Jump and catchCentre of mass inside base of support
Side view
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Muscle snatch

A 30 kg bar on a snatch grip from the hips straight to locked out overhead with no dip under it: a short hinge and extension start it, then the elbows go high and the hands turn round under the bar while the legs stay straight.

3°Ankle dorsiflexion
2°Knee flexion
5°Hip flexion
1°Trunk from vertical
34°Arm to trunk
2°Elbow flexion
32Ankle spacing, cm
110Hand spacing, cm
-4Knee 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
11 / 125
Hip extensors
6 / 76
Knee flexors
15 / 17
Calves
32 / 32
Shoulder, per side
60 / 65
Elbow, per side
28 / 49

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

Shoulders
100 pts
Upper back
82 pts
Triceps
46 pts
Glutes
35 pts

Effort and your quota

4/10 effort4.2fatigue per set

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

One hard set earns 35 legs points, 146 push points, 82 pull points, 46 arms points.

Prime movers

Deltoids, trapezius, upper back, triceps, gluteus maximus.

What to look for

  • Legs straight once the bar passes the hips.
  • Elbows high and out, then turn the hands over.
  • Press out to lockout over the back of the neck.
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.