What the best treadmill has
• A large treadmill belt. Experts recommend a treadmill belt that measures at least 20 by 60 inches. That leaves plenty of room for even tall, long-legged users to run without feeling cramped. Shorter belts -- found on cheaper folding motorized and manual treadmills -- are best suited for walking or jogging workouts. Very narrow belts can feel unsafe for some users.
• A powerful motor. For runners, look for a motor with a continuous-duty rating of at least 3 horsepower. Walkers and joggers can get away with a weaker motor, but it should still be rated for continuous duty as opposed to peak horsepower. The latter isn't a reliable indicator of a motor's long-term performance.
• Incline and decline settings to simulate real-world terrain. Only a few treadmills offer decline settings; but you can reasonably expect a maximum incline of 15 percent from any mid-range to high-end treadmill.
• A deck that's at least a three-quarters of an inch thick. A strong, thick deck is less likely to crack under heavy, prolonged use, and will provide cushioning for your joints.
• Responsive controls. Look for controls you can operate quickly and safely without breaking stride. "Quickset buttons" allow users to change settings like speed or incline with just the touch of a button -- no need to hold a button down or scroll through various settings.
• A large, easy-to-read display. You'll likely prefer one that shows all the information you need at once; some scan through workout metrics one at a time.
• A strong warranty on the motor, deck and frame. The best warranties offer lifetime coverage for those treadmill components. They also offer up to five years of coverage for parts and two years of labor coverage. Cheap treadmills, including manual treadmills, typically have shorter coverage -- one year, or even 90 days in some cases. That can be a pretty good indication of relative build quality -- or lack thereof.
Know before you go
Do you have enough space for a treadmill? Measure the space you have available, then check out each treadmill's size specifications -- not just the belt, but the total footprint of the machine. If you plan to walk or run at a steep incline, measure the vertical distance, too. Add your own height to make sure you have plenty of ceiling clearance. Non-folding treadmills are the sturdiest option, but a folding running deck can save valuable space in your home.
Can you handle installation and set up on your own? Some of the negative user reviews we spotted complain of assembly and set-up challenges with their treadmill. If you are not somewhat handy, buying a treadmill from a fitness store that can handle all of that for you might be a good idea. Keep in mind that a motorized treadmill can weigh a couple of hundred pounds -- and that many delivery companies will take the box only as far as your door, or in some cases the curb. If you're not sure you can handle a 200- to-300-pound box, consider paying extra for inside delivery, or again, buy from a retailer that will set up your treadmill for you.
How much do you weigh? Each treadmill has a maximum user weight limit. Make sure the heaviest person who will use the machine weighs no more than that limit, and, especially in the case of lower-end treadmills, leaving a healthy cushion is probably a good idea. If you're heavier than the treadmill's weight limit, you'll most likely void its warranty at best, and at worst risk the danger of serious injury should the treadmill structurally fail while in use.
Are you a walker or a runner? For those who plan to walk or, at most, jog, a lower-cost treadmill will usually suffice. However, running subjects a treadmill to much more stress. Look to a non-folding treadmill or a higher-quality folding model to ensure that your treadmill can take what a runner can dish out.
Consider the surface. Runners will often prefer a belt that's firm to simulate the feel of running on the road. However, a firm belt can be tougher on your joints. Most treadmills have a single comfort level, but others allow you to adjust cushioning from road hard to softer than running on grass, or have optional cushioning systems to accommodate different needs.
Are you committed to exercising regularly? A good treadmill can get expensive, and statistics show that far too many wind up as dust collectors or clothing trees. If you are just beginning an exercise regimen, buying an inexpensive treadmill as a starter machine might not be the worst idea. Ignore the fanciest, feature laden options and concentrate of finding a well put-together treadmill that will last long enough for you to be able to determine if you use it enough to graduate to a higher end machine.
Cost of ownership
No treadmill is completely maintenance-free, and some even require regular maintenance to protect the warranty. Most treadmill maintenance is relatively low-cost. Plan on adjusting bolts to keep the belt in line, vacuuming or wiping down the belt and deck, and occasionally applying lubricant. Some decks are specifically designed not to be lubricated, so check your owner's manual first for maintenance requirements and limitations.