Janu Sirsasana
hold 45 s each side · beginner · move in slowly, hold, come out the same way
Take care: Support the bent knee with a block if it doesn’t rest on the mat; bend the straight knee a little with tight hamstrings.
Janu Sirsasana with a strap: the left leg straight ahead with the foot flexed, the right knee bent out to the side and the right sole against the inner left thigh. A strap round the left foot is held in both hands; the chest turns a little toward the straight leg and folds forward over it.
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: 25 legs points, 9 core points.
Hamstrings and calf of the straight leg (stretched), spinal erectors and quadratus lumborum (stretched), adductors of the bent leg (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.