The second reason, however, might be the most important. Two caps, including an inner latex cap and an outer silicone one, have a slight performance-enhancing effect.
“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 Games in London.
This, of course, raises the question: Why don’t swimmers just wear silicone caps if the latex ones wrinkle?
Latex caps stick to the head better, while the silicone variety can slip off, as it did off the head of U.S. swimmer Dana Vollmer during the 100-meter butterfly final at the London Games.
Considering Vollmer still won the gold — even with just the one cap — it’s clear that the performance-enhancing effects of two caps only go so far.
More on Olympic swimming: