Martyn played his early football in Tasmania and in 1976, his debut season, he was named as the TANFL's 'Rookie of the Year'.
He was a member of the strong Sandy Bay team of the late 1970s and played in three consecutive premierships from 1976 to 1978.
Martyn appeared in 32 senior games for Melbourne before crossing to Port Adelaide during the 1981 season.
Martyn was a Tasmania interstate representative and won the Lefroy Medal as the state's best performed player in 1982.
His career ended in disappointment with a loss in the 1986 Grand Final to Glenorchy and he finished with 129 senior games.