Hold It!

Probably an endangered hawksbill sea turtle, 2007 

Marine mammals and reptiles (and even some birds like shearwaters) have to hold their breath if they want to dive down for food in the ocean environment.  Its rather amazing how long some of them can go without fresh air.  Bottlenose dolphins can go about ten minutes, walruses can manage twenty, harbor seals can eek out thirty minutes on a good day.  Of course the marine reptiles blow them right out of the water since sea turtles can hold their breath upwards of five hours.

Yes, five hours.  In fact there is a species (maybe a subspecies) of turtle in the Pacific – the black sea turtle – that is known to hibernate for five months at the bottom of the ocean.  So you could argue that they can hold their breath for 3600 hours!

Still, all of the marine mammals beat the average human.  On average, people manage to hold their breath forty seconds to one minute.  (Even polar bears beat that by holding their breath for two!)  The truly interesting thing, to me, is the behavior that people exhibit while holding their breath.  Its interesting, because as far as I know, these behaviors don’t necessarily help you hold your breath longer. 

Many people pinch their nose and swallow so much air that their cheeks balloon up.  Others will forego the cheeks but keep the pinched nose.  Practically no one continues to go about their normal buisness and very very few people fidget. 

Why does that seem significant to me?  Well.. marine mammals don’t just hold their breath and space out!  They have lives to run and fish to catch beneath the waves.  Their breath holding periods are active, and they still manage to keep things under control for incredibly long periods compared to us. 

[PS: The trick to holding your breath longer than a minute – my best time is 1’45” – is to slightly hyperventilate by taking three huge breaths quickly and then holding the fourth breath and starting the clock.  It seems to push out the old air.  Free divers do it.  Most marine mammals naturally do this, they exchange out huge volumes of air with each breath and are in essence always breathing deeply.  Humans exchange a paltry 17% of lung volume on an average breath while bottlenose dolphins exchange 80%!]

Come to think of it I have a question about oxygen consumption in people!  I’m a runner and we sometimes talk about VO2 max when training.  Basically its how much oxygen your body can consume and efficiently process, its also a measure of how fit an athlete is.  But what I’m curious to know: can athletes hold their breath longer than the average population or does their increased muscle mass impose higher oxygen demands on the system and lower their breath holding ability?  Hmmm.  Any exercise physiologists out there care to set me straight? 

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