Side-Lying Clamshell
Clamshell is the gold-standard isolation exercise for the glute medius. Boren and colleagues (2011) measured clamshell progression 4 at 77 percent of maximum voluntary isometric contraction for the glute medius, one of five exercises above 70 percent among the 18 they tested. Why it matters for piriformis pain: Tonley and colleagues (2010) describe a patient whose weak hip abductors and external rotators let the thigh drop into adduction and internal rotation on a step-down, reproducing his symptoms. They read that as the piriformis being overstretched, not shortened, and treated it with strengthening alone. Training the glute med to control that drop is the upstream work.
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 clamshell progression 4 at 77 percent of maximum voluntary isometric contraction for the glute medius, one of five exercises above 70 percent among the 18 they tested. Why it matters for piriformis pain: Tonley and colleagues (2010) describe a patient whose weak hip abductors and external rotators let the thigh drop into adduction and internal rotation on a step-down, reproducing his symptoms. They read that as the piriformis being overstretched, not shortened, and treated it with strengthening alone. Training the glute med to control that drop is the upstream work.
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