Are Squats on the Smith Machine bad for your knees?

[Nelson Montana]

mt: Most of the movements you mentioned are natural, just not under the stress that resistance training would provide. You're correct about the leg curls though. They too are an unnatural movement to a degree but hamstring muscles do "pull up" when running so it isn't as bad as extentions.

Because any movement is a little awkward doesn't mean you can't strengten the muscles by using them. A leg curl uses body torque to a degree, which is why standing leg curl you can never use much weight. Compare that to how much weight you can squat. That's my point. If you want to build a big muscle , you need to use a heavy weight.

Nothing is written in stone. This is why I argue with people who are so opposed to the Smith machine, claiming it isn't "natural." People claim presses behind the neck aren't natural and I never had a problem with them. Hell, lifting tons of weight isn't natural! But knees are delicate. They injure easily and take forever to heal, so it's prudent to work with the bodies natural movement as opposed to forcing it to get stronger by stressing it in a compromising way.

 

[psychedout]

Squats don't hurt my knees at all. Albeit reg, front, box, smith.

Leg extensions and leg press kill my knees -- I never do those.

 

[mt]

NM: Fair enough. Though I still think the leg extension is a natural movement. At least it is for me. Though most of my martial arts training is spent rolling on the ground I'd still rather begin and end a fight with a swift kick to the nuts. And being 6'2" and all legs I find getting into a full squat position, especially with the feet flat on the ground and not warmed up, to be rather awkward.
But having long legs isn't all bad. I look great in blue denim "Daisey Duke" shorts with black combat boots.

 

[visions]

If you insist on doing leg extensions there is no need to go beyond 30degrees range of motion, EMG's show full VMO contraction within the first 30degrees so basically your vastus (quads) groups get the same benefit contraction wise as would going in the full range of motion. But like some have said here the leg extension from a functional standpoint is virtually worthless.

 

[mt]

If you insist on doing leg extensions there is no need to go beyond 30degrees range of motion, EMG's show full VMO contraction within the first 30degrees so basically your vastus (quads) groups get the same benefit contraction wise as would going in the full range of motion. But like some have said here the leg extension from a functional standpoint is virtually worthless.

It seems unlikely that it is worthless as the muscle is being worked. It is a common movement for rehab and I don't know a single competitive bodybuilder that doesn't do leg extensions. I like it for a pre-exhaust movement. Just the fact that I can't do as much weight for the same number of reps on a pressing type movement (squats, leg presses...) when doing leg extensions immediately prior tells me that some time of load on the muscle is being applied.

 

[visions]

It seems unlikely that it is worthless as the muscle is being worked. It is a common movement for rehab and I don't know a single competitive bodybuilder that doesn't do leg extensions. I like it for a pre-exhaust movement. Just the fact that I can't do as much weight for the same number of reps on a pressing type movement (squats, leg presses...) when doing leg extensions immediately prior tells me that some time of load on the muscle is being applied.

"from a functional standpoint is virtually worthless." I did not say from a bodybuilding standpoint and I even stated that within the first 30 degrees of range of motion there is a full contraction measured through an EMG so clearly there is a contraction and with a loaded contraction comes hypertrophy so yes if hypertrophy is your only goal leg extensions can serve a purpose but why even bother isolating the joint when you could better spend your time on compound movements that generate more motor unit recruitment which in turn can not only improve your functionality but also give you the hypertrophy that you're hoping to gain. Just MO.

 

[mt]

"from a functional standpoint is virtually worthless." I did not say from a bodybuilding standpoint and I even stated that within the first 30 degrees of range of motion there is a full contraction measured through an EMG so clearly there is a contraction and with a loaded contraction comes hypertrophy so yes if hypertrophy is your only goal leg extensions can serve a purpose but why even bother isolating the joint when you could better spend your time on compound movements that generate more motor unit recruitment which in turn can not only improve your functionality but also give you the hypertrophy that you're hoping to gain. Just MO.

I am going by the assumption that leg extensions will strenghten your quads. And a stronger muscle, any muscle, is an improvement in functional ability.
And I do agree that compound movements such as squats are an overall better exercise but, well, they're kind of hard. I mean, you get all out of breath and sweaty and stuff. It's so much nicer to sit comfortably in an ergonomically designed machine and leisurely kick your leg out 30 degrees or so. Some people can even read the paper when doing leg extensions. Try doing that with a heavy barbell on your neck.

 

[javaguru]

After my ACL surgery I was told, "Do not do leg extensions, it's a terrible exercise for your knees." I was treated at a top teaching hospital by one of the best sports medicine guys in the USA. Of course, I hadn't done them for five years anyway so....

 

[visions]

I am going by the assumption that leg extensions will strenghten your quads. And a stronger muscle, any muscle, is an improvement in functional ability.
And I do agree that compound movements such as squats are an overall better exercise but, well, they're kind of hard. I mean, you get all out of breath and sweaty and stuff. It's so much nicer to sit comfortably in an ergonomically designed machine and leisurely kick your leg out 30 degrees or so. Some people can even read the paper when doing leg extensions. Try doing that with a heavy barbell on your neck.

EXACTLY, when taken into consideration the scientific principles of training, specifically SAID or Overload which basically state through compensation the body adapts to a stimulus and without any complexity the body will plataue and no longer make progressive gains. Yes with the contribution of anabolics your leg extension strength will continue to go through the roof as will the integrity of your patellar tendon and ligaments around the knee joint but hey at least you can still get a newspaper read in. No I'm just playin but anybody on this board knows variety is the most essential key to training, so I'm just saying that both the mind and the body can far greater benefit from compound functional movements. Also on a side note, studies show that (I'll find it if you want me to) that there is NO transfer in strength from isolated joint movements to compound movements, in other words extending your leg to death will not transfer into strength gains in the squat.

 

[mt]

Also on a side note, studies show that (I'll find it if you want me to) that there is NO transfer in strength from isolated joint movements to compound movements, in other words extending your leg to death will not transfer into strength gains in the squat.

That is very interesting. Does that also apply to other muscle groups? For example, does having stronger biceps from doing curls help you with pullups? Or increasing the strenght of your triceps by doing push downs help you with your bench? It does seem counter intuitive but personal experience has led me to believe that the body is very "activity specific" for lack of a better term. Meaning, that if you want to be good, strong or in condition to do that something the only way to do it is to specifically do that something. For example, it is beginning to dawn on me that interval running (sprints/jog) and just regular running doesn't really seem to help my conditioning in submission wrestling/Jiu-Jitsu. What I mean by that is my conditioning in regard to wrestling doesn't seem to change if I stop running. But if I just run but don't wrestle (say, due to injury) my endurance on the mat takes a big dive. So, I am coming to the conclusion, and I know this is a leap, that if I want to be in shape to wrestle I have to wrestle and if I want to get stronger in squats I have to squat.