Changes

At high altitude there is the same percentage of oxygen in the air, but the air is under lower pressure, so each lungful contains less oxygen. This causes a drop in the level of oxygen in your blood (called [[SpO2|SpO₂]]). Nearly all altitude training systems work by reducing the amount of oxygen in the air you breathe (hypoxia), rather than reducing the pressure (hypobaric). There are various ways of achieving this reduction in oxygen, but the simplest is to rebreathe your exhaled air. This works because you absorb oxygen from the air you breathe. Each time you rebreathe the same air the oxygen level drops. However, there is a problem with simply rebreathing the same air as the carbon dioxide levels rise as the oxygen level drops. Because your [[Breathing|breathing ]] rate is driven by the CO2 level in your blood, this will cause you to increase your breathing, which in turn will prevent any drop in your blood oxygen level. The solution is to breathe in and out via a chemical that will remove the CO2, called a CO2 scrubber. This is the function of the [[DIY Hypoxicator]], which is at the heart of this DIY system.

This altitude training system uses [[Intermittent Hypoxic Exposure]] (IHE), which uses repeated short periods of low oxygen (hypoxia) rather than a single overnight period that you would get with an 'altitude tent'. With IHE the hypoxia exposure is at rest rather than while exercising. Intermittent Hypoxia while exercising is called [[Intermittent Hypoxic Training ]] (IHT), though the terminology is used inconsistently. This system could be used for IHT, but I've not tried that.