The science

What happens in a fast breathing session?

By GyroscopeUpdated November 15, 202614 sources

Fast rounds like Wim Hof breathing blow off carbon dioxide faster than your body makes it. That’s what causes the tingling lips and fingers, the cramping hands and the head rush. It also quiets the urge to breathe, so the hold that follows feels easy while your oxygen drops, and that’s why people pass out.

The sensations in a fast session are strong, and that makes them feel like proof. People say they’re flooding their body with oxygen, releasing stress or “changing their blood chemistry,” and the tingling and buzzing seem to confirm it. Most of what you feel comes from one change: carbon dioxide falling well below normal. It’s a real change in your body. It’s also mostly a side effect.

What happens in one round?

The Wim Hof Method’s own instructions are simple. Sit or lie down. Take 30 deep breaths in a row, filling your belly and letting each breath out without force. After the last one, breathe out and hold on empty until you feel the urge to breathe. Then take one big breath and hold it for 15 seconds. That’s one round, and the method suggests three or four. Here’s what happens in your body along the way.

1. The first breaths. You’re breathing far more than your body needs, so carbon dioxide leaves your blood faster than your cells make it. Your blood turns more alkaline.
2. The tingling. Lips, fingers and feet start to buzz. MedlinePlus lists numbness and tingling as symptoms of low carbon dioxide, and the method’s page says you may feel lightheadedness and tingling.
3. The head rush. Blood vessels in your brain narrow when carbon dioxide falls, so brain blood flow drops. You feel light, spacey or dizzy.
4. The hands. In long or intense sessions, hands and feet can cramp and curl, which people call lobster claw. MedlinePlus lists spasms in the hands and feet as a symptom too.
5. The hold. With carbon dioxide low, the alarm that makes you want to breathe takes much longer to go off. Low carbon dioxide is one of the things known to stretch a breath hold.
6. The oxygen drop. Your body keeps using oxygen through the hold. In a 2014 Dutch study, people practicing these techniques had repeated bouts of low blood oxygen along with the alkaline blood.
7. The adrenaline. In the same study, adrenaline in the blood rose sharply. That’s the buzz and the alertness afterward.
8. The recovery breath. The big breath and 15-second hold bring oxygen back up. Then the next round starts.

A simple way to picture it

Think of the urge to breathe as an alarm clock, and fast breathing as hitting snooze. The alarm goes quiet for a while, but the clock keeps running. During the hold, oxygen is the clock. If the snooze lasts longer than you have oxygen for, you never hear the alarm before you pass out.

Why do people pass out?

Normally you can’t hold your breath until you black out. A strong reflex forces the next breath first. Fast breathing beforehand changes that, because it lowers the carbon dioxide that reflex mostly responds to. The American Red Cross, the YMCA and USA Swimming call losing consciousness under water after hyperventilating “hypoxic blackout,” and it can happen in any body of water at any depth.

The Wim Hof Method’s page says its breathing, “when done intensely for multiple rounds, can in rare cases lead to loss of consciousness.” Its FAQ says that fainting while lying down carries little danger, but that it means you went a little too far. Its safety page is blunt about the rest: “Never attempt the exercises before or during diving, driving, swimming, or taking a bath.”

Fainting on a bed is mostly harmless. In water, fainting can lead to drowning, as the method’s own FAQ warns, and at the wheel it can cause a crash.

What did the famous Wim Hof study find?

In 2014, doctors at Radboud University in Nijmegen, in the Netherlands, split 24 healthy volunteers into two groups of 12. One group trained for 10 days in meditation, fast breathing with holds, and cold exposure, including dips in ice-cold water. The other group didn’t train. Then everyone got an injection of a bacterial toxin that brings on a short, flu-like reaction.

The trained group did better. Their adrenaline levels shot up, an anti-inflammatory protein rose faster and higher, inflammatory proteins stayed lower, and they had milder flu-like symptoms. Their cortisol, the stress hormone, was no different from the untrained group’s before or during the breathing, and it came back down faster afterward.

It’s a striking result, and people often quote it as proof that breathwork lowers inflammation and cortisol. It shows something narrower. Twelve volunteers, trained in three things at once, handled one lab challenge better, with a big rise in adrenaline during the practice. It doesn’t show that fast breathing at home lowers inflammation or stress hormones in daily life.

What about holotropic and 9D?

Holotropic breathwork was developed by Christina and Stanislav Grof in 1975. It’s deep overbreathing to music, sometimes with bodywork, and a typical session lasts one to three hours. Two researchers who wrote about it in 2007 called it “a prolonged, voluntary hyperventilation procedure” and said better studies would be needed to show whether it helps with anxiety or depression. A 2015 paper on it said the research is sparse. Holotropic breathwork has what a session is like and what a 2025 study measured.

9D breathwork is a branded format its makers call conscious connected breathing, played over “nine layers” of sound such as binaural beats, in recorded sessions of about 12 to 23 minutes. We couldn’t find a published study of it. If a session has you breathing faster or deeper than you need, the same chemistry and the same rules apply. What is 9D breathwork? has more.

What does the evidence say about fast rounds?

The same review mentions a trial of fast breathing in people with depression where a few people had hot flushes, shortness of breath or sweating, though none dropped out because of it. The review’s authors call for more research on the safety of fast-paced breathing.

Fast rounds do something. They wake people up, and in the Stanford trial they lifted mood about as much as the slow patterns did. They’re much weaker for anxiety, and they’re the only kind of breathwork with a real risk of fainting. We’d use them for a jolt of energy, on dry land, if at all.

The rules

• Sitting or lying down only, on a bed, a mat or the floor.
• Never in or near water. No pools, no ocean, no bath, no hot tub, and never right before swimming or diving.
• Never driving, or anywhere passing out could hurt you.
• Skip it entirely if you’re pregnant, or if you have epilepsy, coronary heart disease, a history of heart failure or stroke, or high blood pressure you take medicine for. That’s the method’s own FAQ. In children with absence epilepsy, breathing hard on purpose sets off a seizure in 87 to 100 percent of them.
• Keep holds comfortable. Breathe when you feel the urge. Don’t try to beat your last time.
• If you faint, you went too far. Take it easier next time, as the method’s own page says.
• In cold water, breathe normally. The method’s FAQ says so too.
• Chest pain, a racing or irregular heartbeat, or trouble breathing that doesn’t settle means stop and get help. Call emergency services for chest pain.

Who should skip which breathing exercises? covers the slow patterns and holds as well.

What changed from our old guide

Gyroscope’s old guide described the cramping “lobster claw” as “a perfectly normal and common reaction” that “can often be a good sign,” meaning you were breathing hard enough to change your blood chemistry. The first part is right. It’s common, and it passes. The second part isn’t. Cramping hands mean carbon dioxide has fallen a long way, which is the same change that makes the hold easy and fainting more likely. We’d treat it as a sign to slow down. Tingling hands mean it’s working has the rest.