Banded Bicycle Crunch

The bicycle crunch combines trunk flexion and rotation, which is the pairing that actually reaches the obliques rather than working the rectus abdominis alone. Adding a resistance band around both feet loads the knee drive, so the hip flexors and the lower abdominals meet resistance on every repetition instead of moving through empty space. That is the one thing the bodyweight version cannot offer once you can perform it comfortably. The band also keeps the extended leg honest, since letting it drop releases the tension immediately. Speed remains the enemy: performed quickly, momentum carries the torso across and the obliques barely contract, so move deliberately. Rest the fingers lightly against the sides of the head rather than lacing them behind it. Use a light band to begin with, because the resistance is applied at the end of a long lever and even a thin one changes the difficulty considerably. Keep the extended leg hovering rather than resting it between repetitions.