The supine alternate bent knee fall out exercise is designed to strengthen and improve recruitment of the lower abdominal muscles, which provide support for your low back.
Begin lying on a mat with your knees bent and feet flat on the floor. You may place your fingers on your hip bones to monitor your pelvis.
Tighten your lower abdominal muscles and lower one knee down toward the mat as far as you can without allowing your pelvis to rotate. Bring your knee back up to the starting position. Repeat on the other side.