Smith machines are very popular these days and have been for awhile now. Every decent gym has at least one of them. There are many people that enjoy using them, while others won't go anywhere near it.
I really do like to use the smith machine in my work out routines, but I also believe that the cons out weigh the pros. So what exactly are the advantages and disadvantages to using this popular piece of gym equipment?
Lets start with the advantages. It is by far safer than traditional free weights. You have the guidance of a linear path to follow throughout the movement, and the need for a spotter is reduced because you can turn your wrists and lock the bar into place in the frame of the machine. Another advantage is that you can usually lift more weight because you don't have to stabilize the weight your trying to lift.
Let us look at some of the cons. As stated above you are not using your stabilizing muscles so you are not getting all you could be getting from your chosen exercise. There is no need to balance the bar which will lead to the underdevelopment of important core muscle groups. This in turn may make you more likely to be injured during recreational or work related physical activities.
It is the teacher of poor form. There really aren't too many free weight exercises out there that use a straight up and down movement. Most have a slight arc or a slight bend in them somewhere. Your body is not allowed to make any natural adjustments to the movement of the lift which can cause muscle strains and tears.
Some other things to consider when using this piece of equipment is that you won't get as strong and big as fast as you would by using free weights. It really all leads back to the use of your stabilizing muscles and utilizing them during your exercises that will make a huge difference in your performance and results.
However, due to the isolated range of motion, this machine is helpful when returning to the gym after an injury. If you don't like the idea of a training partner you will be better off also. Keep in mind though that the machine does not eliminate the need for a good spotter.
When it comes down to it, it is of course a personal matter that you yourself will have to make. I lean towards the use of the smith machine in my routine because it seems to add balance to a workout. I like to use them at the end of a workout when I'm tired and not quite as strong as in the beginning.