Normobaric Hypoxia vs Hypobaric Hypoxia: what are the differences and which is best?

Thanks to years of research, there is an abundance of evidence highlighting the extensive benefits of altitude training, from improving athletic performance to general health and fitness gains.

So, what actually is altitude training and how is it best utilised?

The key to altitude training is a reduced oxygen availability, otherwise known as hypoxia. However, did you know that simulated altitude is slightly different to real, terrestrial altitude? So, what gets the best results?

In the atmosphere, as you increase the altitude, the overall percentage of oxygen stays the same, but the air pressure decreases. Essentially this means there is less air, meaning with each breath, you take in less air and therefore less oxygen. This type of hypoxia is known as hypobaric hypoxia, or ‘real altitude’. However, due to the logistical difficulties of reducing air pressure, most simulated altitudes, like our chamber here in London, are created by keeping the air pressure the same but reducing the oxygen concentration. This is known as normobaric hypoxia, or ‘simulated altitude’.

Both hypoxic conditions can create the exact same partial pressure of oxygen, aka the amount of oxygen we can take in. Consequently, it is often assumed that both produce the same responses and can be used interchangeably. Upon first glances at research, this seems to be the case, with similar performance improvements being shown with both real and simulated altitude training.

Recent research however is looking more closely into the physiological responses between both hypoxic conditions has found that there may be some interesting differences between the two.

So, what do the results tell us?

Training in hypoxia

It appears that training at ‘real altitude’ results in lower blood oxygen saturation than ‘simulated altitude’ conditions of the same partial pressures. This may be due to the reduced ventilation (i.e. breathing rate) and tidal volumes (i.e. amount of blood being pumped out the heart per beat) reported at real altitude. If you are breathing less, you will be taking in less oxygen into the blood. This combined with a reduced amount of blood being pumped per beat, means there will be a reduced blood flow and therefore oxygen to muscles, limiting exercise duration and intensity. Some may argue that this leads to greater adaptation and thus performance in the long term. However, as previously mentioned, the majority of research shows that there are no performance differences post training between the two types of hypoxia.

So what does that mean?

During ‘real altitude’ training, we put the body through more oxidative stress, but get the same results as we do training in ‘simulated altitude’. The fact that our body can tolerate simulated altitude conditions better, while producing the same results as training at ‘real altitude’ would suggest that ‘simulated altitude’ is the best option for training.

When you factor in the logistical difficulties of travelling to real altitude, time away from work, families and adapting to a new environment – it’s no surprise we are seeing far more simulated altitude camps among elite and non elite sports, and still seeing advances in performance!


Sleeping in Hypoxia

As well as training benefits, simulated altitude has also been shown to be more beneficial when sleeping. Sleeping at ‘real altitude’ has demonstrated more maladaptive, periodic breathing leading to nocturnal IHE compared to ‘simulated altitude’. This can be disruptive to sleep, waking people up in the night, and can even continue after waking, leading to training and performance detriments. This is important to consider for people who are taking the live high, train low approach and for mountaineers who are aiming to get maximal hypoxic exposure.

If you have the money, and the time, a month in the Alps could well be a great option for you (and an incredible holiday to boot). For those that don’t, simulated altitude offers an incredibly accessible alternative, with equally as beneficial adaptations.

What does this research mean?

The take away from this is that the benefits of altitude does not require trekking to great heights for intensive training camps. You can gain the same benefits, and more through being able to push yourself to a higher intensity, in the safer environment of our simulated altitude chamber right here in London! Or to make it even easier, we can bring the altitude to you! Whether it is for exercise using our generators and masks, or whether it is for sleep with our hypoxic tents, we can bring you to the mountains whilst at the comfort and safety of your own home. For more information on the benefits altitude training and what we can offer, get in touch below!

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Review reference:

Coppel, J., Hennis, P., Gilbert-Kawai, E., & Grocott, M. P. (2015). The physiological effects of hypobaric hypoxia versus normobaric hypoxia: a systematic review of crossover trials. Extreme physiology & medicine, 4(1), 1-20.