Why is hyperventilation before underwater swimming considered dangerous?

Hyperventilation before underwater swimming is considered dangerous because it can lead to sudden loss of consciousness and, in some cases, death. When a person hyperventilates, they exhale excessive amounts of carbon dioxide (CO2), which can lead to a temporarily lowered level of CO2 in the blood. This condition, known as respiratory alkalosis, can cause a range of physiological responses, including lightheadedness and disorientation.

While swimming underwater, the risks associated with hyperventilation are particularly concerning. The body's drive to breathe is primarily stimulated by CO2 levels rather than a lack of oxygen. After hyperventilating, an individual may feel a false sense of security and may not recognize their need to breathe until it is too late. This delayed response increases the risk of blacking out underwater, which can be fatal if the swimmer is unable to resurface for air. The lack of awareness regarding their deteriorating condition, combined with the underwater environment, greatly heightens the risk of drowning.

Understanding this risk is crucial for swimmers and coaches, as it highlights the importance of safe breathing practices before and during underwater activities.