Sir won three gold medals at the 1935 International University Games in Budapest, running 10.8 and 21.6 for 100 and 200 metres and 41.6 with the Hungarian relay team. At the 1936 Summer Olympics he advanced to the semi-finals in the 100 metres; he placed last in his semi-final and was eliminated. In the 200 metres he went out in the quarterfinals, and the Hungarian relay team failed to qualify for the final.