I wrote to Life Fitness (makers of Parabody equipment, and probably the gold standard Smith Machine) as a potential client. I was expecting to hear about how wonderful Smith Machines are (that would be a switch). What I received follows, and I thought it was a rather candid, honest reply dealing with the issues:
Thank you for your inquiry regarding the ParaBody Smith System. In regard to
your question regarding the safety of this type of machine especially as it
related to lower body joints, I would say there are many opinions on the subject
and I will offer you mine.
We have seen a large resurgence in the interest for and popularity of Smith
Machines in the last ten years. I believe this is primarily for two reasons:
1) Many personal trainers have introduced free weight lifting to novice lifters
(typically a little older) with a Smith Machine. This is because they can
perform the motion of the lift easier when the machine tracks the movement for
them. As well it is a safer lift because they are not trying to control a
completely free apparatus like an Olympic bar (especially if you are working out
at home alone). The down side to this is, as you say, is that the body does not
move completely in a linear manner. This means that any time your body wants to
move contrary to the direction the bar is moving, the machine is applying a
stress to the body in a different direction than it wants to go naturally. How
detrimental this stress is depends on the intensity of the stress and the
integrity of the joint supporting it.
2) Bodybuilders have used Smith Machines in order to "overload" certain muscle
groups with heavier weight loads than they could doing barbell squats.
As with anything, there are plusses and minusses. If you are looking for
something that can give you a higher degree of control (especially with heavier
loads) and greater safety when working out at home, the Smith may be your
answer. If you want something that allows totally free range of motion and
unencumbered lifting, I would look more closely at our Rack System or Power
System. Please let me know if you would like further information on any of these
I hope this helps a bit. Please let me know if you have any other questions.
Good luck in your selection process. We wish you the best in meeting your
Business Manager - Consumer Strength Products
14150 Sunfish Lake Blvd.
Ramsey, MN 55303