Side-Lying Clamshell
Clamshell is the gold-standard isolation exercise for the glute medius. Boren and colleagues (2011) measured a clamshell variation at 77 percent of maximum voluntary contraction for the glute medius, putting it among the highest-activation exercises in their rehabilitation EMG study. Crucially for piriformis sufferers: when the glute med is weak, the piriformis (a smaller, deeper external rotator) takes on stabilising work it was not built for and tightens. Strengthening the clamshell directly is the upstream fix.
Illustration · follow the steps below for the actual technique
How to do it
- 1
Lie on your right side with knees stacked, bent to about 45 degrees, feet stacked
Side-lying start
- 2
Rest your head on your right arm. Keep your hips stacked vertically, no rolling back
Hips stacked
- 3
Keep your feet together and lift your top (left) knee toward the ceiling
Open the clam
- 4
Pause at the top for one second, feeling the squeeze in the side of your top hip
Squeeze and pause
- 5
Lower with control. Do 15 reps, then roll over and repeat on the other side
Control the lower
The evidence
Clamshell is the gold-standard isolation exercise for the glute medius. Boren and colleagues (2011) measured a clamshell variation at 77 percent of maximum voluntary contraction for the glute medius, putting it among the highest-activation exercises in their rehabilitation EMG study. Crucially for piriformis sufferers: when the glute med is weak, the piriformis (a smaller, deeper external rotator) takes on stabilising work it was not built for and tightens. Strengthening the clamshell directly is the upstream fix.
Citation: Boren K, Conrey C, et al. (2011). Electromyographic analysis of gluteus medius and gluteus maximus during rehabilitation exercises. International Journal of Sports Physical Therapy