An isolation exercise for the obliques using a bar.
Lie down on a bench or exercise ball and press the feet against the floor.
Lift the torso slightly.
Hold one handle of the lower block with extended arms.
As you exhale, turn your torso to the right.
Pause for 1-2 seconds.
As you inhale, return to the starting position and repeat the crunch to the left.
Keep your torso and back straight, don't swing.
The straighter your arms are, the more load will be placed on both abs and arms.