Setup

Lie on your back with your knees bent and your feet flat on the floor. Straighten your arms and point them forward along the outside of your thighs, palms facing each other, as if you're about to slide them past your knees. Lift your head and shoulders slightly off the floor before the first rep and press your lower back into the mat.

Why the setup does the work here

Arms out in front change the whole feel of a crunch. With your hands by your head you can cheat by pulling your neck; here there's nothing to pull, so the only way up is with your stomach. The forward reach also gives you a clear target — your hands slide past your knees, or they don't — which keeps every rep honest without counting anything.

Technique

Crunch up and push your hands forward between your knees, like you're sliding them through a narrow gap. Your shoulder blades come off the floor; your lower back stays down. Breathe out as you push and squeeze your stomach hard for a second at the top. Lower under control until your shoulder blades almost touch the floor, then go straight into the next rep without resting on the mat. Keep your arms straight and your head in line with your chest the whole time.

Why technique decides everything here

The push is the rep, not the reach. If your arms shoot forward while your ribs stay flat on the floor, you've moved your shoulders and nothing else. What you want is your ribs travelling toward your hips while your hands travel past your knees — the arms just show you how far your body came. That's also why you stop short of the floor on the way down: touch down and the tension drops out of the muscle, stay an inch above it and your abs carry the load for the whole set.

Common Mistakes

Throwing the arms forward for momentum instead of curling the body. Sitting all the way up, which hands the work to your hips. Bending the elbows so the reach shrinks and the rep gets easier without you noticing. Holding your breath instead of blowing air out at the top. And resting flat between reps, which breaks the set into singles.

Where people lose results

This one is easy to fake because the hands move even when the body doesn't. Watch your shoulder blades, not your fingers — if they're not clearing the floor, the rep didn't happen. Keep the range small and the squeeze real, and when the top of your rep range gets comfortable, hold a light plate in your hands instead of adding more reps.