Descent, eccentricBalanced over midfoot
Side view
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Sandbag bear-hug squat

A 30 kg sandbag hugged high against the chest, arms wrapped round it, squatting to below parallel and standing up.

0°Ankle dorsiflexion
2°Knee flexion
18°Hip flexion
10°Trunk from vertical
64°Arm to trunk
111°Elbow flexion
54Ankle spacing, cm
15Hand spacing, cm
-9Knee 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
24 / 220
Hip extensors
6 / 128
Knee extensors
17 / 64
Calves
36 / 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

Quads
100 pts
Glutes
82 pts
Abs and core
35 pts
Upper back
32 pts
Biceps
23 pts

Effort and your quota

7/10 effort7.3fatigue per set

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

One hard set earns 182 legs points, 46 pull points, 23 arms points, 35 core points.

Prime movers

Quadriceps, gluteus maximus, upper back (holding), biceps (holding), abdominals.

What to look for

  • Hug the bag tight and high; elbows down.
  • Sit between the heels with the chest up.
  • Drive up through the whole foot.
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.