Picture yourself lying on a lounger, breathing through a light mask and doing — nothing. No racing heart rate, no sweat, no effort. And yet, over those 20 to 40 minutes, your body receives a very clear signal. That is IHHT: intermittent hypoxic-hyperoxic training, or simply cell training.
The alternation is the whole trick
The mask first delivers oxygen-reduced air, roughly what you would breathe at 3,000 to 6,000 metres of altitude. A few minutes later comes a phase with oxygen-enriched air. Then thin air again. This alternation — hypoxia, hyperoxia, hypoxia — repeats several times per session. It is the rhythm that creates the stimulus, not the altitude alone.
Throughout the session, oxygen saturation (SpO₂) and pulse are measured continuously. Those readings drive the intervals: if saturation drops faster than planned, the device switches earlier. Everyone gets their own dose instead of working through a fixed programme.
- Length: usually 20 to 40 minutes, seated or lying down.
- Not a workout: no exertion, no movement, no warm-up.
- Individually controlled: SpO₂ and pulse shape the session.
- Repetition matters: sessions come in series over several weeks.
Why cells respond at all
Every cell has an oxygen sensor. When supply falls, it switches on a set of genes that reorganise how oxygen is handled. The proteins in charge are the hypoxia-inducible factors, or HIFs. Decoding that mechanism earned the 2019 Nobel Prize in Medicine [1]. The work of Semenza and colleagues shows how finely this switch operates and how many processes depend on it — from red blood cell production to a cell's energy budget [2].
IHHT uses a principle every cell already knows: scarce oxygen as a signal, not as damage.
What that means for a single session
The stimulus is deliberately mild and short. The point is not to push your body to a limit but to give it a reason to fine-tune how it uses oxygen. That is why a session feels more like a break than a workout — and why series work better than one-off appointments.
How solid the research is depends entirely on the question you ask. Controlled studies exist, including a pilot study on cognitive performance in mild cognitive impairment [3], but groups are usually small and protocols differ. Anyone turning such work into a promise of healing is going far beyond the data.
- Well established: how cells sense oxygen in the first place.
- Under study: the effects of specific protocols on performance, sleep and cognition.
- Still open: the optimal dose and who benefits most.
If you want to try it
Start with an honest conversation: what you want to achieve, what argues against it in your case, how many sessions are realistic. Then you can decide whether IHHT fits you at home, in a practice — or not at all.