Freediving is a sport where divers hold their breath without breathing apparatus. It requires physical fitness, mental discipline, and training. The mammalian diving reflex helps divers hold their breath longer, but carbon dioxide accumulation is a limiting factor. Inexperienced divers should not hyperventilate before diving. Freediving can be dangerous, but with professional lessons, it can be a safe way to explore the underwater world.
Freediving, also called breath-hold or breath-hold diving, is diving without the benefit of a breathing apparatus. Freediving is a sport with different categories of competition such as diving with or without fins, weight sled, depth records set in the ocean, and freediving records set in pools. There are both men’s and women’s competitions in professional freediving.
Freediving requires extreme physical fitness, mental discipline and training. While human brain cells cannot tolerate freediving periods longer than five minutes and can become damaged after as little as three minutes, understanding the body’s reflexes, combined with training, allows world-class pros in freediving competitions to hold their breath up to nine minutes. This is mainly due to the exploitation of the mammalian diving reflex.
The mammalian diving reflex is a key factor in any freediving sport. When a person is immersed in water, certain processes naturally take over. Heart rate begins to slow down. With practice, it can beat up to four times a minute. Blood vessels constrict in the limbs, forcing blood into the body’s vital organs. At the same time, the blood vessels in the lungs fill with plasma, reducing their volume to prevent them from collapsing on themselves.
When the heart rate slows down, the body conserves energy. The air trapped in the lungs continues to oxygenate the blood. This extends the amount of time the body can safely go without breathing. However, since there is no respiration, carbon dioxide (CO2) builds up in the bloodstream and muscles. CO2 accumulation is a limiting factor in freediving. As the body becomes saturated with CO2, it activates an overwhelming reflex response to breathe.
Inexperienced freedivers sometimes hyperventilate before freediving, believing that this saturates the blood with oxygen, allowing for a longer dive. It doesn’t actually increase oxygen, but removes CO2 from the blood, simply delaying the reflexive need to breathe. This is extremely dangerous and even life-threatening, as the body can run out of oxygen before the diver feels the need to take a breath. When this happens, the diver can pass out underwater. Shallow water blackout is believed to be responsible for many drowning accidents.
Freediving is an exhilarating but potentially dangerous sport that can result in serious injury or death. Pressures on the body in deep water freediving can reach 235 pounds per square inch (16.5 kilograms per square centimeter). While freediving has roots dating back over 4,000 years, when people often dived for pearls and food, today’s enthusiasts are encouraged to take professional lessons to learn how to safely enjoy this extreme sport. For those who go safety first, freediving can be a nice way to experience the ever-exotic underwater world.