Weighted Decline Crunch

Set up on a decline bench with your feet hooked under the pads and a dumbbell held at your chest with both hands. Curl your ribs toward your hips the same way you would on a bodyweight decline crunch, but expect the decline angle and the added weight to compound — the stretch at the bottom is deeper and the top of the curl takes real effort to complete. Keep the dumbbell close to your chest rather than letting it drift toward your face, and keep your neck neutral throughout. If your hip flexors start doing more of the work than your abs, that's usually a sign the weight or the angle is asking more than your core can currently curl through cleanly.