Massage & Bodywork Licensing Examination (MBLEx)

What movement will lengthen the fibers of the quadratus lumborum on the right side of the body?

1. Hip elevation

2. Lateral flexion to the right

3. Lateral flexion to the left

4. Extension of the vertebral column

The correct answer is: Lateral flexion to the left

To understand why lateral flexion to the left lengthens the fibers of the quadratus lumborum on the right side, it's essential to consider the anatomical function of the quadratus lumborum. This muscle runs from the iliac crest to the lumbar vertebrae and plays a crucial role in stabilizing the pelvis and spine during movements. When the body performs lateral flexion to the left, the right quadratus lumborum is stretched. This occurs because the muscle is contracting to stabilize and aid in the movement while being elongated in the opposite direction. As the body bends to the left, the right side of the torso and the quadratus lumborum must lengthen to accommodate this movement. In contrast, hip elevation would engage and shorten the quadratus lumborum, as would lateral flexion to the right by actively pulling the muscle on that side. Extension of the vertebral column primarily engages muscles along the back, but it does not specifically target the lateral muscles, leading to less direct influence on the lengthening of the quadratus lumborum compared to lateral flexion to the left. Thus, understanding these mechanics clarifies why lateral flexion to the left effectively lengthens the right quadratus lumborum.