Final answer:
The true statement highlights the role of myosin cross-bridges in muscle contraction, where myosin pulls on actin, shortening the sarcomere and creating force through cross-bridge cycling, as explained by the sliding filament theory.
Step-by-step explanation:
The statement is true: Myosin cross-bridges do indeed pull on actin, shortening the sarcomere and creating a concentric force. This process is at the heart of the sliding filament theory, which explains muscle contraction. During this process, myosin heads attach to binding sites on the actin filaments; the heads then pivot, pulling the actin filaments closer together within the sarcomere. This action shortens the sarcomere, the basic unit of striated muscle fibers, leading to muscle fiber contraction.
Cross-bridge cycling is fundamental for this process, involving the attachment of myosin to actin, the power stroke (when myosin pulls actin towards the center of the sarcomere), and subsequent detachment and re-cocking of the myosin head, which requires ATP. The tension produced by these actions results in the force necessary for skeletal movement.