Wim Hof breathing: how it works, the evidence and the risks

What is Wim Hof breathing?

Wim Hof is a Dutch extreme athlete known for feats in the cold, such as climbing mountains in shorts. His method has three parts: the breathing, cold exposure, and commitment or mindset. The breathing is a cycle of deliberate over-breathing followed by a breath-hold: about 30 deep breaths, a long hold after breathing out, then one deep breath held for about 15 seconds. Three or four rounds make a session.

We describe it here because millions of people try it, and they deserve an honest account of what it does and doesn’t do, and of how to stay safe.

Why there is no breathe-along guide

Every other timed exercise on this site has a breathe-along guide. This one deliberately doesn’t. The breath-hold after over-breathing can make you faint with no warning, and a guide that times holds and encourages you to keep going is the last thing you want at that moment. If you try it, go at your own pace, sitting or lying down.

What happens in your body

Breathing fast and deep blows off carbon dioxide faster than your body makes it. The fall in carbon dioxide causes the tingling in your hands and face, the light-headedness and sometimes cramping of the hands. See carbon dioxide and over-breathing.

The breath-hold is where the risk lies. The urge to breathe is driven mainly by rising carbon dioxide, not by falling oxygen. After over-breathing, your carbon dioxide starts so low that you can hold your breath far longer than usual. Meanwhile your oxygen keeps falling, and it can drop low enough for you to pass out before the urge to breathe arrives. On land you would usually come round quickly. In water you would drown. A review of drownings in New York State found 16 cases linked to dangerous breath-holding, including over-breathing before going under. See breath-holding and water.

What the research shows

The best-known study gave 12 men trained in the method, and 12 untrained men, an injection of bacterial toxin that briefly causes flu-like symptoms. The trained men had higher adrenaline, more of an anti-inflammatory signal called IL-10, less of the inflammatory signals, and milder symptoms. A 2024 systematic review of eight trials concluded the method may reduce inflammation, but found mixed effects on exercise performance.

The studies are few and small, and many involve healthy young men. There is no good evidence that the breathing improves fitness, helps you lose weight, treats depression or cures disease. We grade it as weak.

Who should not do it

Don’t practise Wim Hof breathing if you are pregnant, or have epilepsy, heart disease, high blood pressure that is not controlled, a history of fainting, or panic attacks, which over-breathing can trigger. See who should take care.

If you choose to try it

• Only on dry land, sitting or lying down. Never in water, the bath, the shower, a car, or standing up.
• Start small. Try 15 or 20 breaths instead of 30, and don’t chase long holds.
• Breathe normally for a few minutes before you stand up or do anything else.
• Stop at once if you feel faint or confused, or your vision changes.

If what you want is calm, resonance breathing or cyclic sighing have better evidence and none of the risk.