Take care: Take care: the lower back holds the load with no help from the legs. Keep it light and skip it with a lower-back injury.
Sitting astride a bench with the feet wide and 40 kg on the back; the trunk hinges forward from upright to about 60° and back. The legs are taken out, so the hips and back do all the work.
Load in the model: 40 kg. Balance and joint demand re-solve as you change it.
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.
Femur changes keep standing height fixed by shortening or lengthening the torso. Longer femurs force more forward lean in any squat.
Your quota per set: 10 reps at 40 kg, stopping 2 reps short of failure.
One hard set earns 192 legs points, 100 core points.
Spinal erectors, gluteus maximus, hamstrings, adductors.
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.