The Clamshell Exercise

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The clamshell exercise is so named because of the way your lower body resembles a clamshell while you do it. Clamshell exercises are used in physical therapy clinics, Pilates classes and as part of general strength and toning routines. You can do the clamshell with no equipment and very little space.

Basic Technique

The basic clamshell technique calls for you to lie on your side with your knees slightly bent, keeping your legs and ankles together. You can rest your head on an outstretched arm during the exercise. Place your other hand on your hip, and then open and close your knees like a clam by lifting your top knee up until its parallel with your hip. Keep your feet together throughout the exercise, controlling your leg by tightening all of the muscles involved in the movement as if someone is pushing against your knee while you are pressing it up. Perform 10 to 15 repetitions on one side and repeat by rolling to the opposite side.

Resisted Clamshells

Add resistance to the clamshell in a couple different ways. First, set up in the normal clamshell position, while holding a weight plate on the outside of your top thigh or knee with your top hand. Move your top leg up and down slowly, allowing the weight to supply resistance. Alternatively, loop a short resistance band around your calves to provide resistance between your legs as you perform the clamshell.


The clamshell exercise serves various functions, including strengthening your hips, inner and outer thighs, stabilizing your pelvic muscles and toning your buttocks. If desired, you can shift your position slightly to emphasize a particular muscle. The clamshell exercise is also used by some therapists to reduce lower back pain by strengthening the core and lower back muscles. Although the clamshell does not directly work your abdominal muscles, you can actively engage your core muscles while performing the exercise by pulling your belly button toward your spine.

Clamshell Ball Crunch

Another exercise places your body in a different position, but is also referred to as the “clamshell.” However, this exercise focuses on strengthening the abdominal muscles. The clamshell ball crunch has you situated on your back with a stability ball held firmly between your lower legs. Place your hands behind your head and then lift your legs off the floor while simultaneously lifting your shoulders, resembling a clamshell. Engage your core by pulling your belly button toward your spine. Perform one or two sets of 10 to 15 repetitions.