>during Deja Blue 8 in the Cayman Islands.
>Meanwhile, technical diving's edgy cousin, breath-hold diving (or freediving), is redefining the limits of apneic divers and in the process raising new, unanswered questions about diving physiology.
>Today freedivers routinely push to (or beyond) technical-diving depths, sometimes within a few years or even months of beginning their training, and new techniques and adapted technologies such as nitrox promise to push the envelope even further. "There's no baseline data, which makes freediving a bit of a Wild West," observed Drew Richardson, CEO of the Professional Association of Diving Instructors (PADI). "It's definitely the pointy end of diving."
>Freediving has been quietly gaining momentum through the pioneering work of organizations such as Performance Freediving International (PFI), the oldest breath-hold training agency in North America, founded in 2000 by former technical-diving instructor trainer Kirk Krack. In the past few years, however, PADI, SSI, the rebreather association RAID and the National Association of Underwater Instructors (NAUI) have introduced freediving programs that have helped push the sport to a tipping point. The result: Freediving is now the fastest-growing segment of diving and is attracting a new audience of people who love the water and are into fitness, self-improvement and mind-body awareness — in addition to the largely self-taught spearfishing community. Even so, most scuba divers have little knowledge of what may ultimately become the predominant form of diving.
>While tech diving depends on technology to take us where few have gone before, freediving focuses on our innate diving ability. As such, it represents a new frontier in underwater exploration: rediscovering and engaging our genomic inheritance — our inner marine mammal.
>Channeling Your Inner Marine Mammal
>That isn't hyperbole. Research conducted by Erika Schagatay, Ph.D., and colleagues concluded that humans share the physiological adaptions found in aquatic and semiaquatic mammals.1 These include naked skin, a layer of subcutaneous fat, the ability to equalize ears and sinuses, underwater vision, effective locomotion, the diving response (in which blood is shunted to protect the lungs) and a recently discovered "spleen response" similar to that found in seals, which increases our blood's oxygen-carrying capacity when triggered (and suggests that we share an aquatic prehistory).
>Schagatay's further research has shown that as little as a week of training can significantly improve breath-hold times, diving response and hemoglobin concentration.2 Her conclusions are not lost on freediving aficionados who treat training as a lifestyle — in the water and out — quieting the mind, stretching, practicing proper breathing techniques, conducting hypoxia and hypercapnia exercises, perfecting their form and learning to listen to their bodies, all of which makes apnea training more yoga than Ironman. In addition, their working knowledge of diving physiology is impressive; they're as geeky as any tech diver.
>Competition is a unique aspect of freediving that leads apneists to hone and test their skills with respect to depth, distance and time. Last year 240 such contests were held under the auspices of the International Association for the Development of Apnea (AIDA), the world rules- and record-keeping body for breath-hold competitions, and only four of those were in the U.S. These are treated as celebrations by the apneic diaspora, and everyone is supportive.
>Freediving disciplines include deep diving (descent with or without fins or by pulling oneself down a line), dynamic apnea (horizontal distance swimming underwater with or without fins) and static apnea (timed breath-holds at the surface). While competitive events tend to be extreme in nature — top divers can attain depths of 70-120 meters (230-400 feet), swim 150-300 meters (500-1,000 feet) horizontally underwater and hold their breath for 5-11 minutes — a typical day of freediving might involve making 30-50 dives in a kelp forest or on a reef or shipwreck at depths of 10-30 meters (30-100 feet).
>Blackouts and near-blackouts, though rare, are the primary safety concern in freediving: 99 percent occur shallower than 5 meters (16 feet) — 90 percent happen on the surface, and 9 percent occur between 5 meters (16 feet) and the surface. (In competition, 1 in 20 dives might end up as a blackout or near-blackout — at the surface or at depth.) Accordingly, the primary rule of freediving is always dive under the direct supervision of a buddy who can rescue you.
>For a two-person team this typically takes the form of "one buddy up, one buddy down." As an additional precaution, divers weight themselves to be neutral at 10 meters (33 feet) so they will float to the surface should a blackout occur. Fatalities are rare when protocols are followed.
>Deep divers also risk lung and trachea squeezes, which are characterized by blood in the mouth or nose upon surfacing — and these injuries may be on the rise. "In the past, people took a long time to get to depth. Today they are jumping to big depths in months as a result of the Frenzel and mouthfill equalization techniques, but they may need more adaption," explained PFI instructor Kerry Hollowell, M.D. "In fact, we may be overdiving some of the adaptions that protect us. We just don't know." Apneists can also suffer ruptured eardrums, but this tends to happen to newer divers who "ride their ears."
>Decompression sickness (DCS) is a rarity, though it can occur in the case of repetitive deep dives, such as those conducted by freediving's unsung heroes: competition safety divers. Unfortunately, no one knows exactly where the limits are. As one scientist put it, "Freediving is currently a data-free zone."
>Perhaps the most exciting new development in freediving is prebreathing nitrox to extend bottom times or breathing 100 percent oxygen postdive to shorten surface intervals and protect against DCS. Krack and his team provide predive nitrox and postdive oxygen to safety divers at PFI's annual Deja Blue competition, which is regarded as the sport's most sophisticated operation. PFI also uses nitrox to extend dive times — conducting, for example, 40-meter (130-foot) dives with three- to six-minute (and longer) bottom times during their recent Truk expedition, in what Krack calls "technical freediving."
>Back to the Future
>Former world-record holder Eric Fattah, who invented the Liquivision F1 freediving computer, fluid goggles and the mouthfill technique, which enables divers to equalize at deep depths, is also an advocate of nitrox, which he has been using for freediving since 2009. Fattah is convinced that prebreathing nitrox not only increases bottom time but also can practically eliminate the risk of hypoxia.
>Currently there are no studies to delineate a freediving central nervous system (CNS) clock or oxygen tolerance unit (OTU) table. "It's like the early days of tech diving," Richardson said. "These are passionate adventurers operating by the seat of their pants and some theory. They're the tip of the spear."
>1. Schagatay E. Human breath-hold diving ability and its underlying physiology. Human Evolution 2014; 29(1-3):125-140. Available at: miun.diva-portal.org/smash/get/diva2:681668/FULLTEXT01.pdf
>2. Sahlin L, Krohn T, Sedin M, Schagatay E. Effects of one week of daily apnea training in humans. Abstract of Undersea and Hyperbaric Medical Society Meeting Paper 2000. Available at: archive.rubicon-foundation.org/xmlui/handle/123456789/6741
>Watch freediver Kirk Krack tour the Nippo Maru wreck in Truk Lagoon — all on one breath.
>© Alert Diver — Q4 Fall 2017