What does band A of the sarcomere contain?

Band A of the sarcomere contains the thick filaments, primarily made up of myosin, and overlaps with the thin filaments, primarily composed of actin. This band appears dark under a microscope due to the dense packing of these filaments. The A band remains constant in length during muscle contraction, while the I band and H zone change size. Additionally, the A band includes the entire length of the myosin filaments, regardless of their overlap with actin.