What is the difference between using a box or bench versus a wall for supine 90-90 exercises?

• A. Shelf or box under the feet may fire distal hamstrings; use the wall to engage proximal hamstrings.
• B. Shelf or box under the feet activates hip flexors primarily.
• C. Wall engagement suppresses proximal hamstrings.
• D. Shelf under the feet is always better than the wall.

Answer: (A)