Tiny move, huge glute med burn.
Keep your hips stacked and still. If your whole body rolls back, you're cheating it.
The clamshell zeroes in on the glutes, particularly the glute medius on the side of your hip, by rotating the top knee open against gravity while your feet stay glued together. Working one side at a time with hips stacked strips out every possible cheat, which is why physios and strength coaches both lean on it. It is the pre-squat activation move that makes knees track and hips feel stable under load.
Front of the session. As an activation drill before squats, lunges or runs, they switch on the glute med so it actually shows up when the heavy work starts.
Higher reps work best, around 15 to 25 per side, done slowly. It is about quality contractions in the glute, not load, so stop counting reps that involve your whole body rocking backward.
You are chasing range your hip does not have yet. Keep hips and shoulders stacked, open the knee only as far as you can without moving anything else, and let the range grow over weeks.
