Lower
Side view
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Single-leg back extension

45° back extension with only the right foot anchored; the left leg hangs bent. The single anchor makes the working hip do more.

0°Ankle dorsiflexion
3°Knee flexion
2°Hip flexion
45°Trunk from vertical
55°Arm to trunk
143°Elbow flexion
20Ankle spacing, cm
12Hand spacing, cm
-2Knee outside ankle, cm
–Knee cave, ° inside toe line
–Load left / right, %
0Pelvis drop, cm

Load and joint demand

Bodyweight exercise: the load slider has no effect here; body mass comes from your limits.

No gravity-based joint demand to show for this exercise.

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

Hamstrings
100 pts
Glutes
100 pts
Lower back
82 pts

Effort and your quota

7/10 effort7fatigue per set

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

One hard set earns 200 legs points, 82 core points.

Prime movers

Gluteus maximus and hamstrings of the anchored leg, spinal erectors.

What to look for

  • Squeeze the working glute to come up.
  • Keep the pelvis level.
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.