During swimming competitions you often see athletes take off their caps and discover a second one underneath. In a sport where victory is played out on hundredths of a second, every tiny advantage counts. There double headphones serves to guarantee maximum hydrodynamics possible, eliminating folds that would create resistance, and a secure the goggles securelypreventing its movement in critical phases such as the starting dive or turns. It is no coincidence that this solution has been adopted over the years by champions such as Michael Phelps or Federica Pellegrini, who took care of every single technical detail. This seemingly banal choice therefore hides a scientific calculation to maximize performance and reduce any potential hitch.
Double cap and hold of swimmers’ goggles: stability during dives and turns
The first reason swimmers wear two caps is holding the goggles. During the dive the impact with the water is very strong and can move the elastics, causing water infiltration or the loss of the goggles themselves. For a professional swimmer, even a slight movement of the goggles at the start of the race is an unexpected event that can compromise the entire performance.
To avoid this, many athletes wear a very tight first cap, place the elastics of the goggles over it, and then apply a second cap that blocks the elastics and prevents unwanted movements. The double layer therefore increases the overall seal and guarantees stability in the race.
Like silicone, it reduces creases created by latex
The double cap is chosen to reduce water resistance and optimize movement efficiency. The surface of the swimmer’s head must be as uniform and smooth as possible: even small creases can generate turbulence and slow down progress, increasing resistance.
There first headsetusually in latexit is very thin and adherent, and does the job of keeping hair and glasses in place. However it tends to form small ripples. There second headphonein siliconeis thicker and more rigid, and serves to cover these irregularities, creating a smoother and more hydrodynamic surface. By also covering the elastic strap of the goggles—made of rougher materials that increase friction with the water—the outer cap further helps maintain a more uniform profile, eliminating an additional potential source of resistance.
Hydrodynamic studies show that a perfectly smooth surface can reduce drag in the water (passive drag) of approximately 5%highlighting how even small irregularities can affect the efficiency of movement.
Furthermore, the second headphone also performs a crucial function reserve in case the cap should come off completely. The usefulness of this “safety margin” was highlighted at Paris Olympics 2024, where the loss of headphones of the American Emma Weber requested the interruption of the race due to her removal from the bottom of the pool.
In a race where the blink of an eye can mean the difference between gold and silver, the combination of these small measures translates into a competitive advantage. It is proof that, in swimming, attention to technical details is as important as training in the pool.
