Alright, I've been silent long enough. BULLSHIT!!! The Smith machine is NOT the dreaded knee/back destroyer that it's claimed to be. The only reason I've heard so far is that it forces you to move in a single plane which isn't natural, therefore it MUST be bad. Again I say BULLSHIT. If that were the case then the linear leg press would be getting lambasted every bit as much as the Smith machine.
As a matter of fact, in some cases the Smith is superior to regular squats. For people with little or no Achilles flexibility, it allows them to place their feet a bit forward of the bar, keep all the weight on their heels. This isolates the quads and takes stress off the knees.
Are Smith machines better than free weight squats? Of course not but, that doesn't make them bad.![]()
The torque on the knee joint is different. The center of mass you are fighting against isn't so far away from your knee on a leg press. If you place your legs on the leg press properly, there is not as much shearing force on the knee joint.
Again, there are other ways around issues with ankle mobility. Firstly, you should address the problem if you know it's there rather than just working around the problem. Second, there are other alternatives, like split squats or powerlifter style box squats, which don't require as much ankle mobility.