Despite the major demands it makes on the body, freediving can be a very safe and healthy sport when practiced in line with safety guidance and mastery of physical techniques including apnea and ear pressure equalization.
At the same time, some medical conditions might raise the risks of freediving to dangerous levels. People with lung, heart and other relevant conditions must take medical advice before freediving and no one should freedive with a cold or similar respiratory infection, or after drinking alcohol.
Freediving is a highly demanding sport which puts great pressures on the bodies and minds of freedivers. This means that solid training, practice, and adherence to safety rules are all essential for freediving safely and a high level of performance. With the right preparation and guidelines in place, freediving can have a significant beneficial effect on the human body.
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Whether you’re already a freediver, or thinking of trying freediving, you may have questions about what happens to your body when you freedive. In this article, we tell you more about the benefits and risks of freediving, as well as the measures you can take to stay safe and get the most from this unique sport.
The benefits of freediving for your body
There are a number of physical benefits which can be derived from freediving as well as its positive effects on mental health and function. It has the potential to boost almost every dimension of physical fitness.
While freediving you are engaged in both aerobic and anaerobic activity, while experiencing massive water pressures on your body from all sides, and controlling your breathing under the influence of the ‘Mammalian dive reflex’ (MDR), which allows mammals including humans to hold their breath longer underwater than on land.
Lung capacity and function
When apnea (breath-holding) is practiced correctly after robust training, freediving can increase lung function and capacity. In a group of elite athletes who practiced freediving breath training exercises, participants were reportedly able to boost their lung function by around 10%.
For more details on why freediving can be good for your lungs, check out our article; is freediving good for your lungs (opens new tab).
Physical strength
Water is far denser than air which means that our muscles have to work proportionally harder to perform the same movements underwater as on land. As we get deeper, the water pressure increases and the effort required to move goes up alongside it. Working harder helps to make muscles stronger, and diving or swimming underwater can therefore boost our physical strength.
Healthy weight
Combining both aerobic and anaerobic metabolism means that freediving can burn a very high number of calories (anywhere from 400-1200 calories per hour, depending on body size, water condition and temperature, periods of swimming, dive depth and length etc..).
Maintaining a core body temperature may be the principle driver of this high calorie consumption, since freediving general involves immersion in deep areas of open water well below normal body temperature. This forces the body to constantly draw on its energy stores to stay warm and overweight beginner divers may therefore lose any excess weight quickly if they are regularly in the water.
Mental health
Freediving can lead to a calmer mind, greater focus and lower stress levels. High levels of stress chemicals in the body (cortisol, adrenaline etc…) have a negative effect on various organs and functions, and lowering stress can have a positive overall physical effect.
The cons of freediving for your body
During a freedive, divers face risks to different organs and parts of the body posed from rising hydrostatic pressures, as well as low blood oxygen (hypoxia) and high blood carbon dioxide (hypercapnia).
Pressure on the body underwater is significantly greater than normal atmospheric pressure on land at sea level. For example, pressure is doubled at 10 meters depth in the water, with pressure continuing to increase by one full atmosphere equivalent for every additional 10m of descent.
The airspaces in the body (ears, lungs, sinuses) can be massively compressed as pressure increases, reduced to under half normal volume during the deepest dives.
Ear damage
Well-trained and experienced divers without medical issues will not normally experience ear pain or discomfort. Freediving without understanding compression of the body’s airspaces and learning how to equalize pressure in the ears could be both painful and damaging. Beginner freedivers must learn how to equalize the pressure in their ear airspace as they descend. If you cannot equalize ear pressure for any reason, you should abort your freediving plans.
There are several ear-related medical conditions which can affect freedivers including:
Otitis externa (swimmer’s ear): an ear infection caused by bacterial growth from stagnant water left inside the ear.
Barotitis media (middle-ear barotrauma): a common diving injury, occurring when water pressure during descent causes leakage of blood and other body fluid into the middle ear.
Inner-ear barotrauma: equalizing pressure in the ears with too much force, can over-pressurize the middle ear, damaging the inner ear.
Ruptured eardrum: perforation or rupture of the eardrum through water pressure can happen to some individuals at depths as shallow as 2 meters.
Lung damage
Freediving places unusual stresses on the whole cardiopulmonary system, creating risks to lung health, particularly for poorly trained divers, smokers or those with pre-existing lung conditions. Like the ears, the airspaces in the lungs may be compressed drastically during a freedive and its important that freedivers understand what is happening and how to control their breath and dive speed to best protect their bodies.
Hypoxic blackouts
Freedivers are also at risk from pressure on the cardiovascular system which supplies oxygen to vital organs including the brain. If blood oxygen levels get too low, blackouts can happen and may prove fatal if a diver is too deep for quick rescue or has been diving alone (never recommended).
Well-trained divers who have built up competence and experience over time may have higher lung capacity and bodies which use oxygen more efficiently. This enables them to undertake longer, deeper dives with lower chances of blacking out in the water. Beginners should exercise greater caution as they increase the depth and timing of their dives.
Brain damage
While brain cell loss from breath holding seems unlikely, researchers have not ruled out the possibility of long-term cumulative brain damage being triggered by freediving. More research is needed in this area.
Some research has shown that immediately after a breath-hold freedivers may display a transient and minor elevation of a protein associated with brain damage. Levels of this protein were not high enough to suggest actual damage and fell quickly to normal levels but more research is necessary to determine if and how repeated spikes might affect the brain in the long term.
For more information, we’ve written a full article on whether freediving is bad for your brain (opens new tab), which you should find useful.
Decompression sickness
“The bends”, also known as decompression sickness (DCS), can occur in freedivers even though it is not as common as in scuba divers. Very deep dives, longer dives, or multiple dives in a single session could all increase DCS risk. Some people may also naturally have a natural predisposition to DCS.
Measures you can take to reduce your DCS risk include ascending from deep dives at a moderate pace (i.e. 1m/s or less, slowing further during the final 10m); limiting length of session and number of dives; having sufficient recovery time at the surface; staying warm and hydrated; avoiding alcohol and other intoxicants before diving.
Nitrogen narcosis
Another rare but dangerous condition which freedivers might experience is nitrogen narcosis a state of altered consciousness, reduced cognitive function and disrupted neuromuscular control. It is triggered when nitrogen (or other inert gases) enter the bloodstream and reach higher than normal partial pressures at depth.
Nitrogen narcosis may occur from depths of 30-40 meters, or in even shallower water for very sensitive individuals. Serious symptoms could be evident after around 90 meters depth, with the potential for confusion and bad decision-making to result in injury or death without quick intervention.