What repeating units make up a muscle fiber?

A muscle fiber is made up of repeating units called sarcomeres. Sarcomeres are the basic units of muscle contraction. Each sarcomere is composed of two thick filaments (myosin) and multiple thin filaments (actin). The thick and thin filaments are arranged in a repeating pattern, with the thick filaments in the center of the sarcomere and the thin filaments surrounding them. The sarcomeres are connected to each other by a protein called titin, which helps to maintain the structure of the muscle fiber.