![]() ![]() At such depths, blood actually penetrated the cell walls of the organs to counteract the external pressure. This shunting is called peripheral vasoconstriction, and it explains how Bucher could dive to below one hundred feet without suffering the lung-crushing effects that Boyle’s law had predicted. Immersion in water triggered the same mechanism in humans. He’d seen the same thing happen in deep-diving seals decades earlier by shunting blood away from less important areas of the body, the seals were able to keep organs like the brain and heart oxygenated longer, extending the amount of time they could stay submerged. Scholander noticed something else: Once his volunteers were underwater, the blood in their bodies began flooding away from their limbs and toward their vital organs. This also explained, to some degree, why Bucher could survive up to three times longer in water than they could in open air: water had some powerful, unknown capacity to slow animals’ hearts. The volunteers’ slower heart rates meant that they used less oxygen and therefore could stay underwater longer. On land, exercise greatly increases heart rate. This discovery was as important as it was surprising. In all cases, no matter how hard the volunteers exercised, their heart rates still plummeted. Next, Scholander told the volunteers to hold their breath, dive down, strap themselves into an array of fitness equipment submerged at the bottom of the tank, and do a short, vigorous workout. From left, swimmer Peter Marshall, Hanli Prinsloo, and the author. We’re able to float at the surface and yet can dive down to great depths while exerting little effort. The human body in its natural form (without weights or wetsuits) is the perfect buoyancy for deep-water diving. Water triggered an immediate decrease in heart rate. He started the experiment by leading volunteers into an enormous water tank and monitoring their heart rates as they dove down to the bottom of the tank. Scholander wondered if water could trigger this effect in humans. ![]() Scholander had seen the biological functions of Weddell seals reverse in deep water the seals, he wrote, actually seemed to gain oxygen the longer and deeper they dove. ![]() In 1962, Per Scholander, a Swedish-born researcher working in the United States, gathered a team of volunteers, covered them with electrodes to measure their heart rates, and poked them with needles to draw blood. Boyle’s law, which science had taken as gospel for three centuries, appeared to fall apart underwater.īoyle’s law, which science had taken as gospel for three centuries, appeared to fall apart underwater.īucher’s dive resonated with a long line of experiments - most of them very cruel and even monstrous by modern standards - that seemed to indicate that water might have life-lengthening effect on humans and other animals. He won the bet, but more important, he proved all the experts wrong. He dove anyway, delivered the package, and returned to the surface smiling, with his lungs perfectly intact. Formulated in the 1660s by the Anglo-Irish physicist Robert Boyle, this equation predicted the behavior of gases at various pressures, and it indicated that the pressure at a hundred feet would shrink Bucher’s lungs to the point of collapse. Scientists warned Bucher that, according to Boyle’s law, the dive would kill him. If he completed the dive, he’d win a fifty-thousand-lira bet if he didn’t, he would drown. Bucher would hand the diver a package, then kick back up to the surface. Waiting there would be a man in a diving suit. Bucher would sail out to the center of the lake, take a breath and hold it, and free-dive down one hundred feet to the bottom. In 1949, a stocky Italian air force lieutenant named Raimondo Bucher decided to try a potentially deadly stunt off the coast of Capri, Italy. Writer James Nestor explores the science of the “mammalian dive reflex,” the phenomenon by which water triggers an immediate decrease in heart rate. Featured image: Photo of freediver Hanli Prinsloo by Annelie Pompe.
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