Freediving Research Examines Human Breath-Hold Limits and Health Effects

Physiologists are examining competitive freedivers to measure how the body responds to prolonged breath-holding and deep underwater pressure. The research tracks changes in oxygen levels, heart rate, lung volume, and carbon dioxide buildup during dives.

At 70 meters, water pressure compresses lungs to roughly the size of a soda bottle, and blood shifts into the chest cavity. Some divers reach depths of 136 meters with fins or swim 326.5 meters underwater in a pool, according to records cited in the coverage.

Shallow water blackout occurs when the brain loses oxygen without prior warning signs. Investigators determined that Tucker Francis, 19, died from this condition during a recreational freedive in the U.S. Virgin Islands in 2017. Britt Jackson, executive director of Underwater Hypoxic Blackout Prevention, documented 110 blackout deaths over the past two decades through online reports and drowning records.

Males ages 15 to 45 appear most affected, based on the available data.

University has monitored oxygen consumption, heart rate, and lung function in competitive athletes. The measurements may help develop warning devices for swimmers and improve understanding of lung and heart function in the broader population. Indigenous groups in Japan, Korea, the Philippines, and Indonesia have practiced freediving for foraging for thousands of years.

Modern competitions began in the 1970s, and an estimated 4 million people now participate worldwide.