Display

Look for a clear display with easy-to-use controls. A good one will show some combination of your heart rate, calories burned, speed, and resistance levels, and details such as time and distance.

Programming

Look for machines with programs that allow you to adjust routines based on your fitness level and have heart-rate-controlled workouts that consider your age, weight, and gender.

Heart-rate monitor

Those with a chest strap are best; they don't impede your movement. Contact monitors measure your heart rate only when you're touching them, which can be inconvenient. Stand-alone heart-rate monitors are available for about $28 to $100. (See heart-rate monitor Ratings, available to subscribers.)

Resistance

Look for a machine that is easy to adjust and has a variety of workout levels. Treadmills offer a range of speeds and inclines. Some can simulate running or walking downhill.

Features

Decide which extra features are important to you. There are treadmills with an LCD TV or adjustable deck cushioning. But many panelists found drawbacks with other models in the lack of simple niceties, such as a book rest or a place for your water bottle.