Curl, concentric
Side view
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Spider curl

Face down on a 45° incline bench, arms hanging straight down over the top edge; the curl works from a shortened shoulder position.

44°Ankle dorsiflexion
75°Knee flexion
36°Hip flexion
45°Trunk from vertical
45°Arm to trunk
10°Elbow flexion
28Ankle spacing, cm
38Hand spacing, cm
-4Knee outside ankle, cm
–Knee cave, ° inside toe line
–Load left / right, %
0Pelvis drop, cm

Load and joint demand

Load in the model: 10 kg each hand. Balance and joint demand re-solve as you change it.

Shoulder, per side
6 / 36
Elbow, per side
6 / 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

Biceps
100 pts

Effort and your quota

1/10 effort1fatigue per set

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

One hard set earns 60 pull points, 100 arms points.

Prime movers

Biceps brachii (short head), brachialis.

What to look for

  • Arms hang vertically, not swinging.
  • Peak contraction is the hard part here.
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.