What is the primary purpose of using the box in spinal extension and flexion on the reformer?

• A. A stable base to anchor the pelvis and offer varied leverage for safe sequencing of extension and flexion with precise spinal control.
• B. It is primarily for upper body workouts and does not affect spinal alignment.
• C. It should be used only when the spine is fully extended to the hip joint.
• D. It makes the spine move without pelvis stabilization during movement.

Answer: (A)