When buying a treadmill, here are some things to keep in mind:

Treadmill Motor: The continuous-duty rating is the motor's true continuous horsepower, not just it's
"peak" horsepower. So a 2.0 continuous-duty HP motor is actually more powerful than a 2.0 HP
motor not rated as continuous duty. For good wear, Look for a motor with at least 1.5
continuous-duty HP. Most treadmills are AC, which tend to
be noisy and require a dedicated power line.

Treadmill Speed: Most treadmills run from 0 to 10 mph. A safe starting speed is always an important
safety feature. Treadmills designed for more serious jogging or running go up to 12mph.
Some offer one-touch speed buttons to adjust speed quickly and easily.

Treadmill Belt and Deck: Be sure the length of the treadbelt is long enough for your longest stride.
The width of the belt should be at least 16", although wider belts allow for more comfortable strides.
Likewise, longer decks allow for a more comfortable stride. Two-ply belts are stronger
and less likely to curl at the sides. Quality decks shouldn't need much maintenance and operate
at low temperatures.

Impact Absorption: Treadmills usually absorb some of the force from the impact of your feet.
Some use cushioning under the belt, others have cushioning in the belt itself. Some even offer
electronic adjustable cushioning. The lower the impact, the better.

Incline: The incline can range from 0% to about 15%. A wider range is the best choice. The most
high-tech treadmills offer incline that adjusts according to the exerciser's heart rate.
Others have automatic electronic incline with the push of a button. The electronic incline
should not be noisy or cause trembling. The least favorable are those that require manual
adjustment before starting your workout.

Control Panels: Electronic feedback displays of speed, time, and distance are generally
standard on most treadmills. Some also display calories burned, heart rate, incline or
workout history. Most treadmills offer preset and/or custom programs you can design yourself.
Control panels range from a simple display to fully programmable consoles with high-tech features,
such as the ability to run programs from the Internet. Price is influenced by the control
panel options, so purchase only what you will regularly use.

Heart Rate Monitors: Many treadmills include some type of electronic heart-rate monitor that
enables the user to stay in his target heart rate without having to stop and manually take a pulse.
Chest-strap monitors tend to be the most accurate. Thumb pulse, ear clip and other strap methods
are also available, but less precise.

Treadmill Frame: High alloy, welded steel with a protective coating to avoid rust is the way to go.
Avoid weaker materials and bolted frames.

Hand Rails: Some treadmills are designed with a handlebar in front, some with side rails.
The location is a matter of preference.

Treadmill Warranty: Look for a a multi-year motor warranty and one or more years of included service.
The motor and labor may also be under a limited warranty.

Treadmill Price: For a good quality motorized treadmill, expect to pay $1,000 or more. Home treadmills
with the most advanced features and electronics will run up to $2,500 or more.

Article Source: *Journal of the American Medical Association; May 8, 1996;
Energy Expenditure with Indoor Exercise Machines; Anne I. Zoni, DO;
Martin D. Hoffman, MD; Philip S. Slifford, PhD. Also reported in USA Today.