Move the legs apart. Sit down and bend both knees. Open both legs simultaneously in slow motion and bring them back together. Upper body always remains low until the repetitions are finished.
Pelvic bones should always be parallel to the handrail.
Avoid raising upper body.
For a bigger body tension challenge: hold a medicine ball or an elastic band in front of or above your head.
An advanced version is the LUNGE TWIST, where turntables are attached to the treads.