In his teens, Dora began competing successfully as a girl at sports, apparently being "too embarrassed to talk about what was happening to him". In 1936, he took part in the Olympics, his teammate Gretel Bergmann stating: "I never had any suspicions, not even once... In the communal shower we wondered why she never showed herself naked. It was grotesque that someone could still be that shy at the age of 17. We just thought, 'She's strange. She's odd'... But no-one knew or noticed anything about her different sexuality." In 1938, Ratjen competed at the European Athletics Championships, and won the gold medal with a world record jump of .