Olympics: Why swimmers wear two caps in the pool

Dana Vollmer won gold in the 100m butterfly at London 2012 despite one cap coming off

In a sport where Olympic glory can be decided by a fraction of a second or fingertip, swimmers look for any advantage to cut through the water as efficiently as possible.

And this includes wearing a swim cap. But not just one swim cap.

For most competitors will dive into the pool at the Tokyo Aquatic Centre this week wearing two.

Experts say that there are two reasons for wearing one swim cap on top of another, apart from keeping longer hair out of the swimmer’s face.

The theory behind two caps is that that it helps stabilise the swimmer’s goggles, and by covering up the exposed straps of the goggles, reduces drag in the water.

That reduction in drag allows the swimmer to move through the water with increased efficiency, at a higher speed and finish the race in a faster time.

In most cases the swimmer’s goggles sit on top of a first cap made of latex, which is then covered by a silicone swim cap.

Observers say that friction of the silicone cap against the latex cap prevents the top one from coming off, while latex is more likely to wrinkle and tear.

Dave Salo, an assistant coach for the 2012 US Olympic Women’s Team, says that the latex caps tend to wrinkle more than the silicone ones.

“The outer silicone cap better maintains the shape and does not wrinkle as much, thereby causing less drag,” he previously told Yahoo!

It is rare for any of the caps to fall off.

But at the 2012 London games, Dana Vollmer won gold in the 100m butterfly despite one of hers coming off.

“The top cap came off,” Vollmer said after the event.

“I have never had that happen before. I thought about it, and maybe it kept my mind off my legs hurting or something. I don’t know.”