Hypoxic training: what it is, how it works and who it makes sense for

Hypoxic training means training with less oxygen available than at sea level, either at real altitude or with equipment that simulates those conditions. For years it was a tool used almost exclusively by mountaineers and endurance athletes, but today it can also be found in some gyms and training centres. It's worth understanding what it is, what you can expect and what precautions are needed.

What happens in the body with less oxygen

When the air contains less oxygen, the body has to work harder to deliver the same amount to the muscles. In the short term, breathing rate and heart rate increase. If the exposure is repeated over several weeks, the body can adapt in several ways:

• A gradual increase in the production of red blood cells, which carry oxygen in the blood.
• Better use of oxygen by the muscles.
• Greater tolerance of exertion at altitude.

These adaptations are not the same for everyone. Some people respond well and others show hardly any difference, even when following the same protocol.

The main types of hypoxic training

There are several ways to apply the method, each with different demands and goals:

• Live high, train high: training camps of two to four weeks at locations above 1,500 to 2,500 metres. This is the classic approach, used mainly by endurance athletes.
• Live high, train low: the athlete sleeps and rests at altitude but does the hardest sessions at lower elevations, where they can maintain intensity.
• Intermittent hypoxia: short sessions using masks or rooms with oxygen-reduced air, alternating periods of hypoxia with periods of normal air.
• Hypoxic room training: cycling, treadmill or circuit workouts in a room with controlled oxygen levels, simulating a given altitude.

It's worth noting that training masks sold as "altitude masks" only make it harder for air to get in. They do not reduce the percentage of oxygen in the air and therefore do not truly reproduce altitude conditions.

Expected benefits and realistic expectations

For endurance athletes, especially those who will be competing at altitude, prior adaptation can help maintain performance and reduce discomfort in the first few days. Some people also report better breathing efficiency and a lower perceived effort when they return to sea level.

However, it's important to keep expectations realistic:

• The effects depend on regular exposure over several weeks; a single session changes nothing.
• For people who train for health or appearance, the gains are generally small compared with a good training plan, adequate sleep and a balanced diet.
• The response is highly individual, so the method should be tried cautiously and evaluated over time.

Risks and who should avoid it

Training with less oxygen places an additional strain on the heart and lungs. The most common symptoms of poor adaptation include headaches, dizziness, nausea, unusual tiredness and difficulty sleeping. If they appear, training should be stopped.

People with any of the following should talk to their doctor first, or avoid this type of training:

• Uncontrolled high blood pressure or heart disease.
• Respiratory conditions, such as poorly controlled asthma or chronic lung disease.
• Anaemia or other blood disorders.
• Pregnancy.
• A history of severe altitude sickness.

How to get started safely

If you're in good health and want to give it a try, follow a few simple rules:

• Do it somewhere supervised by professionals experienced with the method, with monitoring of oxygen saturation and heart rate.
• Start at a low intensity: in the first sessions, train at a lower intensity than you would in normal conditions, for example 20 to 30 minutes of moderate effort.
• Progress slowly: increase the simulated altitude or the duration only when previous sessions have been well tolerated.
• Stay well hydrated and get enough sleep: recovery is more demanding under hypoxia.
• Don't replace your foundation training: the method complements a well-structured plan; it is never a shortcut.

In summary

Hypoxic training aims to stimulate adaptations to exercising with less oxygen, through altitude camps or equipment that simulates altitude. It can be useful for endurance athletes and for people who are going to compete or go mountaineering at altitude, but results vary considerably and require weeks of exposure. It should be done under supervision, progressively and with attention to warning signs. This article is for information only and does not replace advice from a healthcare professional, who should be consulted before starting this type of training, especially if you have any health problem.