Flutter kicks are often used to work the lower abs. Generally, flutter kicks are performed at the end of an abdominal workout when the abs are fatigued. In reality, this exercise does very little for abdominal development. The main muscles worked are the hip flexors. So if you are trying to get the most out of your abs workout, there are better options.
Begin by lying on an exercise mat. Place your hands under your buttocks. This will help with leverage by reducing the load on the lumbar spine. Raise both legs approximately 15 to 20 inches off the floor. Contract your abs, then perform of series of alternating leg kicks (as if you are swimming in water). Try to keep your abs flexed during this exercise.
Lie on mat. Place hands under buttocks. Elevate legs.
Perform short kicks in alternating fashion. Maintain abdominal contraction.
Repeat the exercise as needed.