Performing exercises on machines that make use of weight stacks is quickest way to rapidly adjust the amount of weight being lifted. This can be particularly effective when weight training with a workout buddy. The ability to change with weight amount by simply pulling out a pin and placing it back allows individuals to maintain elevated heart rates by not taking the time to exchange weight plates. For example, let's take 2 people: person A can do 150lbs tricep Push-Downs on the cable machine while person B can do 95lbs. Rather than having to add a 45lb plus a 10lb plate (and also remove it) after each set, the can seamlessly exercise together using the weight plates.
Drawbacks To weight stacks
With weight stacks being so easy to use, it is important to keep in mind their limitations and shortcomings. For those serious about weight lifting, as bodybuilders are, the amount of weight available for use in weight stacks is often not adequate to provide the desired workout and results they are looking for. There are a few solutions to this problem. Some cable machines have settings to add more resistance to the stack. This is usually done by moving a special pin or setting on the machine (not on the weight stacks themselves). Another method is to add additional rectangular weight plates to the stack. These are special plates with groves in specific areas that allow them to slide up the cylinders that run through the stack as it rises from the exercise motion. The third method, and sometimes frowned upon, is to run the pin through a circular weight plate. While this does add a significant amount of weight, it can bend the pin, thus making it unusable to thread through the weight stack.
The reliance upon pins is what makes the use of weight stacks fall short of the weight plate or dumbbell/barbell alternatives. Often in gyms, the pins will become misplaced by moving around machine to machine or even if they are secured to a specific machine, through wear and tear, become bent and disfigured. It is possible to still use pins in this condition but it can take some finagling and potentially slow down the workout.
As with any type of device used for weight lifting exercises, weight stacks have their own set of safety concerns to be aware of. Aside from the moving parts of the exercise machines themselves, it is advised to keep body parts away from the stack at all times. The plates on the stack have been known to "stick" from time to time. When one is performing exercises, the stuck plates can fall, crashing down into the stationary portion of the stack, causing injury, or at least startling the individual.