Additional key elements in the movement of weight resistance are: 1) the size of the muscle groups involved, and 2) the distance the resistance has to travel. The more muscles used in an exercise the greater the weight resistance that can be lifted. The shorter the distance the weight resistance moves the heavier the weight that can be lifted. This is why more weight can be handled in a squat as compared to a curl; a half-squat as compared to a full squat.
The equipment for weight resistance exercise comes in t wo forms; machines, and free-weights. A free-weight is a bar on which iron or rubber discs can be loaded. There are many types of free weight bars. They can be made from stiff steel with inner collars, or from flexible steel with frictionless outer collars on the outside. The larger weight resistance you lift, the more critical the quality of the bar's spring and rotation becomes. However, it's not the equipment that you use but the quality of your workout planning that ultimately produces your results.
The term free-weight describes a barbell's ability to allow your body to have complete freedom of movement. There is a specific free-weight exercise for every muscle group. With free-weights you can do full body exercises. Free-weights exercising makes equal right/left proportion, balance, coordination and strength to develop. From this standpoint the free-weight is superior to any machine. The main drawback to free-weights is that you usually have to stand upright when using them. They are unforgiving and can be dangerous if dropped unexpectedly. It is easier to break form with free-weight since concentration is required to maintain the correct technique.
The invention and use of weight machines coincides with the world's leap into advanced technology. As people began to perceive the new mech/tech as being superior, the equipment companies designed intricate weight machines to replace the free-weights. Interestingly, these machines do the same movements that free-weights can do. Their main benefit is that you can use them while sitting down.
Weight machines are designed to isolate each muscle or muscle group, and to restrict the possibilities of breaking form. With the incorporation of a cam or hydraulics, they even limit the obstacle of the "sticking point". Cam machines (like Nautilus etc.) alter the leverage to adjust for strength variations through the full range of motion. The hydraulic machines (like Kieser etc.) use air pressure to push back and create accommodating resistance. By installing computers into these machines, they can even monitor work output making limited real-time adjustments to workload.
However, the weight machines are themselves compromises. In the real world, one size does not fit all. The short or tall person is at a disadvantage. It is not always possible to design a weight machine that follows the unique anatomical pathways of your body. There is no weight machine in the world that allows you to do full body exercise, the way that free weight does.
The BioFitness Institute demonstrates in detail the
correct way to do Body Building, Powerlifting, and Weightlifting
exercises. The exercises are demonstrated in the free-weight
movements that most machines copy. Because of this you can apply
the techniques to any machines you encounter. All the
demonstrations use sequenced graphics so that you can analyize
the proper form of the movement. They also include descriptive
text to understand them better. However, it's the quality of
your workout planning that ultimately produces your results.