Croatian Vitomir Maričićin June 2025, set a record that appears to defy biology: 29 minutes And 3 seconds holding your breath underwater. How is it possible to push the human body so far? We asked the Dr. Pasquale LongobardiVice President of the Italian Society of Underwater and Hyperbaric Medicine (SIMSI) and Medical Director of the Hyperbaric Center of Ravenna, to reveal the science behind this enterprise at the frontiers of physiology. Freediving consists of diving while holding your breath, without the aid of tanks. Often perceived as an extreme sport, it is actually a widespread discipline in Italy, with specialties that adapt to different objectives and environments. It goes fromstatic apnea (stay still in one place in the pool)dynamic apnea (travel the maximum distance underwater, with or without fins, always in the pool). In open waters (sea or lake), the challenge shifts to depth, with disciplines such astoconstant setup (descent and ascent with one’s own strength) and the jump blue.
Practicing freediving safely requires specific training and medical checks quotes. Behind the extreme feats of professionals like Vitomir Maričić, there is a huge physical and mental preparationflanked by a specialist medical monitoring. With Dr. Longobardi we analyzed exactly what happens to the human body when it pushes beyond the limits of breathing and how freedivers train.
To begin, can you help us understand the fundamental difference between this extreme performance, which involves pre-inhalation of oxygen, and a traditional air freedive?
Yes, Vitomir Maričić’s record seems to defy biology: 29 minutes and 3 seconds of static apnea, obtained after 10 minutes of pre-oxygenation with pure oxygen. What we see is not a magic trick, but the ability to bring the body into a state of “commanded survival”where the heart, brain and lungs work at the bare minimum. It is a real journey to the neurophysiological limit, where the mind controls the body.
Traditional freediving is done by breathing normal air, while these extreme performances use 100% oxygen to “charge” the body. With the evolution of techniques and the understanding of physiology, the limits have moved enormously in all freediving disciplines: just think that in the 1960s it was considered impossible to exceed 30 meters of depth, while today they exceed 200 metres.
What happens to our body during an apnea?
Our organism has gods automatic reflexes very powerful that are activated every time we immerse our face in water, even in a simple basin. The autonomic nervous system triggers thecentral blood flow, the famous “blood shift”. The blood is “stolen” from the peripheries (arms, legs) and conveyed towards the vital organs, a bit like a Robin Hood physiological that takes oxygen where it is least needed to give it to the heart and brain. This also causes the peripheral vasoconstriction and ensures that the chest, even at great depths, is filled with blood (being an incompressible liquid), resisting crushing.
At the same time, the arrival of more blood to the heart slows down its beating, which can drop to 30 per minute, in the condition called bradycardia. It is an incredible protection mechanism, studied since the times of Enzo Maiorca – the first man to cross the threshold of 100 meters of depth in freediving – with experiments in hyperbaric environments. The spleen also plays an important role by contracting and releasing red blood cells to increase available oxygen.
In addition to these natural reflexes, professional freedivers also use technical “tricks”, such as glossopharyngeal compensation or “carp technique”: the athlete “gasps” to take in air with his mouth closed and then “plungers” it into the lungs with his tongue, increasing the volume of air stored. It is an effective technique, but not recommended by doctors because it can cause micro-lesions to the pulmonary alveoli or in more serious cases pulmonary edema (excess fluid in the lungs).
Speaking of risks, what are they and what should anyone who wants to take up this sport know?
In addition to physiological mechanisms, apnea also comes into play risks and the individual genetic predisposition. One of the dangers is theimmersion pulmonary edema (IPE), an accumulation of fluid in the alveoli caused by strong pressure differences. Not everyone reacts the same way, and the genetics plays an important role.
For example, some variants of specific genes, i polymorphismscan increase vulnerability. One of these concerns the enzyme nitric oxide synthase: nitric oxide (NO) is a fundamental molecule that our body produces, for example at night, to “clean” blood vessels, like garbage trucks. Those who produce less nitric oxide (some genetic variants produce up to three times less than average) may have less efficient blood flow regulation, potentially increasing the risk of cerebrovascular accidents in extreme conditions.
Other variations to better understand the individual response to deep apnea and its risks concern theACE (angiotensin converting enzyme), which regulates the caliber of blood vessels and is therefore crucial for the effectiveness of blood shiftThe hypoxia-induced factor (HIF-1α) and predisposition to thrombophilia (tendency to form clots).
From a clinical point of view, what are the most common emergencies that a doctor faces?
