Most internal torques controlling joint motion at mid-range are created by what?

Most internal torques controlling joint motion at mid-range are created by what?

• A. Passive ligaments only
• B. Concentric or eccentric muscle activation
• C. Bone compression only
• D. Ground contact only

Answer: (B)

Internal joint torques at mid-range come primarily from muscles acting across the joint. When a muscle shortens (concentric contraction), it generates a torque that drives the joint in the direction of the contraction. When a muscle lengthens under load (eccentric contraction), it still produces a torque that controls or slows motion, helping to stabilize the joint. At mid-range, muscles can produce strong, favorable force-length relationships and moment arms, so their torque contribution dominates. Passive ligaments tend to contribute more near end ranges when they become taut, so they’re not the main source at mid-range. Bone compression is a result of forces transmitted through the limb and does not by itself create a turning effect about the joint axis. Ground contact can influence motion via external forces, but that’s external torque, not an internal muscle-driven torque. So the best answer is that active muscle activation—concentric or eccentric—creates most of the internal torques governing joint motion in mid-range.

Internal joint torques at mid-range come primarily from muscles acting across the joint. When a muscle shortens (concentric contraction), it generates a torque that drives the joint in the direction of the contraction. When a muscle lengthens under load (eccentric contraction), it still produces a torque that controls or slows motion, helping to stabilize the joint. At mid-range, muscles can produce strong, favorable force-length relationships and moment arms, so their torque contribution dominates.

Passive ligaments tend to contribute more near end ranges when they become taut, so they’re not the main source at mid-range. Bone compression is a result of forces transmitted through the limb and does not by itself create a turning effect about the joint axis. Ground contact can influence motion via external forces, but that’s external torque, not an internal muscle-driven torque. So the best answer is that active muscle activation—concentric or eccentric—creates most of the internal torques governing joint motion in mid-range.