Holding your breath can be a useful exercise, but its benefits are more specific and modest than many online claims suggest. Repeated breath holds activate your body’s dive reflex, stimulate the vagus nerve, and create brief periods of low oxygen that trigger some interesting adaptations. However, the performance gains are inconsistent in research, and practicing breath holds incorrectly carries real risks.
What Happens in Your Body During a Breath Hold
When you stop breathing, your body launches a coordinated stress response. Carbon dioxide builds up in your blood, oxygen levels gradually drop, and your heart rate slows as part of what’s called the mammalian dive reflex. This reflex redirects blood toward your brain and vital organs, essentially rationing your remaining oxygen supply.
Breath holding also counts as a vagal maneuver, meaning it directly stimulates the vagus nerve, the long nerve that runs from your brainstem to your gut and controls your “rest and digest” system. Activating this nerve shifts your nervous system away from its stress response and toward a calmer state, slowing your heart rate and lowering the intensity of your fight-or-flight signals. This is part of why controlled breathing practices that include breath holds tend to leave people feeling more relaxed afterward.
One notable finding: performing a series of breath holds in a row increases your body’s production of erythropoietin (EPO), the hormone that tells your bone marrow to make more red blood cells. Researchers measured an average 24% increase in circulating EPO after serial apneas. More red blood cells means more oxygen-carrying capacity, which is why competitive freedivers train this way. That said, this bump in EPO doesn’t appear to translate into lasting changes in hemoglobin levels or red blood cell counts unless the training is sustained over long periods.
Effects on Lung Capacity
Trained breath-hold divers consistently show lung volumes well above average, with vital capacities ranging from 5.9 to 7.3 liters compared to roughly 4 to 5 liters in most healthy adults. One study found that apnea training increased both lung volume and maximal aerobic capacity in swimmers. The catch is that serious divers don’t just hold their breath. They also do chest stretching, aerobic conditioning, and specific techniques to pack extra air into their lungs. Researchers have noted it’s difficult to isolate how much of the lung capacity improvement comes from breath holding alone versus the complementary training that accompanies it.
Still, the act of regularly expanding your lungs to full capacity and sustaining that expansion under pressure likely contributes to improved respiratory muscle strength and chest wall flexibility over time.
Does It Improve Athletic Performance?
This is where the evidence gets mixed. One study found that highly trained rugby players who warmed up with dynamic breath holds (holding their breath while moving) showed 6 to 8% higher peak power output and peak oxygen uptake during a cycling test, compared to a normal warm-up. Another study reported higher peak oxygen consumption after three months of breath-hold training during low-intensity cycling, using a protocol of 30-second holds alternated with 30 seconds of normal breathing.
But other research tells a different story. A well-designed study that tracked both blood markers and performance found no change in hemoglobin mass, peak oxygen uptake, or 3-kilometer time trial performance in either the breath-hold training group or the control group. The broader pattern across the literature is that breath-hold training protocols fail to demonstrate consistent, lasting improvements in aerobic performance.
During short, intense exercise bouts, breath holding doesn’t appear to shift your metabolism in a meaningful way either. When researchers compared 20-second all-out efforts with and without breath holding, blood lactate levels were essentially the same between conditions, suggesting the exercise was too brief to push the body into a different metabolic state.
The takeaway: breath holds may offer a short-term performance boost as a warm-up tool, but as a standalone training method for endurance, the evidence is thin.
Stress Management and Nervous System Benefits
Where breath holding shows more consistent value is in its effects on the nervous system. Because it stimulates the vagus nerve and promotes parasympathetic activity, incorporating breath holds into a broader breathing practice can measurably improve heart rate variability, a marker of how well your body shifts between stress and recovery states. Higher heart rate variability is linked to better cardiovascular health, emotional regulation, and resilience to stress.
Breathing techniques that combine slow exhalations with brief breath holds have been shown to lower blood pressure, reduce heart rate, and shift the nervous system’s balance away from its “alarm” setting. This makes breath holding particularly useful as a component of a calming breath-work routine rather than as a standalone cardio substitute.
Risks Worth Taking Seriously
The most dangerous scenario involving breath holding is shallow water blackout, a loss of consciousness caused by oxygen levels in the brain dropping too low before you feel the urge to breathe. This typically happens when someone hyperventilates before holding their breath underwater. Hyperventilation lowers carbon dioxide so much that the normal signal telling you to breathe is delayed. Meanwhile, oxygen continues to drop, and it can fall below the threshold for consciousness before carbon dioxide rises enough to trigger a gasp. In water, this means drowning.
The American Red Cross, U.S.A. Swimming, and the YMCA have jointly warned against hyperventilation before underwater breath holding. The takeaway is simple: never hyperventilate to extend a breath hold, and never practice breath holds alone in water.
On land, the risks are lower but still present. Breath holding during resistance exercise, sometimes called the Valsalva maneuver, produces the highest blood pressure spikes compared to other breathing patterns during lifting. For healthy people doing heavy lifts, a brief, controlled Valsalva can stabilize the spine, but for anyone with high blood pressure or cardiovascular concerns, those pressure spikes can be problematic.
How Beginners Can Start Safely
If you want to try breath-hold training, the simplest approach is a “no contractions” table. This means holding your breath only until just before you feel the first involuntary contraction in your diaphragm, the point where your body starts physically demanding a breath. You perform 6 to 8 holds with about two minutes of relaxed breathing between each one.
Start by finding your baseline: hold your breath comfortably and note the time when you feel that first contraction. That time becomes your hold duration for the first week. If you can complete a full week of sessions without hitting a contraction, add 15 to 20 seconds the following week. This gradual progression builds your carbon dioxide tolerance without pushing into uncomfortable or risky territory.
Avoid the temptation to use “classic CO2 tables” right away, which shorten the rest periods between holds while keeping hold times the same. These are more stressful on the nervous system and better suited for people who already have a solid baseline. Practice seated or lying down on dry land, and keep the focus on staying relaxed rather than chasing longer times.