Blue Water Hunting and Freediving - Digital Version 1 - Page 67

freediver physiology
Long Beach Neptunes ’ annual Blue Water Meet , hunting for the largest white seabass .
Ship ’ s Rock is shaped like a pyramid . Its sides consist of large boulders cascading to the sea floor 120 feet below . White seabass cruise near the boulders . Earlier in the day , I shot a 50-pound white seabass . Skip , a fierce competitor , saw my fish and got pumped ! I ’ ll never forget what happened next .
Skip dives to a boulder 50 feet below . He orients himself in the open water and waits … and waits … and waits . I am anxious to take my turn on the rock . Finally , Skip starts his ascent , and I keep his image in the corner of my eye as I start down . Fifteen feet from the surface , he suddenly arches his back , his gun fires and both arms shoot out from his sides . He sinks backward as if impaled on a cross . I drop my gun and angle my dive to intercept Skip . I release his weight belt and , holding Skip around the shoulders , we ascend together .
On the surface , I hold Skip ’ s head clear of the waves . His face is blue-black . I feel he is close to death . His jaws are clenched on his snorkel . With effort , I rip the snorkel from his mouth , and strike him on the chest . “ Breathe !’’ I yell . Skip takes one ragged breath . His next breath returns him to consciousness and he exclaims , “ Hey ! Where ’ s my weight belt ? Where ’ s my gun ?”
Luckily for Skip , he recovered that day without permanent injury . Sixteen years later he realized his goal , spearing a world-record 80-pound white seabass .
THE PHYSIOLOGY OF FREEDIVER BLACKOUT
When I researched the subject of shallowwater blackout for this book , I was shocked to discover that most of the world ’ s top spearfishers have experienced close calls with shallow-water blackout . Damiano Zannini , M . D ., reports that approximately 70 percent of the Italian divers who regularly compete in national and international spearfishing competitions have suffered
Brian Yoshikawa mimics blackout . Photo by Terry Maas one or more blackouts . It ’ s interesting to note that ama divers , with their history of hundreds of years , experience a low rate of shallow-water blackout . They stick to a conservative dive profile by limiting the duration of their dives to one minute and resting between them . They also prefer to make many short dives instead of a few long ones .
The beginning diver is very sensitive to carbon dioxide levels . These levels build even with a breath-hold of 15 seconds , causing your diaphragm to contract involuntarily and your lungs to feel “ on fire .” Normal divers reach their “ breaking point ”— the urge and need to breathe — well before their blood-oxygen levels become dangerously low . Remember , it ’ s not the lack of oxygen , but the rise of carbon dioxide , that signals your brain to breathe .
HYPERVENTILATION : Hyperventilation is the potentially dangerous practice of increasing the rate and / or depth of your breathing in preparation for a dive . Many breath-hold divers reach depths of 80 to 100 feet and achieve bottom times of over two minutes by hyperventilating . The hyperventilating diver has “ blown off ” massive amounts of carbon dioxide , thus outsmarting the brain ’ s breathing center . Normally metabolizing body tissues , producing carbon dioxide at a regular rate , do not replace enough carbon dioxide to stimulate this breathing center until the body is seriously short of oxygen . Trained divers can also shortcircuit the desire to breathe by sheer willpower . Hyperventilation causes some central nervous system changes as well . Practiced to excess , it causes decreased blood flow to the brain , dizziness , and muscle cramping in the arms and legs . But moderate degrees of hyperventilation can cause a state of euphoria and well-being . This can lead to overconfidence and the dramatic consequence of a body performing too long without a breath : blackout .
The use of hyperventilation in preparation for freediving is controversial . No one disagrees that prolonged hyperventilation , after minutes of vigorous breathing accompanied by dizziness
61