# Discussion on Muscle Friction



## Duncans Donuts (Mar 10, 2005)

I haven't seen any threads in this board's history discussing the relevance of muscle friction regarding concentric and eccentric exercise performance.  Any thoughts?


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## Du (Mar 10, 2005)

Duncans Donuts said:
			
		

> Any thoughts?


Ive got none.


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## DOMS (Mar 10, 2005)

du510 said:
			
		

> Ive got none.


 Quick, where's the 'surprised' icon...


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## ihateschoolmt (Mar 10, 2005)

Muscle friction causes you to lift heavier than you think your lifting. If you lift a 55 pound dumbbell muscle friction may be causing you to lift 55 pounds. But friction will make lowering the weight easier. With the same dumbbell you may be lowering 45 pounds. Muscle friction may also be partailly responsable for muscle soreness. That's what I was told, but I'm not sure if that has all been proven.


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## reg56 (Mar 10, 2005)

ihateschoolmt said:
			
		

> Muscle friction may also be partailly responsable for muscle soreness. That's what I was told, but I'm not sure if that has all been proven.


 I remember reading something like that. I believe muscle friction is somewhat responsible for soreness, among other things.

 As far as lifting speed goes, fast lifting creates momentum and doesn't promote blood flow to the muscle. Slow movement creates less momentum and less internal muscle friction. Slow lifting also requires a more even application of muscle power throughout the movement range which promotes rapid blood flow into the specific muscle you're training. To sum it up, the concentric, or positive phase of a lift should be performed faster than the eccentric (negative) phase. 1-2 seconds positive, 4-5 seconds negative.


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## ihateschoolmt (Mar 10, 2005)

Duncans Donuts said:
			
		

> concentric and eccentric exercise.


I know this is a stupid question, but what does that mean? I've never heard it and the definition in the dictionary doesn't make sence.


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## reg56 (Mar 10, 2005)

ihateschoolmt said:
			
		

> I know this is a stupid question, but what does that mean? I've never heard it and the definition in the dictionary doesn't make sence.


 Concentric is the positive phase of a lift in which the targeted muscle is actually doing the work. Eccentric is the negative phase where you are returning the weight back to its starting position(resistance).

 Correct me if I'm wrong...


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## ihateschoolmt (Mar 10, 2005)

reg56 said:
			
		

> Concentric is the positive phase of a lift in which the targeted muscle is actually doing the work. Eccentric is the negative phase where you are returning the weight back to its starting position(resistance).
> 
> Correct me if I'm wrong...


Wow, the dictionary definition wasn't even close. It said something about a center point.


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## P-funk (Mar 10, 2005)

> o sum it up, the concentric, or positive phase of a lift should be performed faster than the eccentric (negative) phase. 1-2 seconds positive, 4-5 seconds negative.



I usually don't dictate the speed of my concentric rather just think explosive.  But that is a good way to do it......explosive concentric followed by a slower eccentric.


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## Duncans Donuts (Mar 10, 2005)

Concentric is positive, eccentric is negative


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## ihateschoolmt (Mar 10, 2005)

The board needs more threads like this. I usually have to search for advanced  things like this.


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## CowPimp (Mar 10, 2005)

Concentric is where the muscle contracts under tensions.  Eccentric is where the muscle stretches under tension.


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## KarlW (Mar 10, 2005)

What is muscle friction anyway?

Friction against other muscles? or against bone? what?


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## Duncans Donuts (Mar 10, 2005)

Friction is a "force that resists the relative motion or tendency to such motion of two bodies in contact".  Muscles by nature (contracting and stretching) generate friction within themselves.


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## KarlW (Mar 11, 2005)

So the individual fibres create friction against one another?Why would that be? Is it because some fibres are contracting/stretching at a different rate to others?


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## CowPimp (Mar 11, 2005)

Perhaps muscle friction has something to do with the hypertrophy induction effects that eccentric motion has on skeletal muscle.  Perhaps there is more friction during the eccentric part, or something of the sort?  Just some random speculation; I've never looked into the topic of muscle friction.


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## Duncans Donuts (Mar 11, 2005)

Simply put, muscle friction works against your favor during the concentric contraction, and for your favor during the eccentric contraction.  This is why negative strength is greater than positive strength.  

