Curl up
Side view
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Weighted crunch

Lying with the knees bent and the feet flat, a 10 kg dumbbell held across the chest. The trunk curls up to about 30° from the floor; the lower back stays down.

-32°Ankle dorsiflexion
110°Knee flexion
52°Hip flexion
90°Trunk from vertical
58°Arm to trunk
135°Elbow flexion
24Ankle spacing, cm
24Hand spacing, cm
2Knee outside ankle, cm
–Knee cave, ° inside toe line
–Load left / right, %
0Pelvis drop, cm

Load and joint demand

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

Shoulder, per side
22 / 30
Elbow, per side
35 / 36

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

Abs and core
100 pts

Effort and your quota

2/10 effort2fatigue per set

Your quota per set: 13 reps at bodyweight, stopping 2 reps short of failure.

One hard set earns 100 core points.

Prime movers

Rectus abdominis, obliques.

What to look for

  • Lift the shoulder blades; keep the lower back down.
  • Hold the dumbbell still on the chest.
  • Breathe out as you curl up.
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.