This article will try to separate some of the fact from the fiction of each of these types of training tools. At the end of this article it will make more sense as to why one would choose a free-weight or a machine and for what purpose.
Before we dive into the major differences between free weights and machines let us first agree on what we are calling a free-weight or a machine.
A free-weight can be classified as any object or device that can be moved freely in three-dimensional space. Some of the more common free-weights found in a gym would be:
3. High/Low or adjustable pulley system
4. Lat pull-down and low-row device
5. Medicine Balls(all types including kettle bells)
6. Ankle weights
7. The human body the ultimate free-weight of all!
In all reality, any object that is free to move in three-dimensional space that is not fixed to any specific set of axis (as in a smith machine) can be considered a free weight. An exercise machine on the other hand, is not allowed to move in three-dimensional space and is usually only capable of moving in two dimensions.
Any exercise machine in a gym such as a pec-dec or a smith machine is a perfect example of what we are calling high-tech training apparatus.
So which is best, free-weights or machines? I would assume that most of you reading this article are frequent users of free-weights and cable systems.
However, I also know that many bodybuilders choose machine training for isolating and really targeting a specific muscle or group of muscles. So to answer the question on the superiority of free weights versus machines it is first important to know what one's goals are.
Structural Vs. Functional Goals
In studying human physiology we learn that structure and function are intimately related. In strength training jargon this means that if you want to change your structure (i.e. build mass) you must change the function of that structure (i.e. improve 8-12RM) which is ultimately a neuromuscular phenomenon.
So if ones wishes to gain mass (hypertrophy), one must change the function on the nervous system's ability to use that muscle (i.e. get stronger) so that the structure (soft-tissues) can adapt and grow.
The average reader on a web site called Bodybuilding.com is probably most interested in structural goals like building mass and losing body fat than say a sprinter, who is mainly concerned with improving a specific function (running 100m dash in 10 seconds) and thus prioritizes functional goals over structural ones.
This does not mean that sprinters omit structural phases in their training. It simply states that the main goal for a sprinter is not to get as big as a house but rather to improve a specific skill (run fast) which requires that the function of the neuromuscular system improve along with the structure.
Getting back to our discussion of free-weight versus machines, it helpful to know the main benefits of each in relation to whether we have primarily structural or functional goals. Free weights, with their extreme versatility are the ultimate tool for both structural and functional goals.
For instance if a bodybuilder is bench pressing and wishes to put on mass, a choice of reps in the 8-15 range would make a good choice. If one is also a football player who desires to put on some mass the bench press again is an excellent choice because it develops more real-life strength.
What is often called functional strength due to the need to stabilize and control the barbell in all three planes of motion, just like the athlete will need to do on the playing field.
However if the football player decides to use all high-tech Hammer strength machines for his chest work he may build some impressive pecs but will be lacking in the function department due to the lack of three-dimensional stability required in those exercises. Thus, his structure would have improved but without a corresponding increase in his function.
Now lets look at a scenario where a bodybuilder, who's chest development has been stuck for some time. His workouts usually consist of free-weight only with some standing cable fly's thrown in to finish off his chest workout.
If this person were to add some machine work at the end of his free-weight workout he may be able to add some more volume and thus trigger some new growth. After his traditional free-weight workout, his shoulder stabilizers may be so fatigued that his chest is unable to get more work during his final sets.
However, by finishing off with some machine training he may be able to exhaust and stimulate more pectoral muscle fibers because the machine is taking some of the load off his rotator cuff. This is a scientific application for the use of machines.
For the vast majority of exercises and goals, whether structural or functional, free-weights usually offer the most variety as well as total body stimulation because many muscles other than the prime movers (muscles responsible for moving the load) are stimulated as stabilizers.
Machines on the other hand, with their ability to isolate better, can be useful for structural or bodybuilding purposes when they are carefully planned in the workout which is usually to place them after all free-weight exercises. There is much more to the story here.
Hopefully, this article has shed a little light on the differences between free-weights and machines and specifically the scientific use of each in regards to your training goals.