Lower, eccentric
Side view
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Dumbbell skull crusher

Lying on a flat bench with 12 kg dumbbells in a neutral grip; the elbows flex from straight to about 125° so the dumbbells lower beside the head.

-15°Ankle dorsiflexion
79°Knee flexion
39°Hip flexion
87°Trunk from vertical
100°Arm to trunk
5°Elbow flexion
60Ankle spacing, cm
52Hand spacing, cm
6Knee outside ankle, cm
–Knee cave, ° inside toe line
–Load left / right, %
0Pelvis drop, cm

Load and joint demand

Load in the model: 12 kg each hand. Balance and joint demand re-solve as you change it.

Shoulder, per side
18 / 49
Elbow, per side
10 / 43

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

Triceps
100 pts

Effort and your quota

1.5/10 effort1.6fatigue per set

Your quota per set: 10 reps at 12 kg each hand, stopping 2 reps short of failure.

One hard set earns 100 push points, 100 arms points.

Prime movers

Triceps brachii.

What to look for

  • Upper arms stay still, angled slightly back.
  • Neutral grip is easier on the elbows than a bar.
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.