The Wim Hof Method (WHM) is one of the most-talked-about breathing protocols of the last decade. Wim Hof is a Dutch extreme athlete known for cold-exposure feats. The method bearing his name combines three components: a breathing protocol, cold exposure, and a meditation/commitment piece.
The breathing protocol does real, measurable things — just not the things slow resonance breathing is studied for. The popular framing of WHM as “a way to raise HRV” is not supported by any controlled trial we could find, and is worth correcting carefully.
The protocol
A single round of the breathing portion of WHM:
- Sit or lie down. Take 30 to 40 fast, deep breaths through the mouth or nose. Inhale fully; exhale loosely (less complete than the inhale). This is deliberate hyperventilation; expect to feel lightheaded and tingly.
- After the last exhale, hold your breath for as long as comfortable.
- When you feel the urge to breathe, take one full inhale and hold for 15 seconds.
- Release and breathe normally for 30 seconds.
- Repeat for 3 to 4 rounds.
That’s the breathing portion. The full method usually pairs this with cold exposure — cold shower, ice bath, snow immersion.
What the breathing actually does
The hyperventilation phase blows off carbon dioxide; the breath-hold that follows lets it build back up while oxygen falls. The randomized trial that put the method under controlled conditions, at Radboud University in the Netherlands, measured what that does: intermittent respiratory alkalosis, hypoxia, and a large rise in plasma epinephrine — adrenaline.
“In the intervention group, practicing the learned techniques resulted in intermittent respiratory alkalosis and hypoxia resulting in profoundly increased plasma epinephrine levels.”
In other words, the breathing is a sympathetic stimulus — the adrenaline arm of the nervous system. Slow-breathing research measures the other arm: a 2022 meta-analysis of 223 studies found that voluntary slow breathing increases vagally-mediated HRV. Same lungs, different direction.
Why we don’t consider Wim Hof an HRV protocol
The HRV number people track is the baseline— the resting or overnight value a wearable reports — not the swings inside a single session.
Slow breathing has a literature on exactly that: the same meta-analysis found increases in vagally-mediated HRV after multi-session interventions, not only during the breathing itself. Wim Hof has nothing comparable. The 2024 systematic review of the method found nine papers; its positive findings were on the inflammatory response, and its findings on exercise performance were mixed. We have not found a controlled trial showing that WHM raises resting HRV.
What the evidence actually shows for Wim Hof
The strongest evidence supports one specific claim.
Voluntary modulation of the inflammatory response. Kox et al. (2014, PNAS) trained 12 healthy volunteers for 10 days in the method’s meditation, breathing and cold exposure, then gave them and 12 untrained controls an intravenous dose of bacterial endotoxin. The trained group had higher levels of the anti-inflammatory cytokine IL-10, lower levels of the pro-inflammatory TNF-α, IL-6 and IL-8, and fewer flu-like symptoms. The authors attribute it to the adrenaline release the techniques produce.
The same group reproduced it and took it apart. In Zwaag et al. (2022, Psychosomatic Medicine), 48 healthy young men were randomized to cold training, the breathing exercise, both, or neither. Cold training alone did not relevantly change the inflammatory response; the breathing exercise did, and adding cold made it stronger. This is real, replicated immunology — in small samples of healthy young volunteers, in a laboratory. The authors describe it as paving the way for clinical trials, not as a treatment.
Everything else is weaker:
- Exercise performance — the 2024 systematic review calls the findings mixed.
- Mood — the 2023 Stanford trial included a Wim Hof-style arm (cyclic hyperventilation with retention). Breathwork as a group beat mindfulness meditation on mood; the protocol the authors single out is cyclic sighing, not this one.
- Cold tolerance, cognition, resting HRV, and any disease treatment — we found no controlled trials that support claims here.
When not to do Wim Hof breathing
The protocol has a real safety profile. Several contraindications are firm:
- Never in water. Hyperventilating and then holding your breath can cause loss of consciousness without warning; underwater, drowning follows. A New York State review (Boyd et al., 2015, MMWR) was prompted by two healthy young men who died after intentionally hyperventilating before going underwater, and found 16 fatal and nonfatal drownings linked to dangerous underwater breath-holding behaviours. Do the protocol seated or lying down, on a soft surface, never in or near water — not a pool, not a bathtub.
- Never while driving. Same loss-of-consciousness risk.
- Not during pregnancy.The controlled trials above enrolled healthy volunteers — the 2022 one, men only. None of them tells you it’s safe here.
- Not if you have epilepsy or seizure history. Hyperventilation is used as a provocation method in routine clinical EEG precisely because it can bring out epileptiform activity.
- Not if you have panic disorder or active anxiety. The protocol produces panic-like sensations (tingling, lightheadedness, derealization) deliberately. For panic-prone people, that can set off an actual panic attack rather than the trained equanimity the method aims for.
- Not if you have a heart condition. The breathing produces a large adrenaline surge — it is the mechanism in the Kox trial. Talk to a cardiologist before starting if you have a history.
When Wim Hof might be the right pick
For a healthy adult who is curious about it, doesn’t fall into any of the contraindication categories above, and understands that the evidence is one line of immunology research — Wim Hof is a legitimate protocol with a real documented effect.
It is a complement to slow breathing practice, not a replacement. The two pull in different directions — adrenaline on one side, the slow-breathing HRV literature on the other — and they can coexist in the same person’s week. Expect different things from each.
One common assumption is that the cold does the heavy lifting. For the inflammatory effect, the evidence says the opposite: in the 2022 Radboud study, cold training alone did not relevantly change the response; the breathing did, and cold amplified it.
Why HRV Breathe doesn’t include it
Three reasons. First, the protocol doesn’t serve the HRV-focused use case the app is built around. Our positioning is “the breathing app for people who measure things,” and the documented effects of Wim Hof breathing are on adrenaline and inflammation, not on the resting HRV people track.
Second, the safety profile requires more guardrails than a visual breath pacer can reasonably provide. The protocol can produce loss of consciousness; we’d need contraindication screening, supervision recommendations, and water/driving warnings that fundamentally change the product experience.
Third, Wim Hof has his own well-developed teaching ecosystem. The official app, his book, the certified instructors, the retreats — there’s a complete infrastructure for people who want to learn the method. Duplicating it without doing it better isn’t useful.
If the method appeals, use the official Wim Hof Method app. Use HRV Breathe for daily slow breathing. The two practices don’t compete for the same slot.