Which statement correctly describes trunk rotation mechanics?

Which statement correctly describes trunk rotation mechanics?

• A. External Oblique (contralateral rotation) and Internal Oblique (ipsilateral rotation) acting together
• B. Erector Spinae causes rotation
• C. Rectus Abdominis causes rotation
• D. Latissimus Dorsi causes rotation

Answer: (A)

Trunk rotation is driven mainly by the oblique muscles of the abdomen. The external obliques produce rotation to the opposite side, while the internal obliques produce rotation to the same side. When twisting in a given direction, these two groups on opposite sides work together to generate that rotation. For example, turning to the right involves the left external oblique (causing rightward, contralateral rotation) and the right internal oblique (causing rightward, ipsilateral rotation). So describing that the external oblique provides contralateral rotation and the internal oblique provides ipsilateral rotation, acting together, accurately reflects how rotation is produced. Other muscles listed aren’t the primary rotators: the erector spinae mainly extend and help with lateral flexion and some rotation as a secondary effect; the rectus abdominis mainly flexes the trunk; the latissimus dorsi largely moves the shoulder and assists with overall trunk movements but not primary rotation.

Trunk rotation is driven mainly by the oblique muscles of the abdomen. The external obliques produce rotation to the opposite side, while the internal obliques produce rotation to the same side. When twisting in a given direction, these two groups on opposite sides work together to generate that rotation. For example, turning to the right involves the left external oblique (causing rightward, contralateral rotation) and the right internal oblique (causing rightward, ipsilateral rotation). So describing that the external oblique provides contralateral rotation and the internal oblique provides ipsilateral rotation, acting together, accurately reflects how rotation is produced.

Other muscles listed aren’t the primary rotators: the erector spinae mainly extend and help with lateral flexion and some rotation as a secondary effect; the rectus abdominis mainly flexes the trunk; the latissimus dorsi largely moves the shoulder and assists with overall trunk movements but not primary rotation.