Crunches have been around forever and have proved their worth. However, guys like to throw their arms forward as they perform them, using momentum to bring their shoulder blades off the floor. This renders the move less effective. The solution is simple: Place your arms behind you so you can’t use them.

How to Do It

1. Lie on your back on the floor with your knees bent. Reach your hands over and behind your head and down your back, placing your palms on your opposite shoulder blades.

2. Squeeze your abs to crunch your torso off the floor, trying to bring your elbows to your knees. Pause for a second, then slowly lower yourself back to the floor.

Because your hands aren’t thrown forward or cradling your head, as people often have them on crunches, you can’t thrust or pull yourself up (the latter example also risks injury to your neck).

In addition, the cross- back crunch gives you feedback on your form. You’ll know when your shoulder blades are off the floor—the correct amount of movement—because you won’t be lying on your hands.

Quick Tip

Don’t bounce your reps on crunches. pause at the top and bottom of each rep to keep tension on the abdominal muscles.