2. Keeping the shoulders as parallel to the floor as possible, lift your shoulder blades off the floor. Do not aim an elbow at one knee. Hold for a second, and then lower to the starting position. Do 10 to 20, then drop knees to the opposite side and repeat.

Raised Leg Crunches:

Lie flat on your back with your knees bent and lower legs supported by a bench or chair. Your thighs should be at 90 degrees to the mat. Tilt the head forward to 45 degrees and hold your hands at your temples or cupped behind the ears. This is the starting position. Slowly crunch forward, breathing out as you do so, then slowly move back to the starting position while breathing in. Repeat, but don't relax between reps.

Never pull on your neck during a crunch. Doing so may injure your neck or upper back.

Bench Crunches:

These work upper, lower and oblique abs.

2. Bring your upper body to an upright position while pulling your knees into your chest. Hold for a second, and then return both the upper and the lower body to the starting position.