# Are Leg Extensions bad for you?



## Gunzz160 (Mar 27, 2007)

I have heard this time and time again by people saying that you can develope water around your knee joint and that they arn't good for you. Any truth to this?


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## NeilPearson (Mar 27, 2007)

I think that is how I herniated a disk in my back


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## AKIRA (Mar 27, 2007)

To tell you the truth, I was thinking of the biomechanics of the knee a few days ago and I cant quite picture the movement of the knee being different from a squat.

Actually, the only difference I can think of is that the weight is placed on the top of the shins instead of directly above the knee.  

If this is a good start in understanding the difference in the extension/flexion of the knee, let me know.

P?  Cow?

Did Cow get slaughtered?  Where the fuck has he been?


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## Duncans Donuts (Mar 27, 2007)

doing leg extensions, don't let the resistance go the entire 90 degrees from full extension (i do 4/5 of the total range of motion) - this keeps tension on the quad group as well as prevents higher shearing force on the knees.

no leg extensions are not bad for you


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## Goodfella9783 (Mar 27, 2007)

Duncans Donuts said:


> doing leg extensions, don't let the resistance go the entire 90 degrees from full extension (i do 4/5 of the total range of motion) - this keeps tension on the quad group as well as prevents higher shearing force on the knees.
> 
> no leg extensions are not bad for you


 
So basically don't extend your leg completely straight?


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## KelJu (Mar 27, 2007)

Duncans Donuts said:


> doing leg extensions, don't let the resistance go the entire 90 degrees from full extension (i do 4/5 of the total range of motion) - this keeps tension on the quad group as well as prevents higher shearing force on the knees.
> 
> no leg extensions are not bad for you



That makes a lot of sense actually. I might start throwing them back in my training every now and then, but only go 4/5 the way. 

I would also like to get others opinion on this.


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## Duncans Donuts (Mar 27, 2007)

i mean away from leg extension, when the knees are flexed.  don't allow the shins to go further than a 90 degree angle relative to thighs.

if you let your knees continue to flex, you are removing tension from the thighs.  that is why you do 4/5 of the way, to prevent shearing and maintain tension.


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## Goodfella9783 (Mar 27, 2007)

That may be hard to do considering some machines may start past that 90 degree angle. At least the ones on home gyms that aren't adjustable. I'm going to go check out the extension part of my bench real quick.


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## CowPimp (Mar 27, 2007)

I've read far too many suggestions from fitness professionals suggesting you have to make various alterations (Though they don't always agree entirely) to the movement in order to prevent unwanted shearing forces on the knee.  I just avoid it because there are plenty of other exercises out there that are less controversial.


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## P-funk (Mar 27, 2007)

CowPimp said:


> I've read far too many suggestions from fitness professionals suggesting you have to make various alterations (Though they don't always agree entirely) to the movement in order to prevent unwanted shearing forces on the knee.  I just avoid it because there are plenty of other exercises out there that are less controversial.



same.


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## AKIRA (Mar 27, 2007)

Goodfella9783 said:


> T*hat may be hard to do considering some machines may start past that 90 degree angle. *At least the ones on home gyms that aren't adjustable. I'm going to go check out the extension part of my bench real quick.



That is true.  Every leg extension machine begins before 90 degrees.

I really want to attack this shit.  I want to know, in its simplest form why it could be detrimental.

Expect newbie questions to simplify the result...


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## slip (Mar 27, 2007)

Havent had any noticeable bad sensations in my knees from them, but definately see the potential for Bad Things.

On a related note, started using more weight on the seated hamstring curl machine (up to 220lb) for 10 reps and have a strange sensation in my knees afterwards.  Definately some uncool forces going through them at that weight.


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## blueboy75 (Mar 27, 2007)

I do single leg extensions as a light warm-up before commencing my squats - feels pretty good for me.


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## P-funk (Mar 28, 2007)

AKIRA said:


> That is true.  Every leg extension machine begins before 90 degrees.
> 
> I really want to attack this shit.  I want to know, in its simplest form why it could be detrimental.
> 
> Expect newbie questions to simplify the result...



an open chain movement of that nature (ie underload) can lead to greater amounts of shear force as it pushes the patella back into the joint.  Hence the reason people say start the life at an angle >90 degrees.


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## AKIRA (Mar 28, 2007)

I suppose you can adjust the machine to make it start at or passed 9 0 degrees, but the ROM would be shortened.  And if the ROM is shortened, then the workout isnt as effective.

I personally havent ever had knee problems on the machine, but thats not why I dont do them.  I dont do them cuz of the warnings and the boredom.

I always felt my legs;s muscles near the knee being worked and sore.  Never anywhere up my leg near my torso.


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## ponyboy (Mar 28, 2007)

CowPimp said:


> I've read far too many suggestions from fitness professionals suggesting you have to make various alterations (Though they don't always agree entirely) to the movement in order to prevent unwanted shearing forces on the knee.  I just avoid it because there are plenty of other exercises out there that are less controversial.



I would agree with this.  I haven't done one in years.


