The clamshell exercise works the hips and glutes. It particularly targets and tones the gluteus medius, which forms the upper and outer part of the butt. This muscle gives your glutes shape and helps to stabilize the pelvis and hips, as well as moving the thigh away from the midline of your body (hip abduction) and rotating it outwards (hip external rotation).
If your glutes medius is weak, other muscles jump in to help out, which can lead to a cascade of problems including instability of the hips, knee and low back pain, injury, and poor movement mechanics.
Clamshells strengthen the gluteus medius and are one of the most effective exercises for injury treatment and prevention. It’s a classic exercise that often part of rehab programs. Clamshells can improve athletic performance in running-based sports, as it will strengthen the hips and improve running form and efficiency, helping you to run stronger and better.
The clamshell exercise is also simply called the clam or more technically – side-lying hip external rotation.
Keep you torso and pelvis steady as you raise your knee. It’s a common mistake to tilt the torso forward or for the hips to roll backward as you execute the movement. Keeping your core engaged will help keep your upper body stable.
Variations: You can make clamshells more challenging by looping a resistance band around your thighs, just above the knees. Another way to increase difficulty is to progress to the side plank clamshell, where you’re in a similar position except the bottom arm is bent and your elbow is directly underneath the shoulder.