How can I effectively perform a kneeling ab crunch to target my core muscles?

To effectively perform a kneeling ab crunch, start by kneeling on a soft surface with your feet flat on the ground. Place your hands behind your head or crossed over your chest. Engage your core muscles and slowly lean back, keeping your back straight. Then, contract your abs to bring your chest towards your thighs. Hold for a moment, then slowly return to the starting position. Repeat for desired reps to target your core muscles effectively.