Michael Phelps did it. The Russian women's saber fences did it. So did Usain Bolt. Simone Biles -- heck, the entire "Final Five" -- did it. If you've watched any of the medal ceremonies at the Olympics, you've no doubt seen it: winning athletes biting their medals.

It doesn't matter the sport, or the medal -- gold, silver or bronze -- it seems like all athletes get a sudden urge to chow down on their prize moments after they receive it.

Take a look:

WATCH: Why athletes bite their medals

Is it because they're so hungry after exerting all they have in their respective sport? Is it to test the medals to see if they're real? Is it because that's just what they've seen other athletes do over the years?

The answer appears to be much simpler: they're just doing what they're told.

David Wallechinsky, president of the International Society of Olympic Historians and author of The Complete Book of the Olympics, told NBC News back in 2012 that photographers ask athletes to take a bite of their medals.

"There are groups of photographers, they're always like, 'Natalie, Natalie, Natalie -- do it, do it,'" said Olympic medalist Natalie Coughlin. "[They're yelling] 'hold up your medal, hold it to your face. Bite it. bite it. Bite it'...They wear you down and make you bite it."

It's not known when the trend began, but historians believe that athletes may have munched on their medals to test the metal. While biting into gold can leave an indentation, modern Olympic medals aren't made of pure gold.

It hasn't always ended well. Back in 2010, luger David Moeller reportedly broke a front tooth biting into his silver Olympic medal, NBC News reported.

Speaking of medals, did you know that winners have to pay taxes on them? Click here for more.

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