The aim of the present work was to investigate the features of satellite cells and other adult stem cells in skeletal muscle. Satellite cells are located between the basal membrane and the sarcolemma of each muscle fiber. First, we developed a mode! based on muscle satellite cell c ulture to investigate the regulation of adult Myosin Heavy Chain (MyHC) isoform expression in pig muscle. Satellite cells were harvested from the mostly fast-twitch glycolytic longissimus (LM) muscle collected at the fast rib leve!, and the predominantly slow-twitch oxidative rhomboideus (RM) muscle of 6-week-old piglets. Then, we investigated more extensively the features of ali adult stem cells in both muscles of growing and adult pigs using flow cytometry. The first study demonstrated that satellite cells from LM and RM only expressed the embryonic and fetal MyHC isoforms in ce li culture, without any of the adult MyHC isoforms expressed in vivo. The second study clearly indicated that adult stem cells from pig skeletal muscles expressed a panel of stem ce li markers exhibiting age-related changes.