A taxi ran over Guglielmetti when he was a child, but he escaped unharmed. He later fell from a four-story building, but managed to cling on power cables and survived. Originally a pole vaulter, he joined a gymnastics club in 1927, where he was coached by Mario Corrias. Three years later he became a member of the national team. Although he won two Olympic gold medals in 1932, he faced a strong competition in Italy, and won his first national all-around title only in 1934. He defended it in 1935, 1937, 1938 and 1939.