ACSM Personal Trainer Certification Practice Exam 2025 - Free Personal Trainer Practice Questions and Study Guide

Lateral flexion is the correct answer because it specifically refers to the movement of bending the body sideways, which results in a decrease in the angle between the vertebrae along the side of the spine. When performing lateral flexion, the spine bends toward one side, reducing the angle of the torso in relation to the pelvis. This movement is commonly involved in tasks such as reaching for an object on the side or performing side bends in exercises.

In contrast, extension refers to increasing the angle of the spine, usually when standing up straight or leaning back. Hyperextension goes even further by extending the back beyond its neutral position, creating a larger angle. Adduction, on the other hand, pertains to moving a limb or body part toward the midline of the body, which is not directly related to the motion of bending the spine laterally. Therefore, lateral flexion is the movement characterized by a decrease in the angle of the spine during side bending.