During his career, Umberto Pelizzari set several world records in all three categories of deep freediving - constant weight freediving (in which the diver descends and ascends using their monofin, and without pulling on the rope or changing their ballast), variable weight freediving (which involves descending with weight, and ascending without by pulling on the rope or finning) and no limits freediving, the deepest discipline of all (with a sled or ballast weight to make a rapid descent, and ascent with the help of a buoyancy device). Pelizzari free-dived competitively from the late 1980’s to 2001, when he retired from competition. In the Seventies, the two top Italian freedivers Enzo Maiorca and Jacques Mayol held and broke the freediving world records, helping to break freediving into the mainstream. There weren't many people freediving in those days. In Italy, there was an ongoing battle between the Sicilian and Tuscan diving fraternities, each of whom had enormous love and respect for the sea.
Anyone who did freediving in those days was self-taught, and considered somewhat of a pioneer. There were no courses or manuals, and everything they did and discovered was through trial and error. The secret to the talent of these daredevils also lay in their tenacity, (they always wanted to dive just a little further down), and in their belief that the impossible was just an attitude to be broken. Enzo Maiorca was a master of this particular ‘no such thing as can’t’ philosophy. In the 1960s, Professor Gabarrou, a physiologist for world renowned oceanographer Jacques-Yves Cousteau's team, had estimated that the maximum possible diving depth was 50 metres. Beyond this depth, he said that a person's rib cage would implode from external pressure.
Maiorca (who could often be heard saying “impossible is just an opinion”) wasn't convinced, and decided to test this 50 metre limit for himself. Maiorca plunged into apnea, and when he came back to the surface waving the 50 metre tag in his hand, he instantly shattered all possible assumptions about deep diving at that time. New dive limits were set, first at 75m, then at 101m, and then even deeper at 105m, but Mallorca and Mayol promptly defied them one by one. How did they do it? A few years later, it was discovered that the human body is able to perform what is known as thoracic haemo compensation, or ‘a blood shift’, which is when blood flow to the extremities is redistributed to the head and torso during a breath-hold dive, exactly as happens with dolphins, whales and other marine mammals. According to Boyle's law, at the same temperature, the pressure and volume of a gas are inversely proportional. At 50 metres there is a pressure of 6 atmospheres. This means that our lungs become six times smaller than normal, and, as a result, leave an empty space in the rib cage. Thanks to the blood shift, this space is gradually filled by the blood that our body automatically draws in from the surrounding areas to stop the rib cage from imploding. The human body, like that of large marine mammals, also implements another automatic adaptation mechanism when it is deep under water and cannot breathe: the heartbeat progressively slows down, and the oxygen present in the body is redistributed as slowly and as sparingly as possible.
