In the eight years since its addition to the Merriam-Webster dictionary, athleisure, a label for luxurious sportswear more suited for lounging than working out, has become a pervasive fashion trend.

And Swiss watchmakers have put their own spin on it by adding rubber straps to timepieces set with diamonds or other precious gems. Consider the Hermès Cut, introduced at the 2024 Watches and Wonders Geneva fair, with rubber straps in colors such as green, lavender and the distinctive Hermès orange. And Breguet’s new addition to the Marine collection, the diamond-set Marine Chronographe 5529, available with a midnight-blue rubber strap.

“The pairing of rubber and diamonds on a watch reminds me of Marc Jacobs’ spring-summer 2008 collection for Louis Vuitton,” Scarlett Baker, a stylist and watch writer in London, wrote in an email, referring to the collection’s handbags created in a mix of suede, fabric, satin and acrylic appliqués in bold, contrasting colors. “It’s playful, it’s provocative.”

For some makers, the unusual combination has become a defining feature. The Swiss brand Gerald Charles, for instance, said it began offering rubber straps with gem-studded watches about two years ago. While it would not disclose details, it said the combination now produced 10 percent of its total sales.

“It’s very much in line with the sporty yet elegant aesthetic that Gerald Charles envisioned for the brand and that we are still pursuing,” said Federico Ziviani, the chief executive of the brand founded in 2000 by the celebrated watch designer Gerald Genta. “Diamonds are typically associated with evening wear, but at Gerald Charles, we wanted to break conventions.”