The science of holding your breath

Feb 21, 2002, vol.23, no.4
By Marianne Meadahl

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When Alan Morgan stops breathing, researchers in SFU's environmental physiology lab start measuring the changes that take place in his body before he draws his next breath of air - two long minutes later.

The measurements show how the body responds when air intake is limited and are beginning to explain how the body controls its cardiorespiratory functions (including heart, blood vessels, lungs) under such conditions.

Morgan is one of 20 students learning to become freedivers - those who can descend to great depths under water on a single breath - as participants in SFU's freediving clinic.

The three-month course runs until April at the SFU pool, where students, who have little or no experience in the sport, are learning various techniques practiced by elite freedivers, who can plunge to 60 meters and beyond on a single breath.

By the end of the course, many students will be able to increase their breath holds from two minutes to an amazing four or five minutes. To achieve that, students are learning about such techniques as air packing, which involves pushing air deep into all available air spaces in the lungs. Other techniques, such as meditation, hypnosis and visualization are also used in an attempt to slow their heart rates.

While students learn a new skill, kinesiologists Andrew Blaber and Erik Seedhouse are using the opportunity to learn more about what happens to the divers' bodies while they hold their breath and as they develop the ability to extend them. Blaber, director of the school of kinesiology's environmental phy-siology lab says initial testing of the students is shedding light on a little understood phenomena and will help those who train freedivers to improve their training techniques.

Preliminary testing hopes to determine how the freedivers increase their lung volumes, which elite freedivers attain through stretching exercises and breath-hold practice, as well as whether or not here are changes in the autonomic control of the heart and the vascular system. Researchers are recording measurements of how the cardiovascular system functions and how the body regulates its use of oxygen during breath holds.

Measurements of students at the start and end of the course will be compared to see how cardiovascular control changes after training. Further comparisons will be made with results of similar tests on elite freedivers, including several world record holders from the Vancouver area, and with a group of volunteers not involved in the sport.

“We're using that period of time when no new oxygen is being brought into the body to look at how the functions of the cardiovascular system change with respect to how it operates during normal breathing,” says kinesiology graduate student Val Walker. “As the duration of the breath hold increases, up to four, five, or even six minutes, we get a chance to see how the body adapts over a longer period than has so far been studied.”

Some initial data was collected during the first clinic last spring, but researchers have since refined their focus. Walker has designed a breath-hold mask, made from a standard firefighter's safety mask, that allows researchers to regulate conditions during the breath hold and measure changes in gas concentrations while the subject is seated in the lab.

The mask can also be filled with water to recreate a diving environment. Researchers expect to test about 30 subjects by mid-spring.

The freediving course is led by Kirk Krack, coach of many world-record holders and the Canadian freediving team, which placed second in world competition last year.

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