Final answer:
Low activity back extensors, slight activity of psoas, and slight activity of external oblique point to the role of abdominal wall muscles in posture and trunk movements.
Step-by-step explanation:
Low activity of the back extensors, slight activity of the psoas, and slight activity of the external oblique are all related to the muscles of the abdominal wall. These muscles help maintain posture and stability, as well as contribute to movements of the trunk.
The back extensors, such as the multifidus muscle, help extend and laterally flex the vertebral column, while the psoas muscle assists in hip flexion. The external oblique muscle, located on the sides of the abdomen, helps with rotation and lateral flexion of the trunk.
In summary, the low activity of the back extensors, slight activity of the psoas, and slight activity of the external oblique indicate the involvement of the muscles of the abdominal wall in maintaining posture and allowing certain movements of the trunk.