Arc back
Side view
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Arm arcs

8 reps · beginner

Lying on the back with the knees bent and the feet flat, the straight arms reach up to the ceiling over the shoulders. Breathing in, both arms arc back overhead toward the mat as far as the ribs stay down; breathing out, they return over the shoulders.

-23°Ankle dorsiflexion
125°Knee flexion
59°Hip flexion
90°Trunk from vertical
90°Arm to trunk
3°Elbow flexion
18Ankle spacing, cm
46Hand spacing, cm
4Knee 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
1 / 12

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

Lats
35 pts
Triceps
35 pts
Shoulders
29 pts
Abs and core
8 pts

Effort and your quota

4.5/10 effort4.5fatigue per set

8 slow, controlled reps. 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: 64 push points, 35 pull points, 35 arms points, 8 core points.

Prime movers

Latissimus dorsi and triceps (lengthening), anterior deltoid, serratus anterior, transversus abdominis and obliques (keeping the ribs down).

What to look for

  • Let the arms go back only as far as the back ribs stay heavy on the mat.
  • Keep the shoulder blades settled; the neck stays long.
  • Breathe in as the arms go back, out as they return.
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.