To relieve tension in your lower back, tighten your butt (gluteus) muscles and, at the same time, tighten your abdominal muscles to flatten your lower back. Hold this tension for 5-8 seconds, then relax. Repeat 2-3 times. Concentrate on maintaining constant muscle contraction. This pelvic tilting exercise will strengthen the butt (gluteus) and abdominal muscles so that you are able to sit and stand with good posture.