Slide show: Core-strength exercises with a fitness ball

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 10 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.

To do a squat and reach exercise with the fitness ball:

• Hold the ball in front of you and bend your knees. Keep your back straight and your arms parallel to the floor (A). Don't let your knees extend beyond your feet.
• Tighten your abdominal muscles.
• Rotate your trunk and reach with the ball toward your left (B). Hold for three deep breaths.
• Return to the start position and repeat to the right.
• Vary the exercise by holding the ball in a downward position (C) or an upward position (D).

To do abdominal crunches with the fitness ball:

• Sit on the ball with your feet resting on the floor, about hip-width apart. Keep your back straight. Cross your arms on your chest.
• Tighten your abdominal muscles.
• Lean back, as shown, until you feel the muscles in your midsection tighten. Hold for three deep breaths.
• Return to the start position and repeat.

To work various core muscles in combination for better core strength, try a bridge with the fitness ball:

• Lie on your back with your legs resting on top of the ball.
• Tighten your abdominal muscles.
• Raise your hips and buttocks off the floor into a bridge (A). Hold for three deep breaths. This works your core muscles and the muscles along your backside — the gluteal muscles and hamstrings — as they contract to keep you in place.
• Return to the start position and repeat.
• For added challenge, raise your right leg off the ball (B). Repeat with your left leg.

When you're comfortable doing the bridge with the fitness ball, add a heel dig for more core strength:

• Lie on your back with your legs resting on top of the ball. Raise your hips and buttocks off the floor into a bridge (A).
• Tighten your abdominal muscles.
• Keep your hips off the floor while you pull the ball closer to your buttocks with your feet (B). Dig your heels into the ball for traction and to engage the muscles along the back of your thighs (hamstrings). Hold for three deep breaths.
• Return to the start position and repeat.

The plank is a classic core-strength exercise with the fitness ball:

• Lie on the ball on your stomach, with your feet touching the floor behind the ball. Lean forward until you touch the floor with your hands.
• Walk your hands away from the ball until you feel the ball reach your upper thighs, as shown. Keep your feet suspended above the floor while you balance on your hands and on the ball. Keep your shoulders directly above your hands.
• Tighten your abdominal muscles. Hold for three deep breaths or as long as you can maintain your balance and form.
• Return to the start position and repeat.

When you're comfortable doing the plank with the fitness ball, add the advanced plank for even more core strength:

• Lie on the ball on your stomach, with your feet touching the floor behind the ball. Lean forward until you touch the floor with your hands.
• Walk your hands away from the ball until you feel the ball reach your upper thighs (A). Keep your shoulders directly above your hands.
• Tighten your abdominal muscles.
• Push your body weight forward until your shoulders are in front of your hands and the ball is beneath your shins (B). Hold for three deep breaths.
• Return to the start position and repeat.

To do the abdominal ball raise exercise with the fitness ball:

• Lie on your back and rest your legs on top of the ball with your legs about hip-width apart. Tighten your abdominal muscles and squeeze your legs together.
• Raise the ball off the floor, as shown. To protect your lower back, focus on pulling your bellybutton in toward your spine and keeping your abdominal muscles contracted. Hold for three deep breaths.
• Return to the start position and repeat.
• For added challenge, raise the ball off the floor and let your legs slowly fall to the right. Stop before you reach the floor. Hold for three deep breaths, keeping your shoulders on the floor. Return to the start position and repeat on the left side.

To do the side exercise with the fitness ball:

• Lie on your right side, with the ball between your legs. Support yourself with your arm along the floor.
• Tighten your abdominal muscles.
• Keeping the ball between your legs, raise your legs off the floor, as shown. Hold for three deep breaths.
• Return to the start position and repeat. Also try the exercise lying on your left side.

To try an advanced core exercise, do the reverse crunch with the fitness ball:

• Lie on the ball on your stomach, with your feet touching the floor behind the ball. Lean forward until you touch the floor with your hands. Walk your hands away from the ball until you feel the ball reach your upper thighs. Keep your shoulders directly above your hands.
• Tighten your abdominal muscles.
• Press your knees into the ball, as shown. Then use your abdominal muscles to bring your knees toward your chest. Hold for three deep breaths.
• Return to the start position and repeat.