Core-strength exercises strengthen your core muscles, including your abdominal muscles, back muscles and the muscles around the pelvis. You can do many core-strength exercises with a fitness ball.
In general, use a fitness ball sized so that your knees are at a right angle when you sit on the ball with your feet flat on the floor. Do each core-strength exercise five times. As you get stronger, gradually increase to 12 to 15 repetitions.
Breathe freely and deeply and focus on tightening your abs during each core-strength exercise. If you have back problems, osteoporosis or any other health concern, talk to your doctor before doing these core-strength exercises.