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Clamshell

Lying on the right side with hips at 45° and knees at 90°, feet together. The top knee opens by rotating the thigh out while the feet stay touching. Built upright and rotated onto its side.

-10°Ankle dorsiflexion
90°Knee flexion
45°Hip flexion
90°Trunk from vertical
158°Arm to trunk
120°Elbow flexion
0Ankle spacing, cm
80Hand spacing, cm
-31Knee outside ankle, cm
–Knee cave, ° inside toe line
–Load left / right, %
-17Pelvis drop, cm

Load and joint demand

Bodyweight exercise: the load slider has no effect here; body mass comes from your limits.

Shoulder, per side
11 / 11

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

Effort and your quota

3.5/10 effort3.5fatigue per set

Your quota per set: 23 reps at bodyweight, stopping 2 reps short of failure.

One hard set earns 35 legs points.

Prime movers

Gluteus medius and minimus, deep hip external rotators.

What to look for

  • Feet stay together; the pelvis does not roll back.
  • Small, controlled range.
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.