A treadmill is a device generally for walking or running while remaining in the same place. Treadmills were introduced before the development of powered machines, to harness the power of animals or humans to do work, often a type of mill that was operated by a person or animal treading steps of a treadwheel to grind grain. The term treadmill originally referred to an apparatus for determining wind speed and direction, and later came to refer only to the workout device.
Treadmills are usually powered by an electric motor, but can also be powered by a flywheel. Early versions included features such as metal teeth on the belt that would engage with notches on the flywheel, making it difficult to keep the belt moving at high speeds; this problem was solved withvention of the frictionless roller-and-roller principle used in modern treadmills.
The key advantage of treadmills over other forms of exercise is that they provide a controlled environment in which exercise can be conducted regardless of weather conditions outside. Treadmills also offer heart rate monitoring and other feedback options that allow users to exercise within their target heart rate zone for maximum cardiovascular benefit. Another advantage is that because they are self-powered, they do not require access to an electrical outlet, which makes them much more portable than some other types of exercise equipment such as elliptical trainers and stair climbers.
There are several factors that contribute to how quiet a treadmill is. The first is the quality of construction - if there are loose parts or poor fitment between components, this will create more noise as everything vibrates against each other while in use. Second is whether or not it has shock absorbing deck - this helps reduce impact noise when your feet hit the belt during use. Thirdly, Belt size also plays into things - wider belts tendto be quieter than narrower ones because there's less contact area between belt and deck/roller (this also contributes tobelt longevity). Lastly, Motor size/type affects things as well - direct drive motors located underneathentire deck tendto create less noise than induction motors located in front or rear endcaps because there's no mechanical transmission components involved (belts/pulleys/etc.).