See this guy’s heart rate go to 37bpm

Did you know freedivers intentionally let their heart rates drop to under 40bpm? Watch it happen.
By Josh Sampiero

We all agree that freediving is one of the craziest (and riskiest) sports there is.

Descending to depths of up to 100m beneath the surface of the ocean these calm, collected athletes experience things most of us never will – including their heart rates dropping to a mere 37 beats per minute.

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

Checking the rate

Stig Pryds at the bottom of deep pool Nemo
Counting bottom time © Daan Veerhoeven

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.

Staying calm

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, in Brussels, Belgium. There, divers can descend 34.5m underwater in the 2.5 million-litre pool.

At the beginning of the video, diver Stig 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 Styg can amplify the effects, extending their time underwater even further.

Like this stuff? Check out more incredible adventures, like Double Space Net in Moab!

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