When oxygen reserves fall below safe levels during freediving, the most serious risks arise. There syncope is an example of this, the brain, deprived of oxygen, loses consciousness. It is often preceded by “Samba”a loss of motor control in which the athlete is still conscious but no longer coordinates movements. I had direct experience of this in the 90s, during a rescue in Ustica I carried out a ventilation in the water. The freediver had surfaced in Samba, I dived to assist him with artificial ventilation. The absence of immediate and expert assistance inevitably leads to drowning.
In summary, the freediver experiences a silent battle between mental calm and physiological chaos.
Freediver training: how does an athlete train to prepare his body and mind for such an undertaking? What kind of physical and mental preparation is behind these records?
Elite freedivers train the mind with the same intensity with which they train the body. They learn to manage panic, slow down their thoughts and remain still even when their instincts scream to breathe. Techniques like meditationthe mindfulnessthe pranayama breathing and the mental visualization are fundamental and help to keep the heartbeat slow, reduce cortical activity and, consequently, the oxygen consumption. A calm brain, in fact, can consume up to 20-30% less O₂ compared to a state of alert.
This mental work is accompanied by a solid one physical preparationwhich includes a aerobic training aimed at optimizing cardiovascular efficiency. It’s a real one neurophysiological training: you learn to ‘trick’ the breathing centers in the brainstem, delaying the sensation of air hunger. This is a conscious control of the autonomic nervous system, supported by a body conditioned to use oxygen as efficiently as possible.
Why does breathing pure oxygen before freediving allow you to hold your breath longer? How exactly does it work and what advantage does it provide?
There pre-oxygenation is the key to records like that of Maricic, the athlete breathes pure oxygen for approximately 10 minutes before the dive. This technique not only serves to fill the lungs, but acts on a cellular level, “charging” the mitochondriaour energy plants. Each cell of the heart, for example, contains approximately 5000. They work like small batteries, maintaining a potential difference of approx 180 millivolts (mV) thanks to oxygen; if this potential falls below i 70 mVthe cell can undergo apoptosis, i.e. programmed death.
Hyperoxygenation “charges” these mitochondria, allowing them to produce more ATP – our energy “petrol”, we regenerate approximately 50 kg per day – and to do it more efficiently. Oxygen is also stored in molecules such as phosphocreatine and the myoglobin muscle, increasing the resistance to hypoxia of vital organs such as the brain and heart.
Studying this reaction helps us understand how to support the body in critical situations such as head trauma, stroke, decompression accidents, or even in space missions and underwater habitats. It’s a way to explore the limits of the human body.
Pre-inhalation of oxygen also has risks, what are they?
Oxygen toxicity is a risk in freediving with pre-oxygenation, especially because the amount of oxygen in the body depends on pressure and therefore depth. Too much can lead to physiological problems, such as seizures in the Paul Bert effect. For this reason, some studies suggest waiting 10-15 minutes after pre-oxygenation before diving, although Maričić dived right away.
Is pre-oxygenation a practice accepted by the Federations regarding records?
These records of extreme apnea, obtained with pre-inhalation of oxygen, in reality they are not recognized by official sports federations like FIPSAS or AIDA. They are companies that focus more on Guinness World Records and are often supported by private sponsorships.
However, precisely because they are performances at the limits, these athletes are constantly followed by specialized medical teams. This continuous monitoring allows you to collect valuable data and do scientific researchhelping us to better understand how the human body reacts to such extreme conditions.
How much of Maričić’s record is due to physical training and how much to mental training and body control?
Extreme freediving is 50% physiology and 50% psychology. The body adapts, but it is the mind that decides how far you can go.
From your expert point of view, after seeing such records, where is the true human limit in this discipline? Is it more a structural limit of our body or of our ability to “hack” our own physiology?
The human limit in freediving is not written in the lungs, but in the mind. The body has clear boundaries – blood pressure, lung capacity, oxygen saturation – but the brain can shift the breaking point. Neurophysiology studies show that experienced freedivers can maintain calm and clarity even in conditions of cerebral hypoxia, modulating the activity of the limbic system and the response to stress. When the brain is ‘not afraid’, it consumes less oxygen and gains time. Maričić proved it: after 10 minutes of pre-oxygenation, he lasted 29 minutes and 3 seconds in apnea, not only thanks to biology, but to the mental ability to stay in absolute silence. Ultimately, extreme freediving is not a race against time, but against themselves.
Every record under water teaches us something about how in the silence of the water, the mind wins where the body stops. The freediver’s motto is “breathe deeply first and then let the silence speak”.
