Posterior pelvic tilt on the floor

Lie on the floor on your back with your entire body extended.

Contract your abdominals, hamstrings, and glutes simultaneously to rotate your hips backwards, eliminating the lumbar curvature and allowing the lower part of your back to touch the ground.

When you return to the starting position, exaggerate the opposite movement, maximizing your lumbar curvature so that you can feel the difference between the two positions.

Try to keep your hands off the ground to work on your shoulder mobility.