Think of it like this:  assume a car is going uphill.  At this point, the car must overcome the load as well as several points of friction, including the tires on the ground and air resistance.  However, in wanting to control the descent as soon as the car overcomes the hill goes down, the friction works in your favor.  



> Think about it for a moment: how much force is required to lift 100 pounds of weight, at any *constant speed *of upwards movement?  The answer?  100 pounds of force, no more and no less; because, if you exert more than 100 pounds of upwards force, then the speed of movement would not remain constant; instead, the speed of upwards movement would increase.  So the fact that the upwards speed of movement remains constant is clear proof that the upwards force is exactly equal to the downwards force produced by gravity that is acting upon the weight.


This of course implies that, given a common cadence, the same amount of force used to move the load MUST EQUAL the amount of downward gravitational force imposed by the load.  So why is the negative part so much easier?  Look to the above example.  


> So the individual fibres create friction against one another?Why would that be?


Because everything that has motion and mass has friction..


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## ihateschoolmt (Mar 11, 2005)

CowPimp said:
			
		

> Perhaps there is more friction during the eccentric part, or something of the sort?


There is the same amount of friction in both, but it is helpful on eccentric and makes concentric harder. It would be like if you had to pull a 90 pound box up a 20 degree incline. Would you rather use a ramp with a textured surface, or a smooth surface? Of course you want the smooth surface. The friction made by the smooth surface might be 10 pounds, making you push up 100 pounds. The friction produced by a textured surface might be 20 pounds of friction, making you push up 110 pounds. BUT if you wanted to lower the box down a ramp, you would want the textured surface because the friction produced would be 20 pounds still, so you are lower a 70 pound box. So the friction produced would be the same lower and raising the something, it just works with you on the eccentric. Hope that makes since.


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## CowPimp (Mar 11, 2005)

I understand the concept of friction very well.  Friction is strictly an opposing force whose quantity is equal to the normal force multiploed by the coefficient of friction between the two rigid bodies.  

I should've phrased my statement better.  It came out wrong.  My speculation was that friction durring eccentric movement is actually causing more microtrauma to the muscle.

I was just thinking that perhaps muscle friction has something to do with the fact that eccentric motion is more effective at inducing hypertrophy.


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## ihateschoolmt (Mar 12, 2005)

CowPimp said:
			
		

> I should've phrased my statement better. It came out wrong. My speculation was that friction durring eccentric movement is actually causing more microtrauma to the muscle.
> 
> I was just thinking that perhaps muscle friction has something to do with the fact that eccentric motion is more effective at inducing hypertrophy.


 That's interesting, I've never heard that before. Any studies backing that up?


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## Cold Iron (Mar 12, 2005)

ihateschoolmt said:
			
		

> That's interesting, I've never heard that before. Any studies backing that up?




I've read this for years


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## ihateschoolmt (Mar 12, 2005)

Cold Iron said:
			
		

> I've read this for years


I'm still kind of new to working out.


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## SlimShady (Mar 12, 2005)

This thread is very interesting.  Does the amount of friction change, based on the amount of weight being lifted? Or is it a constant level of friction? 

 If someone relaxes their arm, you can easily move it. Would seem there is little to no friction during rest.


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## ihateschoolmt (Mar 12, 2005)

SlimShady said:
			
		

> This thread is very interesting. Does the amount of friction change, based on the amount of weight being lifted? Or is it a constant level of friction?


 Friction is strictly an opposing force whose quantity is equal to the normal force multiplied by the coefficient of friction between the two rigid bodies.


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## SlimShady (Mar 12, 2005)

ihateschoolmt said:
			
		

> Friction is strictly an opposing force whose quantity is equal to the normal force multiplied by the coefficient of friction between the two rigid bodies.


 Ok, yup, that's the def of friction... but the question still remains - does muscular friction increase as heavier weights are lifted? Any thoughts?


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## reg56 (Mar 12, 2005)

CowPimp said:
			
		

> My speculation was that friction durring eccentric movement is actually causing more microtrauma to the muscle.


 This is indeed true because the eccentric phase promotes blood flow to the specific muscle being trained. Microtrauma helps in building your muscles even stronger during your rest days, so make sure you do some slow, painful negatives.


