Myrvoll graduated from secondary school in 1968. He had various jobs in the construction industry until 1972, when he became a student. From 1975 he worked as a slaughter until 1978, when he started working at Norsk Jernverk. He was a full-time trade unionist from 1983 to 1988. In 1989, he was elected to the Parliament of Norway representing Nordland. He was re-elected on two occasions. While in parliament, he sat on the Standing Committee on Transport and Communications. From 2001 to 2005, he sat as a deputy member. Myrvoll was mayor of Rana from 2003 to 2007, and has been deputy mayor since 2009.
