Treadmill. The top-ranked home aerobic equipment for years running is available with a wide array of features, from varying incline to feedback on time, distance, and calories burned.

Look for a wide, long, stable belt that can accommodate your stride and weight; emergency shutoff; and slow-start speeds; as well as quality in the drive train, belt, and deck. Cushioning features can help lessen the impact on feet and knees.

Stationary cycle. With a small learning curve, sta¬tionary cycles are easy to use, and low impact. Available in upright or recumbent styles, some cycles come with movable handles to work your upper body as you go, and you should make sure the one you buy has a comfortable, adjustable seat, interchangeable seat posts, and adjustable handles and toe straps. Less costly "trainers" allow you to convert your outdoor bicycle for indoor use.

Step machines. Whether stair-climbing or pedal-pushed, these can provide a good workout, though with a larger learning curve than tread¬mills and cycles.

Machines with independent steps require more coordination. Look for steps paral¬lel to the floor at all times, and a stable railing to grasp.

Elliptical trainers. The hot new category of machines—a cross between stair-climbing, crosscountry skiing, and jogging—which FPC’s Lynn Allen calls "fabulous" for the machines’ short learning curve, extremely low impact, and cardio¬vascular effectiveness.

"Some clubs have a thirty-minute limit on it and people wait their turn like vultures," she says. "You know it’s popular." Look for changeable elevation; feedback; smooth, elliptical motion; and a big, nonslip foot bed. Some models provide upper-body workouts, as well.