Descent, eccentricBalanced over midfoot, bar 0.1 cm behind
Side view
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Back squat

High-bar, 100 kg, feet a little wider than hips with 20° toe-out. Knee and hip follow a depth profile to just below parallel; trunk lean is solved so lifter plus bar balance over midfoot.

2°Ankle dorsiflexion
2°Knee flexion
9°Hip flexion
6°Trunk from vertical
35°Arm to trunk
138°Elbow flexion
42Ankle spacing, cm
84Hand spacing, cm
-6Knee outside ankle, cm
–Knee cave, ° inside toe line
50 / 50Load left / right, %
0Pelvis drop, cm

Load and joint demand

Load in the model: 100 kg. Balance and joint demand re-solve as you change it.

Lower back
11 / 400
Hip extensors
11 / 237
Knee extensors
29 / 113
Calves
62 / 62

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

Quads
100 pts
Glutes
82 pts
Adductors
64 pts
Lower back
46 pts

Effort and your quota

9/10 effort9.4fatigue per set

Your quota per set: 10 reps at 100 kg, stopping 2 reps short of failure.

One hard set earns 246 legs points, 46 core points.

Prime movers

Quadriceps, gluteus maximus, adductor magnus, spinal erectors.

What to look for

  • Bar path stays close to vertical over the foot.
  • Knees track in line with the toes; turn up knee cave and use the front camera to see the fault.
  • Longer femurs force more forward lean; try the femur slider.
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.