Core Ab Exercises

The core muscles of your body include more than just your abdominals. You should also do exercises to target the glutes, inner thighs, outer thighs and the abs, including the oblique abdominal muscles of the waist. All of the muscles from below your chest to the bottom of your torso are considered your core because they stabilize your spine and work as your power center. Do two to three sets of core exercises with a 30 second rest between them.

Straight-Leg Bicycles

Straight-leg bicycles are one of the most effective exercises for the abs and they also burn calories because they are done quickly, notes Jeanine Detz in her book, "Ultimate Core Ball Workout." Straight-leg bicycles works your abs, obliques and inner thighs. Straight-leg bicycles use an exercise ball to add intensity.
Lie on your back and extend your legs straight to the ceiling. Place a stability ball between the lower parts of your legs. Bend your elbows and place your palms behind your head. Crunch your head, neck and shoulders off the floor. Rotate your shoulders to the left and twist your hips to the right. This will bring your right elbow toward your left knee. Allow the ball to roll between your legs as you twist, but do not drop it. Twist in the opposite direction. Continue twisting without stopping or putting your shoulders down. Do up to 20 reps per side.

Leg Adduction/Abduction

This exercise works your glutes, inner thighs and outer thighs. You should keep your abs tight throughout the exercise to stabilize your spine.
Stand up straight and place your hands on your hips to do the leg adduction/abduction exercise. You can hold the back of a chair or place your hand on a wall for balance if you need to. Tuck your hips and squeeze your abs. Raise your left leg to the side toward the ceiling. Lower your leg and bring it across your body in front of your right leg. Keep both legs straight, but bend your knees slightly to soften your knee joints. This works the adductor and abductor thigh muscles of your left leg. Do eight reps per leg, recommends Thomas Boettcher in his book "Core Training for Greater Strength and Better Health."

Reverse Crunches

Lie on your back to do reverse crunches. The reverse crunches target your lower abs and inner thighs, though they will work your entire abdominals. Reverse crunches also use an exercise ball to increase intensity.
Squeeze a medicine ball, stability ball or pillow between your knees to work your thighs. Place your arms at your sides on the floor, palms down. Raise your legs straight to the ceiling so that they are perpendicular to the floor. Press your lower back flat. Lower your legs toward the ground, but do not allow your back to arch. Raise your legs back up once you reach the point that your abs are no longer strong enough keep your back down. Do not stop squeezing the ball or pillow.