A study at San Diego State University measured the amount of muscle activation occurring with each of 13 common abdominal exercises and ranked the bicycle crunch as a top pick.
Muscles targeted include:
• External obliques: These muscles allow for rotation of the torso, flexion of the spine, and sideways bending and compression of the abdomen.
• Internal obiques: These muscles lie just below the external obliques and assist in providing flexing of the spinal column, sideways bending, trunk rotation and compressing the abdomen.
• Rectus abdominis: These “six-pack" muscles help to flex the spinal column, as well as acting as a stabilizer during movement.
Lie down on the floor face up, with your knees bent and fingertips lightly touching the back of your neck. Gently press the low back into the floor. Slowly lift the shoulders and upper back from the floor and then gently twist to the left, bringing your right elbow toward your left knee. Keep your right leg extended and off the floor. To complete one repetition, repeat this motion, twisting to the right, bringing your left elbow toward your right knee. Keep your left leg extended and off the floor.
Perform as many repetitions as you are able to complete with perfect form. This is considered one set. Take a brief rest break and repeat. Generally speaking, three sets to fatigue is a good beginning goal. Breathe evenly throughout the exercise.
Bicycle crunches can be performed every other day. Why not every day? If using proper intensity, then the abdominals will need a day of rest, just as with any other muscle group, in order to recover/repair. Remember that during exercise, muscles are torn down, while during periods of rest, they build and become stronger.
Be sure to move in a slow and controlled manner.
— Marjie Gilliam, Cox Newspapers