Final answer:
In the context of a squat, posterior pelvic tilt pairs with flexion of the lumbar spine as they both occur in the sagittal plane. The erector spinae muscles contribute to postural support and extend the vertebral column.
Step-by-step explanation:
At the bottom of a squat, posterior pelvic tilt is paired with flexion of the lumbar spine. Flexion and extension are movements occurring within the sagittal plane, which involve the anterior or posterior movement of body parts. When discussing the vertebral column, flexion refers to an anterior bending of the neck or body, while extension refers to a motion that straightens or bends the body backward. The lumbar spine, being part of the vertebral column, adheres to these definitions; thus, in the context of a posterior pelvic tilt during a squat, the lumbar spine is typically in a state of flexion.
The erector spinae plays a crucial role in stabilizing and moving the spine. It provides postural support and is involved in extending the vertebral column, among other actions. Understanding the functioning of these muscles and spinal movements is essential for health studies, particularly regarding exercise and human biomechanics.