Weighted crunch (behind head)

Lie on a flat bench with knees bent, feet flat, and lower back lightly pressed into the bench. Grip a small plate with both hands and place it behind your head at the base of the skull; keep elbows slightly in and avoid pulling on the neck. Brace your core and exhale as you curl your upper spine off the bench, bringing ribs toward pelvis; keep the chin gently tucked. Pause briefly when shoulder blades are just off the bench, maintaining tension in the abs. Inhale and lower your torso back down under control until shoulder blades touch, without relaxing the core. Keep movement small and segmental (about 15\u201330\u00B0 of spinal flexion), and use a load you can control without pulling with the arms.