Watch This Freediver's Heart Rate Drop to 37bpm

To conserve oxygen, freedivers intentionally let their heart rates drop below 40bpm in the water.
Stig Pryds at the bottom of deep pool Nemo
Counting bottom time © Daan Veerhoeven
By Josh Sampiero

It's not a stretch to think that freediving is one of the craziest (and riskiest) sports there is. But the training and approach the divers undertake makes it seem a little less crazy.

Descending to depths of up to 330 feet beneath the surface of the ocean, these calm, collected athletes experience things most of us never will, including having their heart rates drop to a mere 37 beats per minute.

A normal human's resting heart rate? Usually closer to 65bpm. Watch the video below to see how slow it can go for diver Stig Pryds.

What’s happening here is known as the dive reflex — the body’s automatic, subconscious reaction to going deep underwater. What else happens? Blood shifts from your arms and legs to your core, the brain itself slows down and — get this — your lungs shrink to the size of an orange! You can learn more about the anatomy of a freedive here.

Stig Pryds at the bottom of deep pool Nemo
Focusing on staying calm © Daan Veerhoeven

So what’s happening in this video? This is a controlled, careful dive in one of the world’s deepest pools, known as Nemo 33, in Brussels, Belgium. There, divers can descend 113 feet underwater in the 660,000-gallon pool.

At the beginning of the video, Pryds’s heart rate actually goes up as he sucks in the oxygen needed to sustain his dive. Then his heart rate slowly lowers as he descends to the bottom, eventually dropping to 37bpm. Interestingly, his heart rate only increases slowly as he returns to the surface, then jumps rapidly when he takes his first breath.

That’s because the dive reflex is all about conserving oxygen, obviously a good thing when you’re underwater. The most interesting thing is that while the reflex is subconscious, it can be trained. Professional freedivers like Pryds can amplify the effects, extending their time underwater even further.

read more about
Next Story