Final answer:
The correct statement is that the further the force is from the joint axis of rotation, the harder the muscle must work to counter the force, since the moment of inertia increases with the square of the distance from the rotation axis.
Step-by-step explanation:
When working to increase the strength of muscles, the concept of the moment of inertia suggests that C. The further the force is from the joint axis of rotation, the harder the muscle must work to counter the force. This is because the moment of inertia is dependent on the distribution of mass relative to the axis around which it rotates, and it increases with the square of the distance from the rotation axis. To overcome a greater moment of inertia, the muscles must generate a greater torque. This involves applying force at a greater distance from the joint, which effectively increases the lever arm length, contributing to a higher torque requirement.
For example, holding a weight closer to your body requires less force because the moment of inertia is smaller. However, as you extend your arm and increase the distance of the weight from the joint axis (such as the elbow), the moment of inertia increases and you must apply more force to maintain the same angular position against gravity. This concept is crucial in designing effective workout routines to enhance muscular strength and is exemplified by exercises like bicep curls, where the muscle must work harder to lift the weight as it moves further from the elbow joint.