Supta Matsyendrasana
hold 45 s each side · beginner · move in slowly, hold, come out the same way
Take care: Twist gently; keep the knee higher (on a block) and skip it after recent back surgery or with a disc problem that twisting aggravates.
Supta Matsyendrasana: lying on the back with the arms out in a T, the right knee draws in to the chest and then crosses over to the left, the pelvis rolling about 70° so the right knee rests on the mat beside the left hip while the left leg stays long. The shoulders stay flat (the chest is turned back against the pelvis) and the head turns to the right.
Bodyweight: no weights. Joint demand below is your own body's weight in this position.
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.
Femur changes keep standing height fixed by shortening or lengthening the torso. Longer femurs force more forward lean in any squat.
Hold for 45 seconds on each side: move into the pose slowly, breathe steadily, and come out the way you went in. Yoga 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: 7 legs points, 5 push points, 19 core points.
Obliques (stretched), spinal erectors (stretched), gluteus medius and piriformis of the top leg (stretched), pectoralis major (stretched).
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.