles training at the same time and your body is therefore using more oxygen and energy!

    – One important thing with these is that these masks do not work, if the minute volume your masks allows is too high compared to the minute volume you need for doing your activity. When you go over that limit, this is when your cardiovascular/respiratory/buffersystems gets their stimulus.

    All in all, I think the article was good, but you missed the most important points in the gas mask training

    1) These masks will work if your training is intense enough.
    2) The hypoxia comes from decreased minute volume, not from decreased precentage of oxygen in the air. Its important to know that you have to exceed the threshold for the maximal minute volume of the respirator with your own “demand” of air. If your body needs 100 litres per min and you get 60-70 litres,there will be hypoxia and all the other consequenses I wrote about.
    3) The masks does not allow the cardiovascular system to “go over limits”, but it will help to reach the hypoxia/hypercapnia/increased heart rate more quickly. This gives opportunity to traing more efficiently and with higher intensity load to cardiovascular system. It reduces the time for training or vice versa. if you traing short periods at a time, it will increase the amount of work you have done.


    • Thanks for the comment, and for the constructive feedback. I am sure readers will very much benefit from your insights, as I have.

      I agree with your assessment. Readers should take your point that although the mask does not lower the concentration of oxygen in the ambient air, it may create an hypoxic environment in the lungs, which may in turn lower the partial pressure of oxygen in the blood, thereby presenting an hypoxic training stimulus (so long as your breathing rate exceeds the capacity of the mask).

      You quite rightly allude that wearing a mask will most probably reduce power output during exercise at a fixed intensity, compared to when the mask is not worn during the same exercise. It seems probable that this reduction in power output is due in part to an increased reliance on anaerobic metabolism, and the associated build-up and lack of clearance of metabolic byproducts. I would like to emphasize that a comparable metabolic environment can be achieved by working at a higher power output without the mask.


  2. Thanks for this article!! the mask is not interesting for me now….there exist some portable device that actually reduce the o2 percentage in each breathe?

    sorry for my english!


    • Hi Carlos, thanks for your comment. There are portable hypoxic solutions, it is important to note however that much of the available research suggests that you should not train in a hypoxic environment, but rather train in a normoxic environment, and perhaps live in a hypoxic environment.

      Hope this helps,
      Dr. Gillis


  3. Hello

    As an up and coming athlete for GB, my training consist of a lot of endurance runs i.e 4x400m with about 6-7mins recovery and then we go again etc. I was interested in getting the RMST but if it only works for 2 mins how will i improve on my breathing when these sessions come about? Does this mean after each run i have to use RMST to restore my breathing again?


    • Hi Annie, thanks for your comment.

      I am no expert in RMST/RMET, however I believe the theory goes that by engaging in this type of training, you will strengthen the diaphragm, which will in turn lower the % of blood that would otherwise be directed to it during intense exercise. This extra % of blood would then be ‘freed’ up to deliver more oxygen and remove other metabolites from the engaged muscles.

      Last I read, it was recommended that RMET/RMST be completed as a separate stand alone session. Think of it this way; you have an endurance session, you have a session in the weight room, maybe you have a flexibility session, and maybe you have a RMT session.

      If you’re in the GB system, I suggest putting this question to your team physiologist – not sure if you’re in the English, Scottish, Welsh or Irish system however. I actually worked some time ago with EIS Manchester, and they are exceedingly qualified to advise you.

      Happy to discuss,

      Prof Gillis


  4. Hi I have been using the method of Gas Mask Training now on and off for a few years,
    Is it a placebo effect maybe but that is all the body needs more so the brain to push through the pain threshold.
    Last year I used the idea of training heart and lungs only keeping my THR to 70% and no more lets just say this was mentally painful. Did I find the benefit of this type of training, Yes I sure did but mentally I had to literally crawl up hills and wave to the 50 + yr old ladies as they passed me out. I tried this and got the results that I needed at the time.

    I want to point out that obviously this type of training has to be done under close supervision and structure also the key points here that will ensure a positive reaction is diet pre and also post training session.

    Over the last few weeks I have been keeping a very close eye on my performance levels and threshold and I have prolonged my sessions to 45min wearing the mask out of a total 60min.

    I do believe that there has to be some type of benefit to it. I suppose its like everything Variety is the key but not to put too much emphasis on it.

    I do not have the facility to measure my lactic levels at the end of my training sessions but I have noticed that I feel stronger and fitter over the last few weeks that I did whilst doing hill sessions and pyramiding.

    Time is the key here so hopefully it will prove a positive experience for me.



  5. Chemical Weapons Defense Advanced Gas Mask

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