Anyone who spends a lot of the day sitting could probably stand to strengthen their glutes. And the clam shell exercise is an excellent way to do just that.
But it also offers a whole lot more. This exercise—which is a staple in rehab and prehab physical therapy programs, as well as a fixture in some Pilates classes—ushers in a host of total-body benefits that go beyond the butt. Think: injury prevention, reduced pain, and overall better movement.
In case you’re not familiar, the clam shell involves lying on your side with your hips, knees, and ankles stacked on top of each other and knees bent to a 90-degree angle. Then, keeping your feet pressed together, you simply lift and then lower your top leg, performing a motion called hip abduction (basically using your hip muscles to move your leg away from your body). Watch a demo and you’ll understand where it gets its name: The exercise mimics the motion of its namesake sea creature.
The clam shell is simple, yes, but its benefits are seriously legit. Here we cover all you need to know about this super-effective move, including which muscles it works, what type of exercise it counts as, what you’ll gain by doing it on the reg, form errors to avoid, and tips for weaving it into your routine. Then we have a GIF and step-by-step instructions so you can try out the clam shell for yourself!
What muscles does the clam shell work?
Do enough reps of the clam shell and you’ll feel your gluteal muscles put to work. Specifically, this exercise really fires up your gluteus maximus (your biggest butt muscle) as well as your gluteus medius, a smaller muscle that forms your side butt, Femi Betiku, PT, DPT, CSCS, a physical therapist and Pilates instructor in Westchester, New York, tells SELF.
It also engages your tensor fasciae latae (TFL), one of the hip flexors, as well as your external obliques, core muscles that run along the sides of your torso, he adds. These two muscles get especially fired up if you use some type of resistance to complete the move—people most commonly do it with a mini-band placed above their knees—since that requires your body to work extra hard to help stabilize your trunk as you complete the clam shell motion.
What kind of exercise is the clam shell?
What box the clam shell ticks depends on your current activity level. If you’re new to exercise, it can be a muscular strength and endurance move, Dr. Betiku says. In other words, it can help your muscles get stronger and boost their ability to work for long periods of time. But if you’re already pretty active, then it’s more of a warm-up drill that can help engage your muscles before you use them more intensely during a workout. That’s because the glutes are one of the strongest muscles in the body, and in order to grow and strengthen them, you need resistance that’s heavy enough to really challenge them. Depending on your current strength level, a band may do this initially, but sooner or later, it won’t be up to snuff.