Data from the National Sporting Goods Association indicates that treadmills have been the number-one-ranked home aerobic equipment for the past three years.

If you've decided to join the ranks of treadmill owners, there are a number of factors to consider to ensure that you purchase a machine that meets your needs.

There are a multitude of treadmills on the market with prices ranging from $299 to $4,000. You are likely to find that a treadmill's cost directly reflects its quality.

Before you leave your home, measure the space in which you'd like to keep the treadmill. While the average treadmill measures 64 inches long and 28 inches wide, there are machines that fold up to be stored under a bed or in a closet.

Drive to the nearest fitness-equipment specialty store where the staff will be knowledgeable and you can choose from a wide variety of machines. Wear a comfortable pair of athletic shoes — the same pair you'll wear as you exercise on the machine at home.

Consider three key elements as you shop: construction, programming features and the warranty.

Construction

First, look at the treadmill's motor size (measured in horsepower) to determine the machine's longevity. Some manufacturers measure horsepower at continuous duty (the motor's ability to function under a load for an extended period of time), others at peak duty. Look for a motor with a minimum 2.0 continuous-duty horsepower, which will accommodate users who weigh more than 180 pounds.

Next, examine the treadmill's belt and deck. The belt should be at least two-ply, 17 inches wide and 49 inches long. The board thickness should measure at least an inch.

The deck acts as a cushion for the joints, legs, back and feet. The most sought-after treadmills feature low-impact decks that flex under the user’s foot plant to absorb the shock without rebounding to cause additional jarring. This feature is essential for individuals with shin splints and foot and back problems.

A sturdy frame supports the belt and deck system. Treadmills that cost between $399 and $1900 usually have a steel frame; treadmills with a price of $1900 or higher often are constructed with aircraft aluminum frames that offer additional flexibility for impact absorption. Aluminum frames don't rust or corrode and are lighter and easier to move.

Programming features

Lower-priced treadmills offer basic programming for variable speed, time, distance and calories. However, they seldom utilize user information, and the calorie counters aren't very accurate.

The quality of the programming features, such as preset programs that automatically vary the workout intensity by raising or lowering elevation and increasing or decreasing speed, rises with price. Heart-rate control programs are convenient features that consider the user's age and weight and keep the exerciser at an intensity sufficient to achieve maximum fat-burning or cardiovascular benefits.

Other programming options include incline/grade settings. A maximum grade of 10 percent may challenge beginning exercisers, while experienced exercisers may need a treadmill that reaches a 15-percent grade.

Warranty

Most manufacturers warranty against manufacturing defects only, not normal wear and tear, and if a user weighs more than the machine's specifications, a warranty may be voided. Many machines come with a lifetime warranty on the frame, while warranties on features and components usually range from 90 days to three years, depending on the machine's quality.

Higher-end machines often come with a one-year in-home labor contract. You can purchase renewable extended warranties that cover everything from parts to labor.

Don't give the man your money yet

Is the machine loud? Do you like how it looks? Does it offer a smooth ride? Is it easy to operate? Remember, this product will be around for a long, healthy time, so determine what you want and need from it before you begin shopping to prevent a regretful purchase.

Why treadmills are ranked #1

In 1996, the Journal of the American Medical Association reported that, based on a study from the Medical College of Wisconsin and Veterans Affairs Medical Center in Milwaukee, treadmills provide the most efficient way to burn calories when compared to other popular exercise machines.

Researchers asked eight male and five female young adults to exercise on six different types of indoor exercise machines, including a cross-country skiing simulator, cycle ergometer, rowing ergometer and stair stepper. They compared energy expenditure at ratings of perceived exertion (RPE) levels of 11 (fairly light), 13 (somewhat hard) and 15 (hard), and found that subjects who exercised at an RPE of 13 burned approximately 40 percent more calories per hour on the treadmill as compared to the cycle ergometer, which produced the lowest energy expenditure.