A weight machine is an

exercise machine An exercise machine is any machine used for physical exercise. These range from simple spring-like devices to computerized electromechanical devices to recirculating-stream swimming pools. Most exercise machines incorporate an ergometer. An ergo ...

used for

weight training Weight training is a common type of strength training for developing the strength, size of skeletal muscles and maintenance of strength.Keogh, Justin W, and Paul W Winwood. “Report for: The Epidemiology of Injuries Across the Weight-Trai ...

that uses gravity as the primary source of resistance and a combination of

simple machine A simple machine is a mechanical device that changes the direction or magnitude of a force. In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. Usually the term ref ...

s to convey that resistance to the person using the machine. Each of the simple machines (pulley, lever, wheel, incline) changes the

mechanical advantage Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for ...

of the overall machine relative to the weight.

Stack machines

A ''stack machine''—also called a ''stack'' or ''rack''—has a set of rectangular plates that are pierced by a vertical bar which has holes drilled in it to accept a pin. Each of the plates has a channel on its underside (or a hole through the middle, as visible in the picture) that aligns with one of the holes. When the pin is inserted through the channel into the hole, all of the plates above the pin rest upon it, and are lifted when the bar rises. The plates below do not rise. This allows the same machine to provide several levels of resistance over the same range of motion with an adjustment that requires very little force to accomplish in itself. The means of lifting the bar varies. Some machines have a roller at the top of the bar that sits on a lever. When the lever is raised the bar can go up and the roller moves along the lever, allowing the bar to stay vertical. On some machines the bar is attached to a hinge on the lever, which causes swaying in the bar and the plates as the lever goes up and down. On other machines the bar is attached to a cable or belt, which runs through pulleys or over a wheel. The other end of the cable will either be a handle or strap that the user holds or wraps around some body part, or will be attached to a lever, adding further simple machines to the mechanical chain. Usually, each plate is marked with a number. On some machines these numbers give the actual weight of the plate and those above it. On some, the number gives the force at the user's actuation point with the machine. And on some machines the number is simply an index counting the number of plates being lifted. The early

Nautilus The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in ...

machines were a combination of lever and cable machines. They also had optional, fixed elements such as a chinning bar.

Universal Gym Equipment Universal Gym Equipment was an American manufacturer of exercise equipment, in particular weight machines. It was founded by Harold Zinkin in 1957. In 1998, it was acquired by Flexible Flyer. In 2006 it was acquired by Nautilus, Inc. The Univers ...

pioneered the multi-station style of machines. Stack Machine in use in commercial gym

Plate-loaded machines

''Plate-loaded machines'' (such as the Smith machine or sled-type

leg press The leg press is a compound weight training exercise in which the individual pushes a weight or resistance away from them using their legs. The term ''leg press machine'' refers to the apparatus used to perform this exercise. The leg press can be ...

) use standard barbell plates instead of captive stacks of plates. They combine a bar-end on which to hang the plates with several simple machines to convey the force to the user. The plate-loaded machines will often have a very high mechanical advantage, due to the need to make room for large plates over a large range of motion following a path that causes them to converge at one end or the other. Also, the motion will generally not be vertical, and the net resistance is equal to the cosine of the angle at which it is moving relative to vertical. For example, consider an incline press machine that is a single-lever machine that has the plates halfway up the lever from the handles to the

fulcrum A fulcrum is the support about which a lever pivots. Fulcrum may also refer to: Companies and organizations * Fulcrum (Anglican think tank), a Church of England think tank * Fulcrum Press, a British publisher of poetry * Fulcrum Wheels, a bicy ...

, and begins moving the plates at a 45- degree angle from vertical. The lever will provide a leverage advantage of 2:1, and the incline will have an advantage of 1:√2/2, for a net mechanical advantage of . Thus () of plates will apply to the user only an equaling weight of or a force of at the beginning of the motion. On the other end of the spectrum may be a bent-over-row machine that is designed with the user's grip between the plates and the fulcrum. This amplifies the force needed by the user relative to the weight of the plates.

References

{{DEFAULTSORT:Weight Machine Weight training equipment Machines

Stack machines

Plate-loaded machines

See also

References