Filed under: Swimming
Swimmers and free divers who hyperventilate before holding their breath for long periods underwater are at risk of hypoxic blackout—loss of consciousness—that can result in brain damage and death. (It sometimes is known as “shallow water blackout,” but this can be confusing because there are other causes of “shallow water blackout.”)
Hypoxic blackout often affects skilled, fit, and competitive swimmers and free divers. They practice breath holding or hypoxic training in water to increase their ability to hold their breath for longer periods of time. But depending on the technique, this can be a dangerous practice.
Breathing is a process of exhaling carbon dioxide (CO2) and inhaling oxygen. The actual urge to breathe is caused by a buildup of CO2 within your lungs. If you simply try to hold your breath underwater, the physiological urge to breathe will eventually take over so there isn’t a significant risk of “passing out.” However, some swimmers and free divers have found that if they hyperventilate before diving into the water —either by rapid breathing or taking deeper breaths—they can hold their breath for longer periods of time. It’s the act of hyperventilating that can be deadly.
When you hyperventilate before underwater swimming, the amount of CO2 is reduced in your lungs and the urge to breathe is diminished. Without warning, you can lose consciousness—at which point a breath is forced and water fills your lungs. Unless rescue is immediate, brain damage and death are likely outcomes.
Training with instructors and a skilled free-dive or swimming community will help reduce your risk of tragic accidents. In addition, there are other things you can do to avoid hypoxic blackouts.
- Don’t hyperventilate before underwater swimming.
- Never swim alone.
- Don’t ignore the urge to breathe underwater.
Water/pool workouts and swimming are great ways to give aching joints a break or recover from an injury and still get in a good workout. Exercising in the water provides the same aerobic fitness benefits as exercising on land. In fact, exercising in water may be less work for your heart; it pumps out more blood per beat, and heart rates are slightly slower. What’s more, pressure from the water speeds blood flow back to your heart, where your blood gets the oxygen that your muscles need during exercise.
Aquatic exercise is great for most people, including older and younger folks. Consider jumping in a pool to reduce stress and the risk for overuse injuries and as an alternative to your usual exercise routine.