The ab kick-out works the rectus abdominis in the middle of your abdomen and the deeper transversus abdominis. Besides increasing muscle tone, the exercise also improves your posture, stability and balance. Core exercises like kick-outs have the added benefit of helping prevent lower back pain and injury. As always, talk to your doctor before trying the ab kick-out, especially if you suffer from a prior back injury or health condition.
Correct form is critical when performing kick-outs -- using the proper form prevents injury and ensures you're working the right muscles. It's better to complete fewer kick-outs properly than fulfill a specific number of repetitions with poor form. To correctly perform a kick-out, sit down on the floor with your legs straight out in front of you. Hold your torso taut and bend your knees into 90-degree angles as you lift your legs to chest-height. Lean back until your torso is a 45-degree angle from the ground. Bend your arms and hold them close to your chest, keeping your fists beneath your chin. Slowly straighten your legs and lower your upper body toward the floor at the same time. Keep lowering yourself until your torso and feet are about five inches above the ground. Reverse the movement and return to the starting position. Repeat for a total of 15 repetitions or until you reach failure. Your abdominals should do all of the work when doing kick-outs -- not your back or hip flexors. To further tax your abdominal muscles, hold your legs out for about six seconds before bending them back into the starting position.
Changing how you perform kick-outs adds variety to your workout routine as well as changing the challenge of the exercise. Perform the abdominal kick-out exercise while sitting on an elevated bench with your hands grasping the edges of your seat. To increase the intensity of the exercise, hook an exercise pulley to your ankles or hold a dumbbell between your feet. You can also loop an exercise band beneath the bottoms of your feet to add resistance as you kick out your legs. Add more exercise sets as your strength improves.
When you're doing an ab kick-out, don't let your feet touch the floor as you kick out and lower them toward the ground. Breathe properly by exhaling as you kick your legs out and inhaling when you pull your legs back in. For maximum results, perform the ab kick-out slowly. Keep your abdominal muscles tight and contracted throughout the entire exercise.
Gradually work your way up to the full 15 repetitions if you are new to exercise. Increase the reps as your core strength improves and you master the movements of the ab kick-out. Never perform this exercise two days in a row, which can cause muscle strain and pulls. Your abdominal muscles require a full 24 hours or recovery to grow stronger and repair themselves. Use just a light amount of weight -- between 5 and 15 pounds -- if you add additional weight to the abdominal kick-outs. Adding too much weight can lead to a hernia.