Asked by: Jason Woods, Dover Show In all mammals, including humans, a dive reflex is activated when the face is submerged. The heart rate slows, and blood flow is diverted away from the limbs towards the head and torso. In aquatic mammals, this reflex is particularly well-developed. Without training, we can manage about 90 seconds underwater before needing to take a breath. But on 28 February 2016, Spain’s Aleix Segura Vendrell achieved the world record for breath-holding, with a time of 24 minutes. However, he breathed pure oxygen before immersion. Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.
As a parent, I often find myself asking questions I never thought I would ask: How long can someone survive on raisins alone? How did that yogurt get on the ceiling? And so one night, after carefully placing my sleeping baby down in his crib, I stood there holding my breath, noting that I would obviously choose passing out over possibly making the slightest sound that could wake him. I wondered, How long can a person’s body go without oxygen? What sets that limit and why is it that some people can hold their breath for minutes but others only seconds? To set the Guinness World Record for breath-holding, a professional freediver went without breath for a whopping 24 minutes and 3 seconds. The Guinness World Record for the longest time spent holding one’s breath was set in 2016 by Aleix Segura Vendrell in a pool in Spain. The professional freediver went without breath for a whopping 24 minutes and 3 seconds. Before Vendrell, a record was set just two years earlier in 2014 by Danish freediver Stig Severinsen at 22 minutes. Those numbers are more than 40 times longer than the 30 seconds or so that the average person goes before coming up for air. Compare that to the fastest mile-run on record at an impressive 3 minutes and 43 seconds which is only 3-4 times shorter than the more average pace of a 12-minute mile. Hyperventilating allows you to hold your breath longerWhen you hold your breath, it’s not actually the lack of oxygen that does you in, but the excess of carbon dioxide that is not getting exhaled. When CO2 builds up in your body, your blood will acidify as your enzymes convert water and the excess CO2 into carbonic acid. This acidification can lead to drowsiness and headaches and ultimately have a detrimental effect on the body’s major organs. One way record-breaking breath-holders manage such long stints under water is to breathe pure oxygen (basically hyperventilate) before their diving attempt. So one way record-breaking breath holders manage such long stints under water is to breathe pure oxygen (basically hyperventilate) before their diving attempt. This rids their lungs of as much CO2 as possible. If you take a deep breath right now and try to hold it, you may notice that exhaling a bit helps you hold it longer. Throughout Vendrell’s 24 minutes, the oxygen in his lungs got picked up by his bloodstream to be distributed to his vital organs. Without oxygen and without CO2, his lungs were empty so he was able to stay under and only inhaled deeply after rising above the surface. Does lung capacity set a limit on breath-holding?This suggests that lung volume or capacity may set a mechanical limit on breath-holding. So those with longer torsos may be at an advantage. Men also have higher lung capacities than women by 10-12% likely due to larger on average rib cages. Lifestyle choices like not smoking and endurance training can increase your lung capacity, but usually only by incremental amounts. Freedivers employ a technique called lung packing that can double or even triple your lung capacity. When lung packing, you fill your lungs with air but then continue to take smaller breaths, effectively forcing them down into your already full lungs and training your lungs to hold more air. However, it’s not all mechanics. Your metabolic rate does factor into how long you can hold your breath. That’s why record-setting breaths are taken while floating in a pool and not while someone is actively swimming or diving. The limit may be psychologicalHowever, even given extensive training and massive lung capacities, researchers still don’t see a clear explanation for how someone can manage going over 20 minutes without air and suggest that it can’t be all physiology. There must be some form of mind-over-matter involved. All mammals have what is called a dive reflex which causes our hearts to slow down when we submerge our bodies or even just our faces in cold water. This reflex is why these long stints of breath-holding happen in pools. Our blood gets redirected from our neglectable extremities to focus instead on our more important organs like the brain, heart, and lungs. The dive reflex has saved the lives of more than a few people who have fallen into icy water for several minutes before being rescued. All mammals have what is called a dive reflex which causes our hearts to slow down when we submerge our bodies or even just our faces in cold water. So what does a reflex have to do with psychology? Many freedivers describe entering a calm and meditative state as a key tool for holding their breath for extended periods. They are able to extend the same benefits of this dive reflex through training and practice. Another huge psychological factor is overcoming the urge to breathe. It sounds simple, but our instinct, luckily, is survival. So the urge to breathe—that chemical signal our body sends to the brain screaming “I need air!”—may be more important in sending us back to the surface gasping for air than the actual need to breathe. Freedivers like Vendrell describe fighting that urge as a key tool for keeping themselves underwater. So scientists don’t yet understand what exactly sets the human body’s limit on holding its breath, but it is likely a complex combination of mechanical, metabolic, and psychological factors. Advances in pushing the known limit appear to progress similarly to other feats of athletic prowess, that is, not linearly. In other words, each new record no longer doubles or triples the previous one, but instead advances appear to be leveling off and becoming more incremental with each new record-setting breath. And if you’ve held your breath throughout this entire podcast, congratulations—you only have to extend that by about four more times to be the next record-holder!
