What muscles are involved in trunk extension?

Study for the NPTE Physical Therapist Assistant Exam. Ace the test with comprehensive flashcards and multiple-choice questions. Each query offers hints and detailed explanations. Get thoroughly prepared for your examination!

Trunk extension primarily involves the erector spinae and quadratus lumborum muscles. The erector spinae group, which includes the iliocostalis, longissimus, and spinalis, plays a key role in extending the spine and maintaining an upright posture. These muscles run along the length of the spine and allow for back extension as well as lateral flexion and rotation of the trunk.

The quadratus lumborum, located in the lower back, assists with lateral bending and also contributes to extension of the lumbar spine when both sides contract. This combination enables effective extension of the trunk, especially when engaging the muscles in activities such as standing up straight from a bent position or arching the back.

Other options present muscles that do not primarily function in trunk extension. For example, the rectus and internal oblique muscles are more involved in flexion and rotation of the trunk rather than extension. The psoas major and external oblique do not contribute to extending the trunk, as they primarily assist in flexing the hip and trunk rotation, respectively. Therefore, identifying the correct muscles that specifically facilitate trunk extension underscores the understanding of spinal mechanics and movements.

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