During his active career he won two individual FIS Nordic World Ski Championships medals (1954: silver, 1958: bronze) and the Holmenkollen ski festival three times (1952, 1959 (shared with Sverre Stenersen, and 1960). He finished eleventh in the Nordic combined event at the 1960 Winter Olympics in Squaw Valley.
His most significant impact on Nordic combined was creating the "Gundersen method", in use since 1985. This method recalculated the ski jumping points into cross country skiing start times with the athletes then starting at staggered times with the winning ski jumper starting first. For the 15 km individual and the 7.5 km sprint, the difference between the competitors at the start of the cross country portion of the event was one ski jumping point equaling four seconds. For the 4 × 5 km team event, one ski jumping point equaled 3 seconds, but this was changed in 1995 to one point equaling 1.5 seconds, then in 2005 to one point equaling one second, and then again in 2009 to one point equaling 1.33 seconds.