Crunch
Side view
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Cable crunch

Kneeling below a high pulley, rope held at the head. The trunk flexes from about 15° to 70° forward while the hips stay still. Cable force is not modelled.

-75°Ankle dorsiflexion
90°Knee flexion
12°Hip flexion
15°Trunk from vertical
124°Arm to trunk
133°Elbow flexion
17Ankle spacing, cm
16Hand spacing, cm
0Knee outside ankle, cm
–Knee cave, ° inside toe line
–Load left / right, %
0Pelvis drop, cm

Load and joint demand

Machine or cable load (40 kg at this setting) is not modelled, so joint demand shows the body only.

No gravity-based joint demand to show for this exercise.

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

1.5/10 effort1.6fatigue per set

Your quota per set: 10 reps at 40 kg, stopping 2 reps short of failure.

One hard set earns 100 core points.

Prime movers

Rectus abdominis, obliques.

What to look for

  • Hips stay put; the ribs curl toward the pelvis.
  • Hands stay fixed by the head.
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.