Wim Hof breathing does not appear to increase your actual lung capacity in the way most people hope. The research so far shows no significant improvement in ventilation parameters like tidal volume or breathing frequency in healthy individuals. However, the picture is more nuanced than a flat “no,” because one small study in people with spinal cord injuries did find a measurable improvement in forced vital capacity after practicing the method.
What the Studies Actually Measured
A study published in the Journal of Clinical Medicine looked specifically at whether the Wim Hof Method improves breathing economy during exercise. The results were disappointing for anyone hoping the technique would strengthen their lungs. The breathing program did not significantly alter tidal volume (the amount of air moved in a normal breath) or reduce breathing frequency. In practical terms, practitioners didn’t save any energy on the work of breathing, and there was no measurable improvement in breathing muscle function.
The researchers noted that focused breath training can, in theory, improve the strength and endurance of respiratory muscles. But whatever the Wim Hof Method does, it didn’t produce that effect in their study. The ventilation numbers stayed flat, suggesting the breathing muscles weren’t getting meaningfully stronger.
One Exception Worth Noting
A pilot study of 10 people with spinal cord injuries found a statistically significant improvement in forced vital capacity (FVC) after practicing the Wim Hof Method. FVC measures the total amount of air you can forcefully blow out after a full breath. Participants went from a median FVC of 2.8 liters to 2.8 liters at the higher end, with the interquartile range shifting upward from 2.4–4.5 to 2.7–4.7 liters. The percentage of predicted FVC also improved, moving from 76% to 79%. The effect sizes were large across all five respiratory parameters measured.
This is genuinely interesting, but it comes with important context. People with spinal cord injuries often have weakened diaphragms and compromised breathing muscles, so they have more room for improvement than a healthy person. A technique that helps someone recover lost function isn’t necessarily the same as one that pushes normal function beyond its baseline. The study was also very small and lacked a control group, so these results are preliminary.
Why It Feels Like More Capacity
If you’ve tried Wim Hof breathing, you’ve probably noticed you can hold your breath far longer than normal after a few rounds. This isn’t because your lungs suddenly hold more air. It’s because the rapid, deep breathing phase dramatically lowers your carbon dioxide levels. Carbon dioxide is the main signal that tells your brain “you need to breathe now.” By flushing it out, you delay the urge to inhale, which lets you hold your breath for what feels like an impossibly long time.
During the breath-hold phase, carbon dioxide gradually builds back up, and oxygen levels drop. Your body’s oxygen sensors eventually kick in, but they’re a weaker trigger than carbon dioxide. This creates a window where you feel comfortable not breathing even though your oxygen is actually falling. It’s a shift in your brain’s chemical signaling, not a change in the physical size or capacity of your lungs.
Over a 29-day protocol, one study found that Wim Hof practitioners did develop a significantly lower resting respiratory rate compared to a meditation group, with small additional reductions for every extra day on the protocol. Breathing more slowly at rest could reflect better carbon dioxide tolerance or more efficient breathing patterns. But a slower breathing rate is different from a larger lung capacity.
Lung Capacity vs. Lung Efficiency
This distinction matters. Your lung capacity is largely determined by your physical anatomy: the size of your rib cage, the elasticity of your lung tissue, and structural factors that breathing exercises can’t reshape. What can change is how efficiently you use the capacity you already have. Cleveland Clinic notes that diaphragmatic breathing helps you use your lungs at full capacity by training the diaphragm to engage properly, reducing the work of breathing and increasing the oxygen content of your blood.
The Wim Hof Method involves forceful, deep breathing that engages the diaphragm and intercostal muscles (the muscles between your ribs). In theory, this could strengthen those muscles over time, similar to how any repeated physical effort builds strength. But the clinical evidence so far hasn’t confirmed this in healthy people. The study that specifically looked for improvements in breathing muscle work found none.
What the Method Does Change
Where the Wim Hof Method shows more consistent effects is in areas unrelated to lung size. The 29-day trial found that practitioners reported greater energy, mental clarity, and stress-handling ability. Respiratory rate dropped. Heart rate dropped in the remote-practice group. These benefits accumulated gradually, growing with each additional day of practice.
The breathing technique also produces real, measurable shifts in blood chemistry. The hyperventilation phase raises blood pH by driving out carbon dioxide, creating a temporary alkaline state. Some researchers have speculated this could help buffer the acid buildup during intense exercise, potentially improving anaerobic performance. A pilot study on repeated sprint ability explored this angle, though results were mixed.
The cold exposure component of the Wim Hof Method, which is separate from the breathing, has its own body of evidence around inflammation and autonomic nervous system responses. But none of that relates to lung capacity either.
How Long Before You’d See Changes
Most Wim Hof studies use intervention periods of about four weeks. The 29-day protocol showed progressive improvements in respiratory rate and psychological measures that built day by day. The spinal cord injury study also ran over several weeks. Researchers have noted that substantially longer intervention periods may be necessary to see measurable improvements in physiological resilience traits, suggesting that a month of practice may not be enough to produce structural adaptations even if they’re possible.
If your goal is specifically to increase your measurable lung capacity for athletic performance or respiratory health, the current evidence suggests the Wim Hof Method isn’t the most direct path. Dedicated inspiratory muscle training devices, which create resistance as you breathe in, have a stronger evidence base for building respiratory muscle strength. Diaphragmatic breathing exercises, practiced consistently, can help you access more of the lung capacity you already have. The Wim Hof Method may offer many things, but a bigger set of lungs doesn’t appear to be one of them.