He led the strike and the emerging trade union structures in the "Toral" factory in Toruń. Later on he was elected to a member of Toruń's Solidarity union management. During the martial law Musielak was arrested and he spent a year in prisons in Potulice and Strzebielinek.[2]
After leaving jail in December 1982, he continued his activities for the Polish anti-communist opposition. As one of his tasks, he was responsible for a periodic magazine TIS, printed illegally by the union in Toruń.[citation needed]
After the breakthrough in 1989 he was elected a president of Solidarity District Toruń, leading the organization for 2 years (1989–1991).