The science behind a freediver’s 29-minute breath hold world record

Croatian freediver Vitomir Maričić. Facebook.com @molchanovs, Instagram.com @maverick2go, Facebook.com @Vitomir Maričić, CC BY 

Theresa Larkin, University of Wollongong and Gregory Peoples, University of Wollongong

Most of us can hold our breath for between 30 and 90 seconds.

A few minutes without oxygen can be fatal, so we have an involuntary reflex to breathe.

But freediver Vitomir Maričić recently held his breath for a new world record of 29 minutes and three seconds, lying on the bottom of a 3-metre-deep pool in Croatia.

Vitomir Maričić set a new Guinness World Record for “the longest breath held voluntarily under water using oxygen”.

This is about five minutes longer than the previous world record set in 2021 by another Croatian freediver, Budimir Šobat.

Interestingly, all world records for breath holds are by freedivers, who are essentially professional breath-holders.
They do extensive physical and mental training to hold their breath under water for long periods of time.

So how do freedivers delay a basic human survival response and how was Maričić able to hold his breath about 60 times longer than most people?

Increased lung volumes and oxygen storage

Freedivers do cardiovascular training – physical activity that increases your heart rate, breathing and overall blood flow for a sustained period – and breathwork to increase how much air (and therefore oxygen) they can store in their lungs.

This includes exercise such as swimming, jogging or cycling, and training their diaphragm, the main muscle of breathing.

Diaphragmatic breathing and cardiovascular exercise train the lungs to expand to a larger volume and hold more air.

This means the lungs can store more oxygen and sustain a longer breath hold.

Freedivers can also control their diaphragm and throat muscles to move the stored oxygen from their lungs to their airways. This maximises oxygen uptake into the blood to travel to other parts of the body.

To increase the oxygen in his lungs even more before his world record breath-hold, Maričić inhaled pure (100%) oxygen for ten minutes.

This gave Maričić a larger store of oxygen than if he breathed normal air, which is only about 21% oxygen.

This is classified as an oxygen-assisted breath-hold in the Guiness Book of World Records.

Even without extra pure oxygen, Maričić can hold his breath for 10 minutes and 8 seconds.

Resisting the reflex to take another breath

Oxygen is essential for all our cells to function and survive. But it is high carbon dioxide, not low oxygen that causes the involuntary reflex to breathe.

When cells use oxygen, they produce carbon dioxide, a damaging waste product.

Carbon dioxide can only be removed from our body by breathing it out.

When we hold our breath, the brain senses the build-up in carbon dioxide and triggers us to breathe again.

Freedivers practice holding their breath to desensitise their brains to high carbon dioxide and eventually low oxygen. This delays the involuntary reflex to breathe again.

When someone holds their breath beyond this, they reach a “physiological break-point”. This is when their diaphragm involuntarily contracts to force a breath.

This is physically challenging and only elite freedivers who have learnt to control their diaphragm can continue to hold their breath past this point.

Indeed, Maričić said that holding his breath longer:

got worse and worse physically, especially for my diaphragm, because of the contractions. But mentally I knew I wasn’t going to give up.

Mental focus and control is essential

Those who freedive believe it is not only physical but also a mental discipline.

Freedivers train to manage fear and anxiety and maintain a calm mental state. They practice relaxation techniques such as meditation, breath awareness and mindfulness.

Interestingly, Maričić said:

after the 20-minute mark, everything became easier, at least mentally.

Reduced mental and physical activity, reflected in a very low heart rate, reduces how much oxygen is needed. This makes the stored oxygen last longer.

That is why Maričić achieved this record lying still on the bottom of a pool.

Don’t try this at home

Beyond competitive breath-hold sports, many other people train to hold their breath for recreational hunting and gathering.

For example, ama divers who collect pearls in Japan, and Haenyeo divers from South Korea who harvest seafood.

But there are risks of breath holding.

Maričić described his world record as:

a very advanced stunt done after years of professional training and should not be attempted without proper guidance and safety.

Indeed, both high carbon dioxide and a lack of oxygen can quickly lead to loss of consciousness.

Breathing in pure oxygen can cause acute oxygen toxicity due to free radicals, which are highly reactive chemicals that can damage cells.

Unless you’re trained in breath holding, it’s best to leave this to the professionals.

Theresa Larkin, Associate Professor of Medical Sciences, University of Wollongong and Gregory Peoples, Senior Lecturer - Physiology, University of Wollongong

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Read More........→September 12, 2025

World’s Smallest Pacemaker is Made for Newborns, Activated by Light, and Requires No Surgery

World’s smallest pacemaker next to a grain of rice – Credit: John Rogers / Northwestern University press release

Northwestern University engineers have developed a pacemaker so small that it can fit inside the tip of a syringe and be non-invasively injected into the body, according to a new study published in Nature.

