The Supine Pelvic Tilt Exercise demonstrates the posterior pelvic tilt, which helps to strengthen the muscles in your lower abdominal spine and stabilise your lower back.

Supine Pelvic Tilts
Step 1
Starting Position: Lie on your back with your knees bent and both feet flat on floor. Your arms are out to your sides in a “T” position palms facing up.
Step 2
Downward Phase: Exhale. Using your abdominal muscles, press your low back into the floor. Do not lift your hips or let your tailbone roll up off the floor. Hold this position briefly.
Step 3
Upward Phase: Inhale. Tip your pelvis in the opposite direction creating an arch in your low back/increasing the space between the low back and the mat. Do not lift your hips or let your tailbone roll up off the floor Hold this position briefly before returning to your starting position.

Source: AceFitting