This Stretch is the Most Underrated Forward Bend in Yoga

"As in any forward bend, the student must pay particular attention to the alignment of the vertebral column when practicing this pose. As much as possible the column-including the cervical (neck), thoracic (mid-back), and lumbar (lower) portions of the spine-should retain its natural or resting shape. When this pose is attempted, the pelvis must move over the heads of the femurs (thigh bones) at the hip joint."

"The pelvis is then tipped forward to the take strain out of the spinal column, especially the lumbar spine, which is especially mobile in flexion and extension (forward and backward bending). When the pelvis is tipped forward, the spinal column comes into a position relative so the pelvis is very similar to an erect sitting posture. The column is therefore not tipped in any direction."

Krounchasana (Heron Pose) differs from most forward bends because the leg is lifted against gravity rather than the trunk dropping toward the legs. Proper practice demands careful alignment of the vertebral column, preserving the cervical, thoracic, and lumbar natural shapes. The pelvis must move over the femoral heads and tip forward to remove strain from the spinal column, particularly the lumbar region. Correct pelvic tipping places the spine in a position akin to an erect seated posture, minimizing physiological strain and supporting mental calm. Adequate hamstring length and relaxation are essential for performing the pose safely.

Read at Yoga Journal