The exercise ball lower back stretch (pyramid) is an exercise that targets the lats. To do this exercise, you will need an exercise ball and a mat. Start by lying on your back on the mat with your knees bent and your feet flat on the floor. Place the exercise ball under your lower back, just above your hips. Slowly roll the ball up your back until you are in a sitting position, with your arms extended overhead. Hold this position for a few seconds, then slowly roll back down to the starting position. Repeat this exercise for 10-12 repetitions.