Step and dropCentre of mass inside base of support
Side view
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Kettlebell forward lunge

A step forward of about 80 cm into a lunge with a 16 kg bell hanging in each hand, then a push back to standing.

4°Ankle dorsiflexion
5°Knee flexion
3°Hip flexion
2°Trunk from vertical
5°Arm to trunk
0°Elbow flexion
20Ankle spacing, cm
44Hand spacing, cm
-1Knee outside ankle, cm
–Knee cave, ° inside toe line
50 / 50Load left / right, %
0Pelvis drop, cm

Load and joint demand

Load in the model: 16 kg each hand. Balance and joint demand re-solve as you change it.

Lower back
18 / 48
Hip extensors
10 / 28
Knee extensors
8 / 109
Calves
26 / 328

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
Forearms and grip
46 pts

Effort and your quota

7/10 effort7.3fatigue per set

Your quota per set: 10 reps at 16 kg each hand, stopping 2 reps short of failure.

One hard set earns 246 legs points, 23 arms points.

Prime movers

Quadriceps, gluteus maximus, adductors, grip.

What to look for

  • Land heel first, then sink straight down.
  • Push back hard off the front foot.
  • Bells hang still at the sides.
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.