Curl, concentricBalanced over midfoot, bar 5.4 cm ahead
Side view
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Barbell curl

30 kg straight bar, shoulder-width underhand grip. Upper arms stay close to vertical while the elbows flex from 10° to 140°; whole-body lean is solved.

3°Ankle dorsiflexion
2°Knee flexion
4°Hip flexion
3°Trunk from vertical
4°Arm to trunk
10°Elbow flexion
28Ankle spacing, cm
43Hand spacing, cm
-3Knee outside ankle, cm
–Knee cave, ° inside toe line
50 / 50Load left / right, %
0Pelvis drop, cm

Load and joint demand

Load in the model: 30 kg. Balance and joint demand re-solve as you change it.

Lower back
34 / 114
Hip extensors
19 / 56
Knee flexors
25 / 45
Calves
40 / 40
Shoulder, per side
10 / 62
Elbow, per side
9 / 52

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

Biceps
100 pts
Forearms and grip
64 pts

Effort and your quota

1.5/10 effort1.6fatigue per set

Your quota per set: 10 reps at 30 kg, stopping 2 reps short of failure.

One hard set earns 60 pull points, 132 arms points.

Prime movers

Biceps brachii, brachialis, brachioradialis.

What to look for

  • Elbows stay at the sides.
  • A small counter-lean is physics; a swing is cheating.
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.