The Big Blue Physiological Adaptation to Habitual Breath Hold Diving Is Inconclusive and It Is P Mccrory More Likely That the Psychological Desire
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EDITORIAL 1 Br J Sports Med: first published as 10.1136/bjsm.37.1.1 on 1 February 2003. Downloaded from Warm up important metabolic and other circula- ................................................................................... tory physiological changes that character- ise the full diving reflex in diving mam- mals. The evidence that there is a The Big Blue physiological adaptation to habitual breath hold diving is inconclusive and it is P McCrory more likely that the psychological desire ................................................................................... to override the “break point is the primary change. Presumably this is how the Ama and other people around the world in- volved in diving for sponges or pearls achieve their performance n October 2002, Audrey Mestre both Mestre was attempting a no limit Animals such as deep diving whales set a world record for free diving and world record in the ocean off the died in an attempt to extend it further. Dominican Republic, having completed a and the physiologically remarkable I Weddell seal (23 minute dives at 230 This extreme sport is fascinating for practice dive to the remarkable depth of sports physicians as it represents a very 171 metres. This performance was post- metres have been recorded!) have a practical demonstration of pulmonary humously recognised by the IAFD as a number of physiological adaptation that physiology. new world record. In her formal record mean that their performance is achieved Free diving was made popular by the attempt she reached the depth of 171 with minimal or no lung volume and 1988 French film, The Big Blue, which was metres after 1 minute and 42 seconds without the risk of inert gas narcosis inspired by real events and featured and then attempted to inflate the air bag. or decompression sickness. Terrestrial spectacular underwater cinematography. The circumstances after this stage are animals, including humans are mostly Currently there are more than 20 000 unclear but her ascent was delayed. She limited by oxygen stores that mean the free divers worldwide and the numbers was pulled from the water after 8 risk of “shallow water” blackout is are growing. The International Associ- minutes and 40 seconds by her husband extremely high during ascent from ation of Free Divers (IAFD) based in (also a noted free diver and holder of the breath hold diving as the arterial oxygen Miami, USA oversees the sport and former world record of 162 metres set in saturation drops below the critical certifies world records. January 2000). Attempts to revive her threshold for consciousness, which is in Most free divers use the “constant bal- failed and an autopsy noted the cause of the range of 25–30 mm Hg. Hyperventi- last” technique in which divers use fins death as drowning. lation prior to a breath hold dive but no extra weights to dive as deep as IAFD President, Carlos Serra who was increases this risk as the respiratory possible before coming up for air. “No present at the record attempt, claimed drive is diminished. Because of the rapid limit” free divers take it further by using a that the airbag failed to inflate properly drop in arterial oxygen at the tail of the metal sled (weighing 90kg) that slides and Mestre appears to have become oxygen dissociation curve, the margin of down a vinyl coated steel cable. When the unconscious at 121 metres and fallen diver wishes to ascend, he or she releases from her sled. A video camera was safety is extremely narrow resulting in an airbag at the top of the sled that shoots apparently attached to the sled to record an often fatal shallow water blackout the diver back to the surface. Due to the the attempt, however the video footage despite achieving phenomenal physio- http://bjsm.bmj.com/ relatively short submersion time, decom- from this has not been released. logical performance. pression sickness is not normally a prob- This sport demonstrates the envelope Although the remarkable record lem although the effects of rapid pressure of human performance that is achievable achieved by Mestre demonstrates the changes on air-fluid interfaces in the body in a hostile environment. Man is poorly envelope of physiological performance may result in the same spectrum of prob- adapted for diving, relying principally on fairly dramatically, I have no doubt that lems seen in compressed air divers. Fewer lung oxygen stores during breath hold other free divers will attempt to break it. than two dozen elite athletes compete in diving. The diving bradycardia that ac- Such is life. the “no limit” extreme category attempt- companies this process (Mestre’s heart on September 29, 2021 by guest. Protected copyright. ing to push the boundary of human rate at 171 metres was apparently 20 beats performance ever further. per minute) is not accompanied by the Br J Sports Med 2003;37:1 www.bjsportmed.com.