For a regular crunch, you'd lie on your back, using bodyweight for resistance. Here, you're kneeling, using the cable for resistance, allowing you to vary the weight. Hold the handle behind your head, elbows beside your ears. The cable also keeps the resistance constant throughout the movement. Stretch at the top, squeeze at the bottom. Breathe out as you slowly come down.
See also Advanced Cable Crunch.
with Romanian National Champion Paul Alexandru