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## P-funk (Mar 12, 2005)

reg56 said:
			
		

> This is indeed true because the eccentric phase promotes blood flow to the specific muscle being trained. Microtrauma helps in building your muscles even stronger during your rest days, so make sure you do some slow, painful negatives.




I don't understand what all the discussion is about??  I thought this was a known fact, just common knowledge.


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## reg56 (Mar 12, 2005)

Just thought I'd further explain what cowpimp originally said.  I know the majority of people already know this, but I figured newcomers would benefit from it.


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## ihateschoolmt (Mar 12, 2005)

SlimShady said:
			
		

> Ok, yup, that's the def of friction... but the question still remains - does muscular friction increase as heavier weights are lifted? Any thoughts?


 Yes. friction equal to the normal force *(the heavier the weight the bigger this number)*multiplied by the coefficient of friction between the two rigid bodies. So say you are lifting 50 pounds and say the coefficient is 0.15. The equation would be 50x0.15 thats 7.5 pounds of friction. Now say you are lifting 100 pounds. The equation is 100x0.15, that is 15 pounds of friction. (I think that's what it means at least).


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## Duncans Donuts (Mar 12, 2005)

P-funk said:
			
		

> I don't understand what all the discussion is about??  I thought this was a known fact, just common knowledge.



No way, i doubt most people even consider this stuff..


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## P-funk (Mar 12, 2005)

Duncans Donuts said:
			
		

> No way




yeah, i guess not.  

I always just assumed that everyone knew that.


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## Duncans Donuts (Mar 12, 2005)

Most people avoid physics


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## P-funk (Mar 12, 2005)

Duncans Donuts said:
			
		

> Most people avoid physics




well, it is hard to get excited about phyiscs.  For me at least.


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## CowPimp (Mar 12, 2005)

ihateschoolmt said:
			
		

> Yes. friction equal to the normal force *(the heavier the weight the bigger this number)*multiplied by the coefficient of friction between the two rigid bodies. So say you are lifting 50 pounds and say the coefficient is 0.15. The equation would be 50x0.15 thats 7.5 pounds of friction. Now say you are lifting 100 pounds. The equation is 100x0.15, that is 15 pounds of friction. (I think that's what it means at least).



Yeah, you're on the right track.  Although, figuring out the internal friction in a muscle is far more complicated than that.  For an object sitting on a flat surface, the normal force is equal to the weight.  However, that's about the only time this simple case is true.


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## ihateschoolmt (Mar 12, 2005)

CowPimp said:
			
		

> Although, figuring out the internal friction in a muscle is far more complicated than that.


I know, I was just using that as an example. What is the real equation to figure out the coefficient of friction?


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## reg56 (Mar 12, 2005)

Physics major DD?


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## P-funk (Mar 12, 2005)

reg56 said:
			
		

> Physics major DD?




LOL, he is not even in college yet!!  he is just a smart guy that is ahead of his time.


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## reg56 (Mar 12, 2005)

...holy.....shit.

   Smart, jacked, and a middle linebacker?

   What else can you do? lol


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## P-funk (Mar 12, 2005)

you can say that again!


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## chris mason (Mar 13, 2005)

Well, as you know DD, Jones and Darden theorize that intramuscular friction during contraction may be responsible for the fact that you can lower more than you can lift.  This friction would theoretically create a situation where less force production is necessary during the eccentric contraction due to the fact that friction is working in your favor when lowering the weight.  In other words, the force from friction is additive to the force being produced by your musculature and therefore less force from the muscles is necessary to perform the movement during the eccentric phase.  

Of course, the eccentric phase requires less force anyway because you are now only required to produce enough force to allow gravity to do its thing while still maintaining control.  In other words, to lift the weight you have to produce enough force to overcome gravity and make the load move in the opposite direction.  When lowering a load you have to produce only enough force to control the descent while gravity takes its toll.  

Now, as to damage induced by friction and all of these other ideas that is pure conjecture.  In addition, the idea of friction having any significant effect is also pure conjecture as the amount of friction that occurs may be so minute as to have no real effect.


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## DeadBolt (Mar 13, 2005)

CowPimp said:
			
		

> I should've phrased my statement better.  It came out wrong.  My speculation was that friction durring eccentric movement is actually causing more microtrauma to the muscle.


