Which of the following is the primary function of the skeletal system?

The NASM CPT7 Study Guide states that one of the skeletal system’s core functions is to provide the rigid framework that supports the body and serves as levers for movement when acted upon by muscles. Specifically, “Human bones act as attachment sites and levers (rigid rods) to produce movement when muscles contract.” Muscles generate the force, but it is the skeletal structure—through the interaction of bones, joints, and connective tissues—that converts that force into purposeful motion. This lever system can be first-, second-, or third-class, with most human movements involving third-class levers. The other options describe the functions of different body systems: generating internal tension is the role of the muscular system, responding to external stimuli is primarily the nervous system’s role, and kinesthetic motor control involves integration between the nervous and muscular systems. Thus, the primary skeletal function relevant here is acting as levers in conjunction with muscle contractions to facilitate movement.