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Banded clamshell

12 reps each side · beginner

Lying on the right side, head on the outstretched bottom arm and the top hand on the mat in front of the chest, hips bent about 45° and knees about 90° with the feet in line with the back, a resistance band looped round both thighs just above the knees. Keeping the feet together, the top knee opens up against the band as far as the pelvis stays still, then closes.

-15°Ankle dorsiflexion
90°Knee flexion
45°Hip flexion
80°Trunk from vertical
171°Arm to trunk
0°Elbow flexion
0Ankle spacing, cm
27Hand spacing, cm
31Knee outside ankle, cm
–Knee cave, ° inside toe line
–Load left / right, %
-17Pelvis drop, cm

Load and joint demand

Bodyweight: no weights. Joint demand below is your own body's weight in this position.

Shoulder, per side
12 / 12

N·m now / peak over the rep.

Faults

Faults grow with knee bend and apply to lifts standing on the floor. The fault check flags a knee caving more than 10° inside the line of the toes and a load split beyond 60/40. Knee cave shows best in the front camera.

Body

Femur changes keep standing height fixed by shortening or lengthening the torso. Longer femurs force more forward lean in any squat.

Muscles worked

Glutes
35 pts
Abs and core
6 pts

Effort and your quota

3.5/10 effort3.5fatigue per set

12 slow, controlled reps on each side. Pilates is practised for control, balance and mobility, never to failure, so this does not change with your limits.

Level: beginner. One round counts like light conditioning work: 35 legs points, 6 core points.

Prime movers

Gluteus medius and minimus, deep hip external rotators (piriformis, obturators), gluteus maximus, obliques (keeping the pelvis still).

What to look for

  • Keep the heels touching; the knee opens like a shell.
  • Do not let the top hip roll back as the knee opens.
  • Open for one count, close for two against the band.
How the model works, and its limits

One 3D skeleton drives both views. Segment lengths and widths are Winter's anthropometric ratios of height; segment masses and centre-of-mass positions follow Dempster's data. For free-standing lifts the whole-body angle is found numerically so the combined centre of mass of lifter and load sits over the middle of the foot. Arms and legs use two-link inverse kinematics with a pole direction. Rep timing follows a minimum-jerk profile.

Balance is quasi-static, so ballistic lifts are shown slowed down. Cable pull and pad support forces are not modelled. The spine is one rigid segment and joints have no range-of-motion limits or muscle forces.