The reason the ecentric phase causes more microtrauma to the cell all breaks down and comes to the sarcomeres...which include the myosin and actine.  The crossbridges attach to these two together and as you perform the concentric portion of the movement they slide together (sliding filliment theory).  They are at a very stable point here....as you move into the ecentric phase the same amount of force is being applied to these cross bridges but they are being split apart which means less cross bridges are forced to hold the same amount of weight as before. 



			
				SlimShady said:
			
		

> This thread is very interesting.  Does the amount of friction change, based on the amount of weight being lifted? Or is it a constant level of friction?
> 
> If someone relaxes their arm, you can easily move it. Would seem there is little to no friction during rest.


Your body produces the amount of force needed....muscles are always working when your arm is at rest just to keep it in place.  At all times muscles are working its just a matter of how much.  So your example of a limp arm on a table for instance...there are muscles and riction in place but it is a minimal amount as compared to having to lift a heavy object of some sort.


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## chris mason (Mar 13, 2005)

Deadbolt, what are you talking about? Where are you getting your information from?


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## CowPimp (Mar 13, 2005)

ihateschoolmt said:
			
		

> I know, I was just using that as an example. What is the real equation to figure out the coefficient of friction?



First you would have to figure out the normal force.  

Then, you would have to figure out the actual force of the kinetic friction.  Determine the sum of all the forces by using the old sum of the forces = mass of the object x acceleration of the object equation.  Direction of the forces is VERY important.  From the sum of all the forces, you must subtract out every individual force from this number, except for the force of kinetic friction.  The end result will be the force of the kinetic friction. 

Divide the magnitude of the force of friction by the magnitude of the normal force.

Depending on the problem, this may actually involve working out dozens of separate equations.


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## CowPimp (Mar 13, 2005)

chris mason said:
			
		

> Now, as to damage induced by friction and all of these other ideas that is pure conjecture.  In addition, the idea of friction having any significant effect is also pure conjecture as the amount of friction that occurs may be so minute as to have no real effect.



True true.  That's why I was merely speculating.  I was curious if it did have any effect.


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## DeadBolt (Mar 13, 2005)

chris mason said:
			
		

> Deadbolt, what are you talking about? Where are you getting your information from?


I answered a question....and my source is my schooling.


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## Duncans Donuts (Mar 14, 2005)

> Your body produces the amount of force needed....muscles are always working when your arm is at rest just to keep it in place. At all times muscles are working its just a matter of how much. So your example of a limp arm on a table for instance...there are muscles and riction in place but it is a minimal amount as compared to having to lift a heavy object of some sort.



I don't understand this...if such were the case, a dead human being's muscles must be working in order to keep the arm placement, even at rest.  This is simply untrue..



> The reason the ecentric phase causes more microtrauma to the cell all breaks down and comes to the sarcomeres...which include the myosin and actine. The crossbridges attach to these two together and as you perform the concentric portion of the movement they slide together (sliding filliment theory). They are at a very stable point here....as you move into the ecentric phase the same amount of force is being applied to these cross bridges but they are being split apart which means less cross bridges are forced to hold the same amount of weight as before.



I don't understand this.  What schooling taught you this?  I haven't seen any specific evidence that the eccentric phase causes more microtrauma, though I believe something to that effect.  I think you need to elaborate a bit on the second quote I posted, becaues I'm not sure exactly what you are implying...


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## DeadBolt (Mar 14, 2005)

Duncans Donuts said:
			
		

> I don't understand this.  What schooling taught you this?  I haven't seen any specific evidence that the eccentric phase causes more microtrauma, though I believe something to that effect.  I think you need to elaborate a bit on the second quote I posted, becaues I'm not sure exactly what you are implying...


The reason you cause more hypertrophy during the ecentric phase is b/c you are being forced to produce the same amount of force while you are using less concentrared muscle fibers.

http://bio.winona.msus.edu/berg/ANIMTNS/SlidFila.htm

Here is what I am talking about...at full contraction the muscle fibers are as tight as they can be....but once you move into the ecentric phase of the movement they stretch out but the whole time having to hold the same amount of weight.

And my first quote I was refering to isometric force....at all times while living your body has to produce force or else you would fall to the floor like warm jello.  The muscles are what hold us upright and make us function.


