The benefit to working on your lower back or abs is that one reinforces the other. If you work on your back, you will strengthen your abs in the process. When you concentrate your movements and alternate between focusing on each muscle group, your balanced development of muscle groups has a better chance of maximum results. Be sure to hold each position for 8-10 seconds each with 3-4 reps. If you are beginning, start with 5 seconds and work your way up one second each day.
When using a large ball, arm placement additionally tightens the arms and helps combat those flabby or saggy spots that always tend to be problem areas. By incorporating the stabilizing or body resistant positioning of your arms while using the ball, you can additionally work on arm strength at the same time that you work on your lower back and abdominal muscles.
@idealprmedia The IDEAL Magazine: Fitness