Henych, who started for the Spartak Vrchlabí and the Dukla Liberec , made his first international appearance at the 1972 Winter Olympics in Sapporo . There he finished 21st place over 15 km, ninth place over 30 km and eighth place with the relay. In the 1973/74 season he achieved tenth place over 15 km and eighth place over 50 km at the Lahti Ski Games and won the silver medal over 50 km behind Gerhard Grimmer at the season highlight, the 1974 Nordic World Ski Championships in Falun . In addition, he finished there in 13th place over 15 km and fifth place with the relay and reached fourth place in the unofficial overall World Cup at the end of the season. At the Olympic Winter Games in Innsbruck in February 1976 , he ran to 46th place over 15 km, 30th place over 30 km and tenth place with the relay. In December 1976 he took second place over 15 km in Davos . He completed his last international races in the 1977/78 season. He was third with the relay at the Svenska Skidspelen . At the Nordic World Ski Championships in Lahti in 1978 , he came in 44th place over 30 km and 36th place over 50 km.
In the Czechoslovak championships, Henych won four times over 15 km (1971, 1973, 1974 and 1976), twice over 30 km (1974, 1976) and five times with the relay (1971, 1972, 1975, 1976, 1979) of Dukla Liberec. In 1975 and 1979 he was second over 15 km, 1977 and 1978 second with the relay, 1978 second over 50 km and 1975 third over 30 km.