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## SlimShady (Mar 14, 2005)

DeadBolt said:
			
		

> And my first quote I was refering to isometric force....at all times while living your body has to produce force or else you would fall to the floor like warm jello. The muscles are what hold us upright and make us function.


 But what if you are laying down and at rest?... how are your muscles at work? Like in the example of simply grabbing the arm of a person who is asleep. It is very easy to move the arm.


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## Dale Mabry (Mar 14, 2005)

Duncans Donuts said:
			
		

> I don't understand this.  What schooling taught you this?  I haven't seen any specific evidence that the eccentric phase causes more microtrauma, though I believe something to that effect.  I think you need to elaborate a bit on the second quote I posted, becaues I'm not sure exactly what you are implying...



Here is a snippit for ya...

DOMS is often precipitated predominantly by eccentric exercise, such as downhill running, plyometrics, and resistance training. In their review, Connolly et al. (2003) explain that the injury itself is a result of eccentric exercise, causing damage to the muscle cell membrane, which sets off an inflammatory response. This inflammatory response leads to the formation of metabolic waste products, which act as a chemical stimulus to the nerve endings that directly cause a sensation of pain. These metabolic waste products also increase vascular permeability and attract neutrophils (a type of white blood cell) to the site of injury. Once at the site of injury, neutrophils generate free radicals (molecules with unshared electrons), which can further damage the cell membrane. Swelling is also a common occurrence at the site of membrane injury, and can lead to additional sensations of pain. Connolly et al. also note the importance of differentiating DOMS from other injuries such as muscle strains. This difference is important to appreciate because when muscle strain is sustained from vigorous exercise, particularly eccentric exercise, it can severely worsen the injury. In contrast, in a muscle that is experiencing DOMS, continued eccentric exercise is still possible without further muscle damage. When dealing with DOMS it is important to differentiate it from muscle strains, recognizing that continued exercise is still possible with DOMS, but not with muscle strain.



We know DOMS is greater in eccentric movements, now if only the exact 
mechanisms were known...

I have no idea where this came from, I closed the tabe before I copied the URL.


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## Dale Mabry (Mar 14, 2005)

SlimShady said:
			
		

> But what if you are laying down and at rest?... how are your muscles at work? Like in the example of simply grabbing the arm of a person who is asleep. It is very easy to move the arm.



Easy yes, effortless no.


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## chris mason (Mar 15, 2005)

Dale Mabry said:
			
		

> Here is a snippit for ya...
> 
> DOMS is often precipitated predominantly by eccentric exercise, such as downhill running, plyometrics, and resistance training. In their review, Connolly et al. (2003) explain that the injury itself is a result of eccentric exercise, causing damage to the muscle cell membrane, which sets off an inflammatory response. This inflammatory response leads to the formation of metabolic waste products, which act as a chemical stimulus to the nerve endings that directly cause a sensation of pain. These metabolic waste products also increase vascular permeability and attract neutrophils (a type of white blood cell) to the site of injury. Once at the site of injury, neutrophils generate free radicals (molecules with unshared electrons), which can further damage the cell membrane. Swelling is also a common occurrence at the site of membrane injury, and can lead to additional sensations of pain. Connolly et al. also note the importance of differentiating DOMS from other injuries such as muscle strains. This difference is important to appreciate because when muscle strain is sustained from vigorous exercise, particularly eccentric exercise, it can severely worsen the injury. In contrast, in a muscle that is experiencing DOMS, continued eccentric exercise is still possible without further muscle damage. When dealing with DOMS it is important to differentiate it from muscle strains, recognizing that continued exercise is still possible with DOMS, but not with muscle strain.
> 
> ...


 
This is the problem with the internet and bodybuilding boards.  The above you have quoted is ONE theory on DOMS.  It may or may not be accurate and should not be taken as a statement of fact.


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## chris mason (Mar 15, 2005)

DeadBolt said:
			
		

> The reason you cause more hypertrophy during the ecentric phase is b/c you are being forced to produce the same amount of force while you are using less concentrared muscle fibers.
> 
> http://bio.winona.msus.edu/berg/ANIMTNS/SlidFila.htm
> 
> Here is what I am talking about...at full contraction the muscle fibers are as tight as they can be....but once you move into the ecentric phase of the movement they stretch out but the whole time having to hold the same amount of weight.


What you are saying above makes no sense.