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## Duncans Donuts (Mar 28, 2007)

AKIRA said:


> I suppose you can adjust the machine to make it start at or passed 9 0 degrees, but the ROM would be shortened.  And if the ROM is shortened, then the workout isnt as effective.



To the first point:

with most leg extension machines, 100% of the load is imposed when the leg is fully extended.  0% of the load is imposed on muscle at 90 degree flexion.  Therefore shortening the ROM will actualy increase tension time and make the workout MORE effective by not allowing for any relief of tension.


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## Dale Mabry (Mar 28, 2007)

AKIRA said:


> To tell you the truth, I was thinking of the biomechanics of the knee a few days ago and I cant quite picture the movement of the knee being different from a squat.
> 
> Actually, the only difference I can think of is that the weight is placed on the top of the shins instead of directly above the knee.
> 
> If this is a good start in understanding the difference in the extension/flexion of the knee, let me know.



The difference is in hip flexion.  At the bottom of the squat, your hip is flexed more than in a seated leg extension, this puts the rectus femoris in a shortened state.  Since it is biarticulate, you have to consider motion at both joints.


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## Phred (Mar 28, 2007)

Dale Mabry said:


> The difference is in hip flexion.  At the bottom of the squat, your hip is flexed more than in a seated leg extension, this puts the rectus femoris in a shortened state.  Since it is biarticulate, you have to consider motion at both joints.


 yea ...what he said.


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## VILBAUGH (Mar 28, 2007)

the answer is simple; 
the movement on the "leg extension" is not functional.

Every time you get off a chair, you squat....very functional.


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## Duncans Donuts (Mar 28, 2007)

VILBAUGH said:


> the answer is simple;
> the movement on the "leg extension" is not functional.
> 
> Every time you get off a chair, you squat....very functional.





Doing leg extensions will improve your general strength in the quad femoris group, which will help you in the real world with things that require general leg strength.  Period.  Functional is a buzz word.  Bench presses aren't functional.  Seated presses aren't functional.  Silly.


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## Nate K (Mar 28, 2007)

Why would you want to do seated presses?


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## P-funk (Mar 28, 2007)

Nate K said:


> Why would you want to do seated presses?



so that you don't have to stand up.


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## slip (Mar 29, 2007)

Nate K said:


> Why would you want to do seated presses?



Why would you want to do standing presses?


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## VILBAUGH (Mar 29, 2007)

Why would you want to do standing presses?

Anytime I ever lift a load overhead while living life outside the gym is in the standing position, so why sit down? 

what if you had to do more than 4-20 reps? say lifting people or sand bags or boxes of bannanas or anything, Im pretty sure you'd want know how to lift it while standing and maybe have a little support from your hips while doing it....


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## VILBAUGH (Mar 29, 2007)

bench press is definitly functional, your pushing a load off and away from your body, if it were any other situation, like being pinned, I couldn't see myself bringing the load behind my head for a "tricep extension", that to me would be silly. 

however you are right about one thing, seated pesses are not functional.

serious powerlifters will pin the bottom of the stack on a leg extension apparatus and achieve many reps having never used it. 
only squatting.


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## slip (Mar 29, 2007)

VILBAUGH said:


> Why would you want to do standing presses?
> 
> Anytime I ever lift a load overhead while living life outside the gym is in the standing position, so why sit down?
> 
> what if you had to do more than 4-20 reps? say lifting people or sand bags or boxes of bannanas or anything, Im pretty sure you'd want know how to lift it while standing and maybe have a little support from your hips while doing it....



I was merely making a point that there are many ways to do things, and many reasons to do things different ways.


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## Duncans Donuts (Mar 29, 2007)

VILBAUGH said:


> bench press is definitly functional, your pushing a load off and away from your body, if it were any other situation, like being pinned, I couldn't see myself bringing the load behind my head for a "tricep extension", that to me would be silly.
> 
> however you are right about one thing, seated pesses are not functional.
> 
> ...




what do i care what powerlifters do?

leg extensions increase cross-sectional space of muscle, thus increasing force output, thus increasing strength.  

squats do the same thing but through more degrees of freedom. 

i would pick squats over leg extensions any day, but i wouldn't throw the baby out with the bathwater.  leg extensions are safe and have great benefit.  functional is a buzz word.  laying on your back and bench pressing is *NOT* functional to any activity you might encounter in every day life.


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## Duncans Donuts (Mar 29, 2007)

VILBAUGH said:


> Why would you want to do standing presses?
> 
> Anytime I ever lift a load overhead while living life outside the gym is in the standing position, so why sit down?
> 
> what if you had to do more than 4-20 reps? say lifting people or sand bags or boxes of bannanas or anything, Im pretty sure you'd want know how to lift it while standing and maybe have a little support from your hips while doing it....



to increase muscle size in your DELTOIDS, clearly.

don't dismiss exercises because they don't fit your view of training.  why would i be lifting people or sand bags or boxes of bananas??  if that were a part of my job, I certainly wouldn't compound the overuse of those muscles by incorporating MORE standing lifts in my routine.


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