Weight machines are exercise machines that typically are comprised of several smaller apparatuses, such as pulleys, levers, wheels, and inclines. These smaller apparatuses are the means of conveying and manipulating the amount of resistance a person wishes to work against. Weights also play an important role in any weight machine.
The stack machine, for instance, is comprised of several rectangular weight plates that are stacked and connected by a vertical bar drilled with holes at evenly spaced intervals. Holes in the bar coincide with a hole in each plate and are aligned by the placement of a pin or steel rod. Once a pin is placed in the connecting rod, the plates above the pin will rise when force is applied to the connected pulley, thus creating the desired affect of weight resistance. Plates typically weigh ten to 20 pounds and are labeled accordingly. Smaller removal plates of two to five pounds allow for further manipulation of weight resistance.
The Nautilus series of stack machines essentially work the entire body, including the quadriceps, hamstrings, gluteal, abdominal, and calf muscles in addition to the triceps, biceps, pectorals, shoulder, and back muscles. The plate-loaded machine, such as the Smith machine, is another popular form of the weight machine. Plate-loaded machines use standard barbells instead of plates in addition to lever and wheel apparatuses to convey the desired force.
A Smith machine consists of a barbell at either end of a fixed steel rail, allowing for vertical movement only. Because it cannot fall forward, backward, or sideways, the Smith machine generally is preferred over the standard barbell in regards to safety. In addition, the Smith machine consists of several vertical posts that are infused with slots in which the barbell can be secured at any time. This is especially helpful for people who exercise without a spotter or prefer to vary weight resistance throughout a routine. While the Smith machine is most often used for squatting, lunging, and various other leg strengthening exercises, it can also be used for push-ups, dead lifts, tricep dips, bicep curls, and rowing motions.
As with any weight machine, it can be important for a person to maintain form over added resistance as both a safety precaution and way of targeting the muscle group. Motions for both the stack weight machine and plate-loaded weight machine should be divided into three or four sets of eight to 15 repetitions. Rest periods of 30 seconds to two minutes between sets are generally recommended for anyone using a weight machine for exercise.