Although it can work with hearts of all sizes, the pacemaker is particularly well-suited to the tiny, fragile hearts of newborn babies with congenital heart defects.

A pacemaker is an implantable device that helps maintain an even heart rate, either because the heart’s natural cardiac pacemaker provides an inadequate or irregular heartbeat, or because there is a block in the heart’s electrical conduction system.

Smaller than a single grain of rice, the pacemaker is paired with a small, soft, flexible, wireless, wearable device that mounts onto a patient’s chest to control pacing. When the wearable device detects an irregular heartbeat, it automatically shines a light to activate the pacemaker.

These short light pulses, which penetrate through the patient’s skin, breastbone, and muscles, control the pacing.

Designed for patients who only need temporary pacing, the pacemaker simply dissolves after it’s no longer needed. All the pacemaker’s components are biocompatible, so they naturally dissolve into the body’s biofluids, bypassing the need for surgical extraction.

The paper demonstrates the device’s efficacy across a series of large and small animal models as well as human hearts from deceased organ donors.

“We have developed what is, to our knowledge, the world’s smallest pacemaker,” said John A. Rogers, PhD, professor of Neurological Surgery, Dermatology, and in the McCormick School of Engineering, who led the device development.

“There’s a crucial need for temporary pacemakers in the context of pediatric heart surgeries, and that’s a use case where size miniaturization is incredibly important. In terms of the device load on the body—the smaller, the better.”

“Our major motivation was children,” said Igor Efimov, PhD, professor of Medicine in the Division of Cardiology and in the McCormick School of Engineering, who co-led the study.

“About 1% of children are born with congenital heart defects, regardless of whether they live in a low-resource or high-resource country. The good news is that these children only need temporary pacing after a surgery. In about seven days or so, most patients’ hearts will self-repair. But those seven days are absolutely critical. Now, we can place this tiny pacemaker on a child’s heart and stimulate it with a soft, gentle, wearable device. And no additional surgery is necessary to remove it.”

This work builds on a previous collaboration between Rogers and Efimov, in which they developed the first dissolvable device for temporary pacing. Many patients require temporary pacemakers after heart surgery — either while waiting for a permanent pacemaker or to help restore a normal heart rate during recovery.

For the current standard of care, surgeons sew the electrodes onto the heart muscle during surgery. Wires from the electrodes exit the front of a patient’s chest, where they connect to an external pacing box that delivers a current to control the heart’s rhythm.

When the temporary pacemaker is no longer needed, physicians remove the pacemaker electrodes. Potential complications include infection, dislodgement, torn or damaged tissues, bleeding, and blood clots.

“That’s actually how Neil Armstrong died,” Efimov said. He had a temporary pacemaker after a bypass surgery. When the wires were removed, he experienced internal bleeding.”

In response to this clinical need, Rogers, Efimov, and their teams developed their first dissolvable pacemaker, which was introduced in Nature Biotechnology in 2021. The thin, flexible, lightweight device eliminated the need for bulky batteries and rigid hardware, including wires.

To help further reduce the device’s size, the researchers also reimagined its power source. Instead of using near-field communication to supply power, the new, tiny pacemaker operates through the action of a galvanic cell, a type of simple battery that transforms chemical energy into electrical energy. Specifically, the pacemaker uses two different metals as electrodes to deliver electrical pulses to the heart. When in contact with surrounding biofluids, the electrodes form a battery. The resulting chemical reactions cause the electrical current to flow to stimulate the heart.

“When the pacemaker is implanted into the body, the surrounding biofluids act as the conducting electrolyte that electrically joins those two metal pads to form the battery,” Rogers said. “A very tiny light-activated switch on the opposite side from the battery allows us to turn the device from its ‘off’ state to an ‘on’ state upon delivery of light that passes through the patient’s body from the skin-mounted patch.”

The team used an infrared wavelength of light that penetrates deeply and safely into the body. If the patient’s heart rate drops below a certain rate, the wearable device detects the event and automatically activates a light-emitting diode. The light then flashes on and off at a rate that corresponds to the normal heart rate.

“Infrared light penetrates very well through the body,” Efimov said. “If you put a flashlight against your palm, you will see the light glow through the other side of your hand. It turns out that our bodies are great conductors of light.”

Even though the pacemaker is so tiny—measuring just 1.8 millimeters in width, 3.5 millimeters in length and 1 millimeter in thickness—it still delivers as much stimulation as a full-sized pacemaker.“The heart requires a tiny amount of electrical stimulation,” Rogers said. “By minimizing the size, we dramatically simplify the implantation procedures, we reduce trauma and risk to the patient, and, with the dissolvable nature of the device, we eliminate any need for secondary surgical extraction procedures.” World’s Smallest Pacemaker is Made for Newborns, Activated by Light, and Requires No Surgery

Read More........→April 09, 2025