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Knee folds

8 reps each side · beginner

Lying on the back with the head down, the knees bent and the feet flat, one leg lifts (folds in at the hip) into tabletop without the knee changing its angle much or the pelvis moving, then lowers until the foot is back on the mat. The simplest test of a still pelvis.

-24°Ankle dorsiflexion
125°Knee flexion
59°Hip flexion
90°Trunk from vertical
29°Arm to trunk
53°Elbow flexion
17Ankle spacing, cm
60Hand spacing, cm
0Knee outside ankle, cm
–Knee cave, ° inside toe line
–Load left / right, %
0Pelvis drop, cm

Load and joint demand

Bodyweight: no weights. Joint demand below is your own body's weight in this position.

Shoulder, per side
11 / 11

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

Abs and core
29 pts

Effort and your quota

1.5/10 effort1.5fatigue per set

8 slow, controlled reps on each side. Pilates is practised for control, balance and mobility, never to failure, so this does not change with your limits.

Level: beginner. One round counts like light conditioning work: 29 core points.

Prime movers

Transversus abdominis (holding the pelvis still), hip flexors (iliopsoas), rectus abdominis, obliques.

What to look for

  • Breathe out and float the leg up; the pelvis does not tip or rock.
  • Keep the weight even on both sides of the pelvis.
  • Place the foot back down quietly.
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.