While some studies say most people can hold their breath for 30 seconds to maybe a few minutes at most, Aleix Segura Vendrell of Spain, the most recent Guinness World Record holder, held his for an astonishing 24 minutes and 3 seconds while floating in a pool in Barcelona. Don’t feel ashamed if you can’t even approach Segura Vendrell’s pulmonary prowess. The ability to hold your breath is hardwired. Segura Vendrell achieved the record with the help of what is known as an oxygen-assist. He breathed pure oxygen for a certain period of time before he began his extended float—essentially hyperventilating, filling his lungs to capacity with oxygen. Lung function—and breath holding—varies widely from individual to individual, says Clayton Cowl, chair of preventive occupational and aerospace medicine at the Mayo Clinic in Rochester, Minnesota. Body types and gender can influence lung function. For instance, studies have shown that people with shorter trunks tend to have lower lung function than those with longer trunks. Women have lung volumes that are 10 to 12 percent less than men, because their rib cages are usually smaller. During the normal breathing process, oxygen is taken in and carbon dioxide is exhaled. The process is automatic, occurring thousands of times a day. Holding the breath causes carbon dioxide, which is essentially a waste product, to accumulate with nowhere to go. The longer the hold, the more likely the person will experience strong and painful spasms of the diaphragm and in the muscles between the ribs as carbon dioxide builds up in the blood. The breath holder becomes lightheaded. High carbon dioxide levels—not low oxygen—account for the symptoms experienced by breath holding, says Cowl. “It’s like a carbon dioxide narcosis,”—an almost narcotic-like state, he says. The parameters of breath holding are primarily dictated by hard-wired processes, according to Cowl. Chemical receptors in the brain’s medulla oblongata (a part of the brain stem) act in a manner similar to the thermostat for a central cooling system. When carbon dioxide reaches a certain level in the blood stream, the receptors “trigger the brain to say ‘I need to breathe,’” Cowl says. Another innate process is the Hering-Breuer reflex, which helps prevent over inflation of the lungs. A deep breath triggers the reflex, causing certain stretch receptors in the lungs to fire. The receptors send signals to the brain’s respiratory center telling it to suppress breathing—because you’ve already taken a breath. But psychology plays a crucial role as well. “You can voluntarily say ‘I’m going to hold my breath longer than a usual breath,’ and by doing so, you can train yourself to do longer and longer breath holds,” Cowl says. That seems to be how people like Segura Vendrell, who is a diver, and other people who engage in free diving, appear to be able to hold their breath for especially long periods of time—four to eight minutes or more, even without breathing oxygen beforehand—while they descend to depths of up to 700 feet. This is a trained voluntary response, says Cowl, but “on a cellular level, it’s not clear how someone physiologically is able to do this.” He suspects it may mean the divers are “mentally tolerating the symptoms longer.” Olympic swimmers seem to be able to go great distances without breathing, but that is primarily due to aerobic conditioning, says Cowl. Those athletes are more efficient at getting oxygen into the tissue and extracting carbon dioxide. That allows them to breathe more effectively, and potentially, improve their breath holding. Just being in the water may confer additional breath-holding ability. All mammals have what is known as a diving reflex. The involuntary reflex is most obvious—and pronounced—in aquatic mammals like whales and seals. But humans have this reflex, also. The purpose seems to be to conserve the oxygen that is naturally stored throughout the body, according to one study. When a mammal dives into the water, the heart rate slows, and the capillaries of extremities like arms and legs—or flippers—constrict. Blood and oxygen is redirected towards the internal organs. The reflex helps diving animals override the need to breathe, which means they can stay underwater longer. It is not clear why the reflex developed, but further understanding could extend the boundaries of human performance. |