Stem cells located between the endomysium and sarcolemma that function in the repair of damaged muscle tissue are called

Stem cells located between the endomysium and sarcolemma that function in the repair of damaged muscle tissue are called myosatellite cells.

Those cells are called stem cells because of their multipotency (differentiate into several cell types). Myosatellite cells are able to give rise to more satellite cells or to differentiate into skeletal muscle cells.