Final answer:
The trunk extension is executed through the erector spinae muscle group, with special involvement from the iliocostalis and multifidus muscles which contribute to the movement of the vertebral column.
Step-by-step explanation:
Trunk Extension and Muscles Involved
Trunk extension primarily involves the erector spinae group which consists of the iliocostalis, longissimus, and spinalis muscle groups. These groups are responsible for the flexion, lateral flexion, extension, and rotation of the vertebral column. Specifically, the iliocostalis lumborum assists with the lumbar region, and the iliocostalis thoracis deals with the thoracic region. Additionally, the multifidus muscle of the lumbar region helps in extending and laterally flexing the vertebral column. Other important muscles contributing to trunk movement include the longissimus thoracis, which is part of the longissimus group situated intermediately within the erector spinae.