Freediving can be good for the lungs, increasing both capacity and function. The benefits of freediving are linked to thorough training, practice and observance of key safety rules (e.g. allowing sufficient surface rest time between dives).
The lungs and other airspaces in the body will always be under major pressure when freediving and this can cause lung squeeze and other barotrauma injuries, especially when diving at depth, not keeping safety rules, or diving beyond your competence. If you or your diving buddy experience lung squeeze symptoms, you should seek emergency medical treatment as quickly as possible.
The lungs can come under tremendous pressure when freediving. The total pressure experienced underwater is significantly greater than pressure experienced from the atmosphere at sea level on land, increasing by the equivalent of one full atmosphere for every 10m of descent below the surface.
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If you’re a freediver, or just interested in what happens to the human body when it comes under the high pressures encountered during deep dives, you may want to know more about what happens to lungs when freediving. Our article tells you more about the impacts of freediving on the lungs and how to mitigate negative effects.
Is freediving good for your lungs?
With intelligent training, regular practice, and gradual increases in depth and timing of dives, free driving can be good for your lungs. It also promotes physical and mental health more broadly. At the same time, freediving also places unique stresses on the cardiopulmonary system.
Freedivers face significant risks to lung health including increased hydrostatic pressure, hypoxia (low blood oxygen levels) and hypercapnia (high blood carbon dioxide levels). Risks can be more pronounced for for untrained divers, people with pre-existing lung conditions, or those who smoke.
Freedivers can increase their lung function and capacity by practicing effective breathing techniques and breath-holding exercises. For example, learning to fully exhale during the pre-dive breath-up, helps reduce residual volume, enabling the lungs to take in more air for the final pre-dive inhale.
With training and experience, freedivers do show enhanced lung function and capacity. These benefits can be realized even in people who are already very fit. For example, a group of elite athletes who completed freediving breath training reportedly increased lung function by 10%.
If you want to learn more, we’ve written a full article on why freediving is good for your lungs (opens new tab).
Why do lungs hurt after freediving?
The deep underwater environment of freediving exerts massive pressure on the human body. Even at shallow depths of a few meters, the forces experienced are significant. At 10m below the surface, water pressure is double the normal atmospheric pressure at sea level. For every further 10m of descent below the surface, water pressure experienced increases by the equivalent of one entire sea level atmosphere on land.
Gas volumes in the body’s airspaces decrease in inverse proportion to rising water pressures, in line with Boyle’s Law. The volume of lungs, ears and sinus airspaces in the human body are therefore increasingly compressed as we descend deeper into the water. At 10 meters below the surface, human lung volume is reduced by 50% compared to normal volume and this continues to fall.
As we begin to ascend from a dive, the volume of our lungs and other airspaces expands again. If we’re unable to equalize the gas pressure in our airspaces with surrounding water pressure, this leads to different kinds of barotrauma (pressure injuries). Tissue damage caused by barotrauma is commonly called a “squeeze”. “Lung squeeze” can be a serious injury requiring immediate medical attention.
How do freedivers increase lung capacity?
Lung capacity is important for freedivers, enabling them to take in as much air as possible on their final breath before a diving descent. More air means more oxygen and the potential for longer and deeper dives.
Both recreational and competitive freedivers may practice specific techniques and exercises to increase their lung capacity, including:
Segmented Breathing
Freedivers can use segmented breathing to increase consciousness and control of the different muscle groups used in breathing. Breathing from the lower chest and diaphragm as well as from the upper chest, increases overall lung capacity and efficiency.
Static apnea training
Systematically training for breath-holding using pre-defined training tables can build your body’s tolerance for high carbon dioxide and low oxygen levels.
Apnea walking (and other dynamic apnea)
Dynamic apnea exercises, including apnea walking, train the body to develop a greater tolerance to high carbon dioxide levels in the blood, and to low oxygen levels in peripheral regions which make muscles work anaerobically .
Lung packing / glossopharyngeal insufflation (GI)
Experienced freedivers may use the technique of glossopharyngeal insufflati on (GI), or “lung packing” to maximize the air in their lungs before descent. This maneuver allows them to add further air to the lungs after their final full inhale, by activating the glossopharyngeal muscles.
Do freedivers have bigger lungs?
