Walking into a well equipped weight room can be somewhat intimidating when you are new to weight training. As you look around, you will see machines of various sizes and shapes, short and long bars, and weight plates (that fit onto the bars) of different sizes/poundages with holes of different sizes. It can be confusing as well as intimidating. However, because the equipment that is available to you oftentimes dictates the exercises that you will be able to include in your workouts, becoming familiar with it is a logical first step in starting a weight training program. Also important is learning the “whys and hows” of equipment use that will help to avoid injury. This section will include information about the types, characteristics, and safe uses of machine and free weight training equipment.
Most machines in a workout facility are designed to accommodate what is referred to as a dynamic form of exercise—that is, exercises involving movement. In contrast are isometric exercises in which no observable movement occurs, such as pulling or pushing against a fixed bar. Dynamic exercises performed on weight machines typically challenge muscles to shorten against resistance and lengthen in a controlled manner while being “loaded”. Your fitness coach should demonstrate proper technique when using these machines
Fixed Resistance Equipment
The single unit pulley (a) and pivot arm (b) types of machines are designed to work primarily one muscle area. Multi unit machines have various stations attached to their frame, allowing many muscle areas to be worked by simply moving from station to station.
A closer look at the structure of these machines reveals how they are designed. The weight stack is lifted by pushing a weight arm attached to a fixed pivot point, and in the weight stack is lifted by pulling down on a handle affixed to a cable pulley arrangement. Sometimes a chain, or flat belt is used in place of the cable.
You will notice when using fixed resistance equipment that some movement phases require more effort than others, as though someone were changing the weight of the weight stack on you. Really what has happened is that as the weight arm moves in response to being pushed or pulled, it changes the location of the weight stack (WS) in relation to the weight arm’s pivot point (PP). This is illustrated in Figure 10. As the distance between the weight stack and the pivot point becomes shorter, the exercise requires less effort, and as the distance between these two points becomes greater, the exercise requires more effort. If you are familiar with leverage concepts, you understand the specific reasons for all of this.
Machines that feature a fixed pivot or the circular shaped pulley design are commonly referred to as fixed resistance machines. The limitation of this type of equipment is that the muscles are not taxed in a consistent manner throughout the exercise range. Free weights also fall into this category and present the same limitation.
Variable Resistance Equipment
In an effort to create a more consistent stress on muscles, some machines are designed to allow the weight stack to roll or slide back and forth on the weight arm of the machine. These machines are referred to as variable resistance machines. Note again the relationship between the weight stack and the pivot point as the stack moves. When the weight arm moves to a position that would require less effort with a fixed pivot machine, the weight stack on the variable resistance machine moves away from the pivot point. When it is pushed or pulled to a position requiring more effort, the weight stack moves closer to the pivot point. The result of these changes. There is more to understanding why a more consistent stress is imposed throughout the entire range of an exercise with the moving pivot, but the explanation here is sufficient to help you recognize the capabilities of these variable resistance machines.
To create a more consistent stress, variable resistance machines may also feature a somewhat kidney shaped wheel or cam. The effect of cam shape on weight stack location. As the chain (or cable or belt) tracks over the peaks and valleys of the cam, notice that the distance between the pivot point (the axle on which the cam rotates) and the weight stack changes. This variation in distance from the pivot point to the location of the weight stack is what creates a more uniform loading on muscles.