A member of the Cuban national basketball team, Juantorena switched to track at age 20. Standing 1.88 metres (6 feet 2 inches) tall with a powerful 2.75-metre (9-foot) stride, Juantorena became known as “El Caballo” (“The Horse”). A year after his first 400-metre race, he competed in the 1972 Olympics in Munich, West Germany, where he was eliminated in the semifinals. He then won all of his 400-metre races in both 1973 and 1974 before having two operations on his foot in 1975.

By 1976 Juantorena was healthy enough to run not only the 400 metres in Montreal but also the 800 metres, a distance he had begun running to build endurance following his injury. An unknown internationally at that distance, Juantorena not only won Cuba's first track gold medal but also set the world record (1 min 43.5 sec). By the finals of the 400 metres, Juantorena was running his seventh race (of nine) of the Olympics, yet he still ran the fastest 400 metres of his career (44.26 sec) to win his second gold medal. Juantorena concluded his Olympic career in 1980 at Moscow with a fourth-place finish in the 400 metres. He retired from competitive racing in the mid-1980s to become an international sports administrator.