Research has found that the lung volume of freedivers may be greater than that found in matched non-freediver controls. Lung size is an important factor in freediving performance for several reasons:
- larger lungs increase air and oxygen storage capacity,
- larger lungs enable more more carbon dioxide to be transferred to the lungs during a breath-hold,
- bigger lungs with a small residual volume (RV) can help achieve deeper dives with less risk of “lung squeeze”, since lungs won’t be compressed to RV until a deeper depth,
- greater lung volume facilitates equalization of the middle ears and sinuses.
While innate physical predisposition may give some freedivers higher than average lung volume, lung packing and other breath training used by elite freedivers have also been shown to boost lung capacity. Interestingly, stretching and lung packing together may increase capacity twice as much as lung packing alone.
What does lung squeeze feel like?
Lung squeeze is an injury which occurs almost exclusively in freedivers, also known as “chest squeeze”, or its formal medical name, pulmonary barotrauma of descent (PBT). It occurs when the lungs are damaged by the impacts of high water pressure on the body’s air spaces during a freedive.
Symptoms of lung squeeze can include severe coughing, wheezing and shortness of breath, chest pain and tightness, coughing up blood, and feeling weakness and fatigue. The condition can lead to secondary drowning, flooding the lungs with blood rather than water.
PBT generally occurs when a freediver reaches the residual volume of their lungs (around 20-25%), which happens roughly between 30-45m. There are also reports of lung squeeze occurring following multiple shallow dives separated only by brief surface intervals.
Increased pressure on blood vessels in the lungs under these conditions can damage capillaries, leading to rupture and leakage of blood and fluid with divers experiencing symptoms of pulmonary edema and hypoxemia.
As this condition does not occur in every freediver, at every instance of deep diving, there must also be other physiological mechanisms at play in triggering PBT. The exact pathophysiology of this condition remains unclear and further research is needed.
How do you recover from a lung squeeze?
Quick action is needed when a diver is suffering from lung squeeze. Diving should be stopped immediately and the injured diver towed to a location where they can safely exit the water. If available the diver should be given 100% oxygen. If they are fully conscious and able to breath properly, they should be given fluids.
Lung squeeze usually requires emergency medical attention in hospital to evaluate symptoms and deploy an escalating level of treatment depending on the severity and progression of the PBT. Where possible consulting a specialized diving physician is recommended.
After release from hospital, the affected diver should rest and recuperate for days or weeks to allow all the small pressure injuries in their lungs to recover.
With lung squeeze prevention is definitely better than cure. Freedivers can reduce the risk of PBT through measures including developing chest and diaphragm flexibility, maintaining good posture, and diving carefully in line with safety guidelines on depth and surface recovery time etc..
Why do freedivers’ lungs not collapse?
The science of freediving is still not fully explained and the precise mechanisms by which freedivers achieve such feats without collapsing their lungs are still partly unclear. One key appears to lie in thorough training, regular practice and gradually increasing depth and length of dive to allow the body to acclimatize to the extremes found at depth underwater. Activation of the Mammalian Dive Reflex (MDR) also plays a role.
We know that freedivers’ lungs and the air they contain both reduce in volume as the diver descends underwater. During a deep dive the chest cavity is compressed and blood pools in the chest from surrounding tissue, with blood being diverted away from peripheral regions and towards vital organs such as brain, heart and lungs.
Central pooling of blood in the chest equalizes the pressure gradient when the RV of the lungs is reached. This decreases the effective RV. These mechanisms allow the lungs to be compressed down as far as 5% of lung capacity in highly trained elite competitive freedivers. Once the diver ascends, the air and the lungs both gradually expand again as water pressure reduces.
When the study of freediving first began in the first decades of the twentieth century, physiologists thought that it would not be possible for human beings to dive below 30-40 meters depth. They calculated that beyond this level, the high water pressure would dangerously crush the body’s vital organs, including the lungs.
Today, freedivers have utterly smashed all early estimates or predictions around physical apnea and physical depth limits. Elite freedivers regularly exceed 100m depth for competitive dives, without experiencing obvious mechanical damage to the lungs or other parts of the body. The world freediving depth record now stands at over 200m. (Scuba divers may achieve even deeper dives of 300m+, or even deeper with the assistance of atmospheric suiting.)