Step and dropCentre of mass inside base of support
Side view
Drag to orbit, pinch or scroll to zoom

Forward lunge

Starts standing, steps forward about 80 cm, drops into the split and pushes back. Front foot is in the air for part of the step, so balance is checked against whichever feet are down.

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: 12 kg each hand. Balance and joint demand re-solve as you change it.

Lower back
16 / 42
Hip extensors
9 / 25
Knee extensors
7 / 101
Calves
24 / 304

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
Calves and shins
46 pts

Effort and your quota

7.5/10 effort7.8fatigue per set

Your quota per set: 10 reps at 12 kg each hand, stopping 2 reps short of failure.

One hard set earns 278 legs points.

Prime movers

Quadriceps, gluteus maximus, adductors; calves and hips decelerate the step.

What to look for

  • Watch the base of support shrink to one foot during the step.
  • Front shin ends near vertical; the push back comes from the front heel.
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.