UTTANASANA Standing Forward Bend
From standing, with your feet hip-distance apart, hinge forward from your hip joints, keeping a long spine. Notice how muscles on the back body, especially the hamstrings in the back of your thighs, are controlling the creation of hip flexion, not the hip flexors. The hamstrings are working with the force of gravity to let you down gradually.
Hip flexion with gravity, created by a lengthening contraction of the hip extensors.