The H zone of the sarcomere is composed of?

The H zone of the sarcomere is composed of thick filaments, and is the region at the center of the A band. It appears lighter in color because it is the region where thin filaments do not reach. In relaxed muscle, the H zone is visible as a lighter region in the middle of the A band, but it disappears during muscle contraction as the thin filaments slide inward among the thick filaments.