Abdominal exercises.(Cover Story)

Treadmills and ellipticals are designed mainly to strengthen the heart and cardiovascular system, but other muscles need attention, too. Strong abdominal muscles can not only help improve your looks in a bathing suit, they can also prevent or ease low-back pain by helping back muscles support the torso. Building up your abs won't get rid of fat--that's possible only with the kind of aerobic exercise you might do on a treadmill or elliptical exerciser--but it does build muscle, which helps pull abdominal flab inward.

Before you retreat to the kitchen for a denial doughnut, note that the American College of Sports Medicine guidelines for strength-training exercise are fairly modest: a regular program of at least one set of 8 to 12 repetitions, two to three times a week, at a resistance that works the muscles to near fatigue. When you can do more than 12 reps, step up the resistance until about 8 reps feels challenging. Exercising your abs more than three times a week using external resistance, as you would with a machine or weights, could overwork the muscles, reducing gains and increasing the risk of injury.

Infomercials would have you believe that "washboard abs" are available only through an array of gadgets, from rockers and rollers to sliding tracks. Not so. Three exercises involving infomercial devices plus 10 other abdominal exercises were put to the test in a May 2001 study sponsored by the American Council on Exercise (ACE), a California-based group that promotes exercise and certifies fitness professionals. Researchers ranked the exercises according to how much muscle activity each produced in the abdominal muscles of 30 adult volunteers.

The results were gratifying to anyone who is hesitant to fork over $150 or so for an ab machine. The fancy equipment--the Torso Track, Ab Roller, and Ab Rocker, all still being sold--proved no more beneficial than some exercises that need no equipment. The bicycle maneuver was a top option, as was the crunch.

For advanced crunches, you can use one of the distinctly low-tech pieces of equipment ubiquitous in gyms--an exercise, or stability, ball, which also ranked high in the ACE study. These balls, made of vinyl that can be smooth or textured, were used for exercise as long ago as the early 20th century.

Peter Francis, director of the biomechanics lab at San Diego State University, is a ball advocate. "It's a legitimate physical-therapy tool," he says. "The exercise ball came from the Swiss physical-therapy community; it's not something someone invented in their garage three weeks ago. It's very versatile."

Exercise balls come in various sizes and shapes. Although many are round, some are oblong, and some have "legs" to keep them from rolling when ...