I have a little quirk when I watch movies: whenever a diving scene comes up, I deliberately hold my breath along with the character, just to see whether I can last as long as they do.
Of course, I have never won—not even come remotely close. The protagonist has barely gone underwater before I am hit by a powerful urge to breathe, as if my life depends on it. I used to chalk up my failures to two things: 1. my cardio-respiratory fitness is terrible—I have dreaded long-distance running ever since I was a kid; 2. movies must be exaggerating.
But I only recently realized I had missed the most important factor: comparing my breath-holding performance on a sofa with a movie character’s underwater performance is simply unfair. Your ability to hold your breath is completely different on land and in water.
Humans are exceptionally good at holding their breath in water.
Once a person is immersed in water, their body undergoes a series of physiological responses now known as the “mammalian dive reflex.” These physiological responses include:
1. A sharp drop in heart rate
Even while exercising vigorously underwater, your heart rate drops, helping your body conserve oxygen for as long as possible. STéphane Mifsud, the world-record holder for static apnea underwater, can lower his heart rate to an astonishing 20 beats per minute.
2. Peripheral vasoconstriction
The blood vessels in your arms and legs nearly close, sending blood toward the core of your torso and allowing oxygen levels in your heart and brain to be maintained for as long as possible. This redistribution of blood toward the torso also helps the lungs withstand the pressure of deep diving, because blood, unlike air, is almost incompressible.
3. Spleen vent
The spleen mainly acts as a blood filter, but it also contains a large supply of oxygen-rich red blood cells that can be used in an emergency. During a dive, the spleen contracts, pushing oxygen-rich red blood cells into the circulatory system like a sponge being squeezed dry. This is called a spleen vent.
You do not need to immerse your whole body to trigger these changes; simply immersing your face in cool water can induce the mammalian dive reflex. When people feel agitated, splashing some cold water on their face can calm them down—the mechanism may be that it induces the mammalian dive reflex.
In fact, experienced divers do not even need to touch the water. As they prepare to dive, their heart rate has already begun to fall—another example of the brain integrating various kinds of information to regulate physiological responses.
At present, the world-record holder for static apnea (holding one’s breath while floating face-down in a swimming pool) is a Frenchman named STéphane Mifsud, whom I mentioned above.
In 2009, he held his breath continuously in a swimming pool for 11 minutes and 35 seconds, setting a world record. As for the 17 minutes and 04 seconds the American magician David Blaine once spent holding his breath underwater on a television program, I do not believe he did it purely on the strength of his own abilities.
References:
Hutchinson, A. (2018). Endure: Mind, body and the curiously elastic limits of human performance.
Note
- This article series, “New Findings in Psychology: A Short Course,” was written at the time as popular-science commentary related to Zhichao Wei: New Findings in Psychology. It was published on the now-closed platform Fantuan, and the original link no longer exists.
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