T Nation

Smith Machine

Hey guys I’m looking for an article about the sheering force that the smith machine puts on your knees and back if you squat with it. I thought there was one on t-mag but can’t find it in the search. Is there one some where? Or do any of you know of research supporting this claim? Any info would be good. Thanks!

I seem to recall that the ISSA personal training study guide said something to this effect. Basically Hatfield ranting about why the free squat kicks so much ass. I quit being a personal trainer awhile ago, but if I can track down my manual tonight I’ll check it out.

Matt, thanks. I have a strength training class and I asked my teacher about it but she didn’t know for sure, and asked if I could find any research that was done on it. If you find something that would help me out. Thanks again.

Check those “smart training” articles from way back in t-mag. It’s an interview with a chiropractor and I think he talks some about that topic.

Check Poliquins book

Page 72 of “The Poliquin Principles” states the following: “The smith bar makes it possible to squat in a manner that allows you to lean back against the barbell, thereby supporting your back and minimizing hip extension during the exercise. What this does is take the hamstrings out of the movement. The hamstrings, however, are the muscle group that helps stabilize the kneecap. The result is unusually high shearing forces that try to pull the joint apart, as well as tremendous stress on the ACL…”

Hope that helps.

Mr. Science here. Technically squats aren’t applying ‘sheer’ force. The femur is always over the tibia. Leg extensions apply sheer force though.

Tc, thanks that was exactly what I was looking for.

Sorry it took me so long to get this. In the ISSA training manual, Hatfield (I assume) writes that “destructive shear forces in the knee can be as much as 30% higher in the hack and Smith squats than with conventional techniques.” Hope this helps.