There are typically two price ranges for treadmills--$1,000 and below, and $2,000 and up. There are few models between those two price points. In our tests, we focus on the less expensive, and more prevalently purchased, group.

One of the biggest complaints from CR subscribers about treadmills has to do with their durability. In the past, we've found treadmills to be very trouble-prone. The newer models seem to be improving in this area, but our durability test is a good way to uncover potential problems. We evaluate the durability of a model's motor, deck, belt, front and rear rollers, bearings, and the circuitry that drives the machine.

To test durability, we employ a device created in our labs and affectionately dubbed "Johnny Walker" (below left). It has eight "feet" mounted to an eight-sided aluminum drum supported by an A-frame on each side. Load cells are mounted at each end of the drum so we can simulate the weight of a 200-pound person. The treadmills are placed under the Johnny Walker and run at 6 mph. They're cycled for one hour on, and a half-hour off, to allow the treadmill to cool. Each model is tested for a total of 50 hours.