Final answer:
Yes, the length of the muscle's lever arm does change throughout a joint's range of motion, which in turn affects the force required by the muscle to perform an action.
Step-by-step explanation:
The student's question pertains to whether the length of the muscle's lever arm changes throughout a joint's range of motion (ROM). The correct answer is true. In anatomical terms, as a joint is flexed, the pivot point and hence the perpendicular lever arm can change. This alters the mechanical advantage of the system, affecting the amount of force a muscle must exert. The biceps muscle, for example, will exert different amounts of force to hold up an object as the forearm angle changes due to the changing length of the lever arm during flexion and extension. Additionally, the muscle's force capacity changes with its length; it is reduced when the muscle is shorter as opposed to when it is more stretched.