In August, Natalia Molchanova—a Russian freediver who held 41 world records—dove into the depths of the Mediterranean Sea near Formentera’s La Savina port. The planned dive would take her down of 115 ft, about half the depth of what she dove in Egypt earlier in May. However, she never resurfaced and is now presumed dead.
Dangerous and meditative, freediving is a sport experiencing an unprecedented surge in popularity. The 1988 film “The Big Blue,” which tells the fictionalized version of the rivalry between divers Jacques Mayol and Enzo Maiorca, definitely brought the sport to the mainstream. According to Time, 15 years after the film’s release, the sport grew to around 20,000 competitors.
Researchers from the Univ. of Bonn recently studied the hearts and cardiovascular systems of freedivers in order to understand the effects the taxing sport has on the body. The researchers presented their study recently at the Radiological Society of North America’s annual meeting.
The researchers studied 17 elite divers between the ages of 23 and 58. “To study the effects of lack of oxygen on heart function and blood flow, respectively, the divers underwent cardiac MRI and MRI of the carotid arteries before, during and after a maximum breath hold,” according to the Radiological Society of North America.
The average length of breath-holding during imaging was around 5 min, and the maximal breath-holding time reached was 8 min.
“Prolonged apnea leads to the so-called ‘diving response,’ which included lower heart rate, less blood pumped and contraction of blood vessels in the legs and arms,” said Jonas Doerner, who is currently a radiology resident at the Univ. Hospital of Cologne. This “can burden the heart and lead to significant changes in circulation.”
The researchers witnessed a marked shift of blood flow to the brain, to protect it from lack of oxygen, which was paired with a progressive enlargement and performance reduction of the heart.
“The more blood there is in the brain, the longer the brain can tolerate hypoxia,” said Lars Eichhorn, who was involved in the study and is currently part of the Univ. Hospital of Bonn’s Dept. of Anesthesiology and Intensive Care Medicine.
After some time, the enlarged heart began to lose function as it struggled to pump against the blood vessels’ high resistance. The researchers compared the physiological activity to that seen in systolic heart failure. However, experienced divers were able to overcome the effects after breathing again.
According to Eichhorn, the apnea diving effects are similar to the effects seen in patients with sleep apnea. Going forward, the research team suggested freedivers may be used as models for future sleep apnea studies.