"If Team USA was as fearful as Trump, Michael Phelps and Simone Biles would be cowering in the locker room, afraid to come out and compete," the Democratic nominee said. 
"America isn’t afraid to compete," Clinton added.
Clinton's Olympic reference came during a riff against Trump, who has broken from GOP orthodoxy and vocally criticized international trade deals.
"Mr. Trump may talk a big game on trade, but his approach is based on fear, not strength," Clinton said in her speech on the economy in Warren, Mich. "Fear that we can't compete with the rest of the world, even when the rules are fair. Fear that our country has no choice but to hide behind walls." 
Phelps is going for his 22nd gold medal on Thursday night when he enters the pool for the 200-meter individual medley, while Biles is competing for all-around gold Thursday in women's gymnastics. 
Clinton has tried to use the Olympics as an opportunity to gain supporters. She is airing more than $13 million in campaign ads during the summer games in Brazil.