Killer Ab Exercises

Your rectus abdominus, or abs for short, is at the front of your body and is responsible for flexing your spine forward and also to the side. When your body fat levels are low enough--around 10 percent for men and 18 percent for women--your abs become visible and are often called your six-pack. There are lots of exercises you can perform for your abs but only a few that are challenging enough to be called ab killers.

Ab Wheel Roll Out

In 2010, ab wheels cost around $10 and are used to perform ab wheel roll outs, an advanced ab exercise. Kneel down, holding your ab wheel in both hands, and place it on the floor in front of you. Extend your hips and push the ab wheel as far away from you as you can while extending your whole body. Make sure your back doesn't arch excessively. Use your ab muscles to pull yourself back into the starting position and repeat. To make this hard exercise even harder, try performing it on your feet instead of on your knees. You will find the standing variation significantly harder than the kneeling one.

Hanging Leg Raises

You will need a sturdy overhead bar to hold onto for this ab exercise. Hold onto the bar and let your legs hang straight down. Using your abs, pull your knees toward your chest and perform a reverse crunch-type movement. Slowly lower your legs back down and repeat for the desired number of repetitions. If this isn't sufficiently challenging for you, try raising your knees until they touch your elbows. If your abs are strong, try keeping your legs straight and raising your feet up to the bar. This is called a pike leg raise and will give your abs a hard workout.

Inverted Sit-ups

This exercise can be performed using anti-gravity or inversion boots, available at sporting goods stores, or by suspending yourself carefully using monkey bars at a playground. Because you will be hanging completely upside down, inverted sit-ups are not suitable if you have high blood pressure or back problems and should only be performed if you are confident that whatever you are suspended from is strong enough to safely support your weight. Once you are inverted, perform your sit-ups in the usual fashion. To make inverted sit-ups even harder, hold a weight, such as a medicine ball.

One Arm/One Leg Planks

The plank is a popular ab exercise, but once you have developed a level of ab strength, it may become too easy. By supporting your weight on only one hand and one leg, this exercise will become much more challenging. Adopt the push-up position with your hands directly beneath your shoulders and your legs straight. Holding your abs tight and your spine rigid, lift your left leg and right leg off the floor. Hold this position for as long as you can without breaking form. Rest for a moment and then repeat using the opposite arm and leg.