Pull-ups are body weight exercises that work multiple upper body muscles, such as the latissimus dorsi, pectorals and biceps. For a variation to your normal ab workouts, use a pull-up bar to work your lower rectus abdominis and obliques. The obliques are found on the sides of your stomach.
Knee raises, or reverse crunches, are basic pull-up bar abdominal exercises. After grasping the bar with an overhand, shoulder-width grip, let your legs hang straight down. Keeping your upper body still, lift your legs, bend your knees and parallel your thighs to the floor. After squeezing your abs and holding for a full second, slowly lower your legs back down and repeat. For a variation, keep your legs straight. To increase the challenge, wear ankle weights.
The leg-hip raise is a progression to the knee raise. While hanging from the bar, lift your legs, bend your knees and then tuck your hips under your body. As you do this, lift your knees toward your chin and squeeze your abs forcefully. Slowly lower your legs all the way down to a straight position and repeat. In similar fashion to the knee raise, keep your legs straight to increase the intensity and wear ankle weights to increase the resistance.
Scissor kicks work your abs in an alternating motion. After grasping the bar, raise your right leg in front of your body until it parallels the floor. As you lower it, raise your left leg the same way. Lift each leg up and down in a scissor motion. For an easier variation, bend your knees when you raise your legs. To increase the challenge, keep your legs straight and lift them higher than parallel to the floor. When doing this exercise, it is going to be tempting to swing your body for momentum. Make sure to keep your upper body as still as possible.
Hanging oblique raises work your obliques by angling your lower body. Grasp the bar and let your legs hang straight down in the normal starting position. Keeping your upper body still, raise your knees up and toward your left shoulder. After holding for a second, slowly lower your legs back down and repeat on your right side. Alternate back and forth with each repetition.
The windshield wiper is an intense ab exercise that works the obliques. While hanging from the bar, raise your legs straight in the air and hold your shins right in front of the bar. Keeping your upper body still, lower your legs to your right side as far as possible, then lift them up and move them to your left side. Alternate back and forth in a steady, but controlled motion. Keep your arms and legs straight throughout.