What you are referring to with respect to the muscles when standing is called MUSCLE TONE.  Muscle tone is defined as low levels of contractile activity in relaxed muscles that keep them healthy and ready to respond to stimulation.  Muscle tone is especially important with respect to the tendons that cross joints.  The muscle tone keeps the tendons tight thus stabilizing the joint.  This information is from *Human Anatomy and Physiology *by Elaine Marieb.


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## SlimShady (Mar 15, 2005)

Dale Mabry said:
			
		

> Easy yes, effortless no.


 Still, I would say it is virtually effortless. Most of the resistance seems to be due to the weight of the limb, and not to any internal friction. But what do I know..


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## Dale Mabry (Mar 15, 2005)

chris mason said:
			
		

> This is the problem with the internet and bodybuilding boards.  The above you have quoted is ONE theory on DOMS.  It may or may not be accurate and should not be taken as a statement of fact.



1)You are correct, there are many theories out there

2)Most of these theories have no research backing and have been disproven, this one is backed by lab tests.

Some Sources

http://www.naturalphysiques.com/cms/index.php?itemid=142

http://www.drlenkravitz.com/Articles/doms.html


I am not saying this theory is 100% right, but the sliding filament theory of muscular contraction has not been proven either, yet most consider it as fact.  Without theory there is no discovery.


So what is your theory?


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## Duncans Donuts (Mar 15, 2005)

If it hasn't been tested, it's technically not a theory, is it?  Wouldn't it be a hypothesis?  The references who have tested their hypothesis seem to have a valid, logical theory, though.


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## Dale Mabry (Mar 15, 2005)

Duncans Donuts said:
			
		

> If it hasn't been tested, it's technically not a theory, is it?  Wouldn't it be a hypothesis?



Sort of...You can look at someone else's work and as long as you and other's come to the same conclusion it would be considered a theory even though a study was not done on the specific phenomena you are talking about.  One person's take on an event is a hypothesis.  Really the only difference is whether a significant portion of the scientific community finds credence in your finding.

If you were to look in a textbook you would find your definition, but once you get into the real world the definitions become fuzzy.


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## DeadBolt (Mar 15, 2005)

chris mason said:
			
		

> What you are saying above makes no sense.
> 
> What you are referring to with respect to the muscles when standing is called MUSCLE TONE.  Muscle tone is defined as low levels of contractile activity in relaxed muscles that keep them healthy and ready to respond to stimulation.  Muscle tone is especially important with respect to the tendons that cross joints.  The muscle tone keeps the tendons tight thus stabilizing the joint.  This information is from *Human Anatomy and Physiology *by Elaine Marieb.


Actually it wasn't from elaine marieb...it was from my prof @ my college.  He has written several books in this field but don't know the names off hand.


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## chris mason (Mar 16, 2005)

DeadBolt said:
			
		

> Actually it wasn't from elaine marieb...it was from my prof @ my college. He has written several books in this field but don't know the names off hand.


You misunderstand, the information I provided was gotten from Elaine's book.


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## chris mason (Mar 16, 2005)

Dale Mabry said:
			
		

> 1)You are correct, there are many theories out there
> 
> 2)Most of these theories have no research backing and have been disproven, this one is backed by lab tests.
> 
> ...


You have misunderstood my point.  To be frank, the theory presented makes sense to me (I didn't have a problem with the information presented).  My point was that people often quote theory as though it were fact on the internet. 

In addition, they quote or reference studies and assume that is the be all/end all.


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## Dale Mabry (Mar 16, 2005)

chris mason said:
			
		

> You have misunderstood my point.  To be frank, the theory presented makes sense to me (I didn't have a problem with the information presented).  My point was that people often quote theory as though it were fact on the internet.
> 
> In addition, they quote or reference studies and assume that is the be all/end all.




Oh, I understood what you were saying.  I hate the internet because sometimes it can seem you are being standoff-ish when you are not.  I wanted to know which theory do you personally subscribe to, I wasn't being a smartass.  Dumbass yes, smartass no.


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## DeadBolt (Mar 16, 2005)

chris mason said:
			
		

> You misunderstand, the information I provided was gotten from Elaine's book.


I apologize...I re read it and understand now.

And yes I was refering to muscle tone...but only in that one instance.  In refrence to the ecentric phase I feel my answer was sufficient.


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