Maybe you’ve tried it in a Pilates class, or perhaps your physical therapist gave it to you as a take-home exercise due to lingering pain, weakness, or tightness.
There’s a reason why the clamshell, the difficult (and also at times fun) exercise is so popular. It simultaneously strengthens the glutes and hips, which are not easy areas to target. It’s also a great exercise for athletes and can be used as a warmup. Finally, it’s easy enough to modify, making it accessible to everyone.
But what is the clamshell exercise, exactly, and how do you do it? What do modifications look like, and how do you know if you’re doing it correctly? Here’s everything you need to know.
What Is the Clamshell Exercise?
The clamshell is a strengthening exercise in which you lie on your side, bend and stack up your knees, and open and close them. The position your legs are in makes them look like a clamshell. “Clamshells target and strengthen hip and glute muscles, the hip abductor muscles (glute medius being the most obvious one) which are super important for balance and stability,” explains Peloton instructor Selena Samuela.
Benefits of the Clamshell Exercise
The benefits of clamshell exercises include strengthening hip and glute muscles and are also excellent for warming the body up before a workout. “This is especially true for workouts that require lower body movement like cycling or running or sports like tennis or squash or golf that use lateral movement, as activating glute medius for lateral movement in key,” Selena says. “Those warmups are usually done with bodyweight only and then you’ll progress with a band.”
If you want to work the core, Selena suggests adding a hip bridge (which looks a bit like a side plank) to deeply engage the core as well.
What Muscles Do Clamshell Exercises Work?
According to Ingrid Anderson, doctor of physical therapy and owner of Intown Physical Therapy in Atlanta, the clamshell exercise primarily works the hip rotators and hip abductors. “The hip abductors include the gluteus medius and minimus, which are critical for knee stability, especially while training,” she says. “Strong and activated hip abductors control the femur’s movement underneath the patella.”
Some variations of clamshell also work the core, per Selena.
How to Do a Clamshell Exercise
So, how do you do a clamshell exercise? Here’s a step-by-step guide, per Anderson.
1. Lie on your side with your head supported. This can be done with a pillow, yoga block, or your arm. “The support of the head is not necessary, but prevents quitting due to neck fatigue,” says Anderson.
2. Roll your hips slightly forward and place the palm of your top hand on the floor. You’ll want to rest that hand very gently like you’re pressing on an egg you don’t want to break. “This activates your transverse abdominis muscle,” Anderson says.
3. Open your knees. Do this with your heels together and make sure to not lean back at all. “The tendency is to lean back to increase the range of motion of the exercise,” says Anderson. “Understand that all you need to do is to open the knees as far as they go without leaning back.”
4. If you can’t do the exercise without leaning back, modify. If you keep leaning back, move to a wall or do it on the couch where you can’t lean back. “And if you find you cannot lift your knee at all without leaning back, put a pillow between your knees,” Anderson adds. “As long as you are feeling the work on the outside of your hip (side butt), you are doing it right.”
5. Do two sets of clamshells to fatigue. While the duration of this exercise will vary based on your goals, Anderson says that in general, it’s best to do two sets of clamshells to “fatigue” or until you’re too tired to keep your good form up.
“If your challenge is endurance, that number should be between 15-30,” she says. “If you’re working on strength, the reps to fatigue should be between five and eight. If you can bang out 30 full-range clamshells without leaning back, you need to modify to make them harder. For endurance, you can do them five to six days a week, while if you’re working to build strength, you should do three to four days a week, or every other day.”
Clamshell Exercises: Variations and Modifications
One of the reasons why the clamshell is such a great exercise to incorporate into your routine is because it’s easy to modify.
To make clamshells easier, Anderson suggests reducing the range of motion by putting the pillow between your knees. “You can reduce the range of motion even more by simply trying to open the knees until you feel your side-butt muscles activate,” she says. “Bring your knees closer to your chest to make it a little easier.”
If clamshell is easy for you, you can also modify it to make it more difficult. “Follow the same directions as with the original clamshells, but after you open the knees, keep the top knee in place and lift your top heel to the level of your top knee, and then lower the entire leg together,” she says. “This one works the abductors slightly more, as well as challenging the external rotators.”