If you've been following the swimming competitions in Rio, then you've probably noticed athletes such as Michael Phelps and Katie Ledecky peel off their cap only to reveal a second cap underneath, after they've completed their race.
No, this isn't a Matryoshka doll situation.
According to Yahoo! Sports, swimmers wear two caps for two reasons: The first being that two caps help secure the swimmer's goggles, which sit in between the first-layer cap, made of latex, and the top-layer cap, made of silicone.
Katie Ledecky of the United States peels off her cap at the Women's 200m Freestyle Final on Day 4 of the Rio 2016 Olympic Games on August 9, 2016 in Rio de Janeiro, Brazil. (Photo by Adam Pretty/Getty Images)
The second reason is one of the most important, according to The Washington Post. The two caps create a "slight performance-enhancing effect." Adding a second silicone cap can shave off those precious milliseconds.
"The outer silicone cap better maintains the shape and does not wrinkle as much [as the inner latex cap], thereby causing less drag," former women’s Olympic assistant coach Dave Salo told Yahoo! Sports during the 2012 London Olympic Games. Thus, a smooth cap can make all the difference between reaching the podium and not.
Latex caps also stick to the head better than the silicone ones, which can slip off, as U.S. swimmer Dana Vollmer found out during the 100-metre butterfly final at the London Games. However, that didn't stop her from winning gold, which just shows that caps can only help you so much.
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