This Olympic swimmer made a joke, and the Russians took him seriously
The U.S. and the former Soviet Union competed over everything in the years of the Cold War. The Olympic games were one of their favorite arenas in which to face off. American and Soviet athletes went to great lengths to beat each other, which is why they were always searching for strategies to improve their performance.
When nine-time gold medal winner Mark Spitz joked that his mustache was the secret to his success, the Russians believed him. Well, there is no official confirmation that he was taken seriously, but given that every Soviet swimmer grew one out the following year, they likely did.