Curl, concentricBalanced over midfoot, bar 5.4 cm ahead
Side view
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Barbell 21s

Seven curls from the bottom to halfway, seven from halfway to the top, then seven full curls, without rest. The demonstration shows the half reps and full reps in turn; same grip and joint path as the barbell curl.

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 / 61
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

  • Seven bottom halves, seven top halves, seven full reps.
  • Use about two-thirds of your usual curl weight.
  • Elbows stay at the sides the whole set.
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.