Stasys Šaparnis started his sporting career as a swimmer and water polo player, winning his first championship medal, a silver, at the Lithuanian SSR championships in water polo in 1960. Soon after that he switched to modern pentathlon and won Lithuanian SSR modern pentathlon titles in 1961-63, and 1971-72. Besides his Olympic silver medal, Šaparnis won a team title in 1969, three silvers (1967 in individual and 1966 and 1970 in team event) and one bronze (1967 in team event) at the World Championships. At the Soviet championships, he was not as successful, winning only one individual medal, a silver in 1970. But at the team event, Šaparnis was a Soviet champion in 1965, took silvers in 1963 and 1972 and bronze in 1968. After finishing his sporting career, he worked as a coach for a short while, before becoming a modern pentathlon judge and sports official. From 1988-92, Šaparnis was president of the Lithuanian Modern Pentathlon Federation and from 1992-96 he was vice-president of the Lithuanian Olympic Committee.