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Begin by laying on your stomach on the exercise ball. Anchor your feet against a wall or BOSU or similar item. Hold the medicine ball to your chest with both hands.Using the muscles of the lower back, slowly straighten your upper body so that it is in a straight line with your legs. Hold for a few seconds and return to the starting position. Repeat this exercise 15-20 times. Be sure to do this exercise slowly so that you are giving your back muscles a proper workout, rather than just using the momentum from bouncing off the exercise ball.
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