No athletic event has benefited from advances in technology quite like the Olympic Games. Fencers use state-of-the-art sensors to make sure their attacks are properly recorded; underwater robot cameras capture swimming relay and diving highlights.

But gymnasts and runners still sport some surprisingly low-tech assistance: they get a number on a piece of paper that's held in place with safety pins. What gives?

Technically, athletes wear what’s called a bib—a sheet of thin plastic known as Tyvek that withstands sweat and moisture and is able to move with the wearer’s body. According to Tyvek retailer Running Count, the product is also tear-proof, though whether they mean rips or actual salty discharge from a losing effort—or both—is uncertain.

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Originally, the numbers printed on the bibs were used to identify entrants for judges, who are often tasked with keeping track of multiple competitors. But with the advent of computer chips and timers, it’s become less crucial to slap a number on an athlete. According to WIRED, the bibs are now in place simply because it’s a prime spot for sponsor logos, who pay millions to be featured on the international telecasts. (This year, Nike updated the bibs so they can be affixed using 3D printed plastic “teeth” that stick to clothing. Although the idea wasn’t quite ready in time for the Rio Games, at least there’s progress.)

While athletes don’t get to choose their number, they can still find significance in it. When 1976 gold medal winner Nadia Comaneci donated her bib to the Olympic Museum in Lausanne, Switzerland in 2014, she noted that “73” reminded her of the number of perfect 10 scores she received (seven) and the number of gold medals earned (three). Here's hoping the museum isn't using safety pins to display it.

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