The clamshell... one of the most highly prescribed gluteus medius exercises by physical therapists, but also highly debated. Why?
Some people argue that the gluteus medius is best strengthened during isolated hip abduction, which has been proven correct during research studies looking at EMG data for this particular muscle activation. But is strict muscle activation the only thing we're striving for when performing exercises?
I would argue that another reason to perform exercises is to retrain your body in different movement patterns. In this case, it doesn't so much that you are isolating a particular muscle (gluteus medius), but rather that you are training the body to perform a particular motion. The motion in question: hip external rotation.
When do we need to perform hip external rotation, you might ask. Good question. I would like to make a case for training hip external rotation to prevent or un-learn medial collapse.
For those who are unfamiliar, medial collapse is the term that describes in the inward motion at the knee during close chain knee flexion. In more basic turns, if you squat or stand up from a chair and your knees tend to move in towards each other, that is medial collapse.
So how do we avoid or un-learn medial collapse? Well, a lot of that comes from external rotation at the hip. It is common for PTs to cue patients to rotate through the hip to keep their knees in line with their feet during squatting. This motion is arthokinematically similar to a clamshell exercise. The clamshell could be considered level one, and then you would move to a standing clamshell as level two.
So while the clamshell exercise may not be number one for recruiting gluteus medius in order to strengthen it, I still feel that the exercise is beneficial for learning hip external rotation in order to restore proper hip-knee-ankle-foot mechanics during close chain mobility.
What are your thoughts? Do you perform or prescribe clamshells as an exercise? Why or why not?