Clamshell
Opening the top knee from side-lying with feet together — targeted activation for the deep glutes that control the knee in running.
Also called: clam, clams
Illustrations: Exercise data by RepDB (repdb.co)
Setup
Lie on your side, knees bent about 90 degrees, feet in line with your spine, head resting on your arm.
How to do the Clamshell
- Keeping feet touching, lift the top knee like a clam opening.
- The pelvis stays stacked and still — only the hip rotates.
- Lift as far as you can WITHOUT rolling backward.
- Lower slowly; feel the work in the side of the hip.
Clamshell muscles worked
The Clamshell works the glute medius and deep hip rotators.
Common Clamshell mistakes
- Rolling the pelvis backward to fake a bigger range.
- Rushing — this is a small, precise movement.
- Feeling it in the front of the hip: reset the pelvis position.
Scale it
Easier: Smaller range, no band.
Harder: Add a mini-band around the knees or hold the top for 2 seconds.
Pairs well with
Lateral Band Walk
Sideways steps against a mini-band — glute medius strength for hip and knee control on the run.
Side Plank
The straight-body hold on one forearm — lateral core strength that stabilizes the pelvis every single running stride.
Side Plank Hip Abduction
Lifting the top leg while holding a side plank — combines core stability with hip strengthening.
Side-Lying Leg Raise
Raising the straight top leg from side-lying — simple, honest glute-medius strength work.