Dr. Wayne Westcott gives advice on strengthening your lower back.

Eight of 10 Americans have lower back pain, but conditioning your abdomen and lower back can help.


If you want to strengthen your midsection but don't have gym equipment at home, two of the best exercises you can do are trunk curls and trunk extensions.


Floor trunk curl


The trunk curl isolates your abdominal muscles. Here is the best way to do it: Lie face-up on the floor with your knees bent about 120 degrees, your feet on the floor and your hands lightly clasped behind your head to keep your neck in a neutral (straight) position.


Assuming you have a normal back arch, your upper back should touch the floor. Your lower back should not. Curl your upper back off the floor slowly while pressing your lower back into the floor by contracting your abdominal muscles. When your upper back and shoulders are a few inches above the floor, pause for a moment, then return slowly to the starting position.


If you do 20 of these the right way, you've performed a good midsection workout.


Although the floor-lying trunk curl is a highly effective abdominal strengthening exercise, it works the muscles through only half their full movement range. To enhance the training effect, perform this same exercise on a Swiss ball.


Swiss ball trunk curl


Lie face-up on the Swiss ball so that your lower back is atop the ball and your upper back is draped over the side. Your feet should be on the floor, and your torso should arch over the ball so that you feel a gentle stretch in your abdominal muscles.


Clasp your hands loosely behind your head to make sure your neck stays straight throughout. Curl your upper back off the ball slowly until your abdominal muscles are fully contracted. Pause momentarily, then return slowly to the starting position.


This full-range trunk curl will be harder and better for strengthening your midsection muscles. When you can complete 20 good Swiss ball trunk curls, you are doing very well. A good trunk curl takes four seconds for each repetition -- two seconds for the upward movement and two seconds for the downward movement.


Floor trunk extension


The trunk extension isolates your lower-back muscles, easily the most important in the body for muscular-skeletal fitness and prevention of injury.


Lie face-down on the floor with your hands lightly clasped under your chin to keep your neck straight. Your feet, legs and hips should touch the floor throughout. Lift your chest off the floor slowly while pressing your midsection into the floor by contracting your lower back muscles.


Pause for a moment -- your upper chest and shoulders should be a few inches above the floor -- then return slowly to the starting position. Ten properly performed trunk extensions is a good lower-back workout.


To enhance the training effect, perform this same exercise on a Swiss ball.


Swiss ball trunk extension


Lie face-down on the Swiss ball so that your midsection is on top of the ball with your chest draped over the side. Your feet should be on the floor and your torso should arch over the ball so that you feel a gentle stretch in your lower back muscles. Clasp your hands loosely under your chin to keep your neck straight throughout. Lift your chest off the ball slowly until your lower back muscles are fully contracted. Pause, then return slowly to the starting position with your chest touching the ball.


This full-range trunk extension will be harder and will provide a better lower-back workout. When you can complete 10 good Swiss ball trunk extensions, you are making excellent progress.


A good trunk extension takes four seconds for each repetition - two seconds for the upward movement and two seconds for the downward movement.


For best results, do at least one set of trunk curls and at least one set of trunk extensions three nonconsecutive days a week.


Wayne L. Westcott, Ph.D., is fitness research director at the South Shore YMCA in Quincy, and author of 10 fitness books.