Heart rate programming considers your age and weight and will help you achieve an exercise level to achieve maximum fat-burning or cardiovascular benefits. Any treadmill that allows you to factor in these features provides you with a more personalized workout. I recommend these features for those over 200 pounds who may be just beginning a workout regimen. Check for warranties. Most cover manufacturer defects, not normal wear and tear.
Many machines come with a lifetime warranty on the frame.
The coverage on features and components may be different, ranging from 90 days to 3 years depending on the quality of the machine. You may be able to buy a renewable extended warranty that covers everything from parts to labor. Be a common sense consumer. Think about your actual needs and don't let the sales people sell you the most expensive machine if you do not want or need all the bells and whistles offered. Try it out and ask questions.