The primary reason for exhaling before you surface dive in a lake or pool is so that you can stay submerged for a longer period. There are important physiological processes in the body that allow this technique to work. It is important to note that surface diving is extremely dangerous and that you should be supervised at all times by a trained professional when performing this technique.
Concentration of Carbon Dioxide
The concentration of carbon dioxide in the blood is one of the key regulators of breathing. The body stores carbon dioxide in the blood as bicarbonate. The act of exhaling, and exhaling frequently, prior to a dive stimulates the release of carbon dioxide from the blood through the lungs, which reduces the levels of bicarbonate in the blood. Chemical receptors in the blood vessels read the concentration levels of bicarbonate and carbon dioxide in the blood and the resulting pH levels of the blood as well. Changes in these levels dictate how quickly the body must breathe to maintain balance.
Urge to Breathe
The resulting alterations in blood pH and concentration of carbon dioxide that result from exhaling before a dive decrease the nervous system's urge for another breath. The body is more regulated by the need to expel carbon dioxide than intake oxygen in normal circumstances; however, this technique bypasses the need to expel the carbon dioxide, which then allows oxygen depletion to dictate the need to breathe.
Dive Time
Performing the exhale before surface diving will indeed increase the length of time you are able to stay submerged in water without the need for breathing. The typical urge for breathing in normal conditions without the exhale is around 15 seconds, according to Ernest Campbell's article "Free Diving and Shallow Water Blackout." The exhale technique will allow you to practice longer breath holds, which will in turn train the body to stay underwater longer without the need for a breath.
Precautions
As stated previously, surface diving and the exhale technique always should be practiced under close supervision. Excess hyperventilation as a result of frequent exhaling can cause a blackout when underwater, as well as an overzealous euphoria that might increase confidence in breath holding technique beyond your current levels. These two potential outcomes can lead to drowning and depth. It cannot be stressed enough that these are advanced techniques that require years of practice and supervision for effective surface diving performance.
Member Comments