The four technologies of training equipment are constant resistance devices, variable resistance devices, accommodating resistance devices, and static resistance devices. All four types can be used with much benefit, as they help add variation to a training program.
“Constant resistance” means that the resistance or weight does not change during the course of the exercise. These types of devices include dumbbells, barbells, and machines with round pulleys. A constant resistance device does not correct for changed in musculoskeletal leverage that occurs during an exercise movement. Meaning when a weight is lifted, the body’s leverage changes during the joint movement. These devices also do not correct for reduced force output stemming from fatigue. A lot of sports scientists maintain that constant resistance training is more natural; it conforms to the way the body is intended to move. They believe that this makes this type of training more effective overall.
Variable resistance devices were engineered to cause the amount of weight to increase during an exercise movement. The idea is to utilize the overload principle which says that by maximizing the level of stress on the muscles by causing them to work as hard as possible throughout the full range of motion. A main drawback of all machines, including variable resistance devices, is that the movement is directed. Because of this, stabilizer muscles that would normally assist in the movement are not stressed, and therefore never grow and adapt to the movement. Another disadvantage, according to some experts, is that due to the unnatural movement, the brain centers that interpret force and movement pattern become confused. This can possibly slow and limit final potential.
Accommodating resistance devices maintain resistance by controlling the speed of movement throughout the exercise movement. One advantage to this machinery is that maximum force can be exerted throughout the entire movement, which increases the amount of adaptive overload that is applied during the exercise. The disadvantage these devices share with variable resistance devices is that the movement is unnatural; the brain does not accept the strangeness of controlled speed.
Static resistance devices stem from isometric exercise. This type of training will make you stronger, which is an advantage. However, in order to strengthen muscles throughout an entire range of movement, the muscles must be worked throughout the entire range of movement. Therefore, the main disadvantage is that the muscles will only be strengthened in that particular position.
Knowing about the different types of devices can help when you are creating your training plan. You can attack the same muscle from different angles, just by changing the type of device you use!