In case you missed it, Michael Phelps once again rallied to defeat his main rival in the 100-meter butterfly at the swimming world championships in Rome last week. After checking the scoreboard to make sure he had won, Phelps did something curious: He emphatically tugged at his swimsuit, the once vaunted Speedo LZR Racer, made in part of NASA-tested polyurethane panels designed to increase speed.

Why did Phelps do that? Because his rival, Milorad Cavic of Serbia, needled Phelps before the race about Phelps’ continued use of the Speedo model over a new all-polyurethane suit from a Speedo rival, Arena, that has proven to be even faster.