Final answer:
Excessive arching of the back indicates incorrect performance of the trunk stability roll, with core muscle engagement being crucial for correct execution and maintaining good posture. Option C is correct.
Step-by-step explanation:
The trunk stability roll is being performed incorrectly if the person experiences Excessive arching of the back (C). This excessive arching can be a sign that the core muscles are not being sufficiently engaged to stabilize the trunk during the exercise.
Good posture requires that the person's center of gravity is aligned with the pivot point in the hips to avoid unnecessary strain on the back and for efficient muscle activation.
More specifically, improper technique that includes minimal activation of core muscles (B) and backward displacements due to inadequate foot positioning contribute to instability and ineffective exercise performance.
Proper trunk stability exercises involve symmetry in weight distribution, a smooth and controlled movement, and effective engagement of the core and abdominal muscles to maintain a proper alignment.