Clam Shell
The clam shell activates the gluteus medius for hip stability, supporting HYROX Sandbag Lunges and knee health during running.
Definition
The clam shell is a compound hip-abduction exercise performed lying on your side with knees bent and feet together. You open your top knee like a clam shell while keeping your feet in contact. It is a targeted glute medius activation exercise used to improve hip stability and prevent knee valgus in HYROX® movements.
Technique & Form
- Starting position: Lie on your side with knees bent at 45 degrees, feet stacked. Head resting on your lower arm.
- Open: Keeping your feet together, rotate your top knee upward as far as possible. The movement comes from the hip, not the spine.
- Top position: Hold for 1-2 seconds, squeezing the glute medius.
- Close: Lower your knee back down with control.
- Resistance: Place a resistance band just above the knees for added difficulty. Perform 15-20 reps per side.
Muscles Worked
- Primary movers: Gluteus medius, gluteus minimus
- Secondary: Hip external rotators (piriformis, obturator)
- Stabilizers: Core (obliques)
Common Mistakes
- Rolling the hips backward: Keep your hips stacked vertically. If you roll back, you lose glute medius isolation.
- Using the lower back: The rotation happens at the hip joint, not the spine.
Benefits
Clam shells isolate the glute medius, which is the primary stabiliser of the knee during single-leg movements. Strong glute medius prevents the knee caving that causes pain and injury during running, squats, and lunges.
HYROX® Context
Glute medius activation supports Sandbag Lunges (knee stability under load), running (pelvis stability in the gait cycle), and all squat movements (knee tracking). Programme 2 sets of 15-20 reps per side as part of every lower-body warm-up.
Variations & Alternatives
- Banded Lateral Walk - Standing glute medius activation with more functional demand.
- Bodyweight Bulgarian Split Squat - Single-leg strength building.
- Air Squat - Bilateral squat with banded abduction for knee tracking.
FAQ
How often should I do clam shells? Daily or before every lower-body session. They are low-fatigue and high-benefit.
Band or no band? Start without a band to learn the activation pattern. Add a band once you can feel the glute medius working.
Train smarter for your next HYROX® race with ROXBASE - the all-in-one training hub built for hybrid athletes. Explore programmes, exercises, and race strategy at roxbase.app.
Was this helpful?