Defense:Standard weight machines provide a great alternative to free weights due to the cam system involved. Research confirms that they increase muscle strength just as well as free weights.
Prosecution:FreeMotion machines allow movement in multiple directions, as compared to standard weight machines, which move in a fixed path. Research has found that these machines provide better benefits than standard machines.
The cams of standard weight machines mimic the force/length curve of the target muscle. This allows for the resistance (weight) to be maximized when the muscle is in its strongest point in the range of motion of the exercise.
One study from Valdosta State University (Georgia) found that subjects training on a chest press machine for 10 weeks increased their strength on the free-weight bench press by the same amount as subjects training with the free-weight bench press.
A study from Globe University (Shakopee, Minnesota) found that subjects training on FreeMotion machines for 16 weeks increased muscle strength by almost 60% more than subjects training on standard weight machines. The Globe University researchers also found that the group using FreeMotion machines increased their balance by about 200% more than the group using standard weight machines.
VERDICT: FREEMOTION MACHINES
FreeMotion machines allow for a freer range of motion, prompting you to use more stabilizers than standard weight machines, which work in a fixed path. This may permit greater strength increases with FreeMotion machines.
If your gym is equipped with FreeMotion machines, use them in addition to free-weight exercises. Of course, your best bet is to use all the tools that your gym provides, including standard weight machines. On most workouts do machine exercises (either FreeMotion or standard weight machines) after doing free-weight exercises.