Define torque and explain how it relates to the biomechanical advantage of a lever in human movement.

• A. Torque measures speed and distance.
• B. Torque is the product of force and lever arm, and lever classes affect mechanical advantage.
• C. Torque depends only on mass.
• D. Torque applies only to machines.

Answer: (B)

Torque is the turning effect produced when a force acts at a distance from a pivot, like a joint axis. It depends on both how hard you pull and how far from the joint you pull—the perpendicular distance from the joint to the line of action of the force (the lever arm). The longer that lever arm, the greater the torque for the same muscle force, so the joint rotates more easily.

In human movement, bones and joints form lever systems, with muscles providing the forces. The arrangement of where the muscle attaches relative to the joint determines the lever arm length, and thus the torque you can generate. This is how biomechanical advantage works: it’s the effectiveness of a given muscle force to produce rotation about the joint, driven by the ratio of the effort arm to the resistance arm. If the effort arm is longer than the resistance arm, you get a mechanical advantage (more torque for the same force). Humans often trade some mechanical advantage for speed and range of motion in many movements, but the core idea remains that torque equals force times lever arm, and lever class shapes how that torque translates into movement.