 
   |
By Eric Troy, Ground Up Strength
<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <title>Above Article Ads</title> </head> <body> <!-- 2 This is the HTML section of the badge --> <script type="text/javascript"><!-- google_ad_client = "pub-1717216010164069"; /* 300x250, created 4/7/09 */ google_ad_slot = "4278139465"; google_ad_width = 300; google_ad_height = 250; //--> </script> <script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js"> </script> <!-- Badge ends --> </body> </html>
A brief explanation…
The purpose of this explanation is to help the reader understand, in simple terms, the concept for open kinetic chain versus closed kinetic chain. As such the complexities of the kinetic chain concept in it's entirety are not discussed, for to understand this concept completely would require an entire tome as it involves more than just the bones of the body and their joint linkages but also encompasses the soft tissues such as muscle, tendon, ligament, and the nervous system.
For our purposes, here, however, we can view the body as simply a collection of bony parts linked by a series of joints. Thus a chain.
Imagine a chain that is spread out without either one of it's ends being joined to any other object or to each other. Hence the chain is open. You will see that either end or extremity of the chain can be manipulated without much effect on any other link. But if you attach one or both ends of the chain so that it is closed it is difficult to move any one link in the chain without movement in other links of the chain.
Some writers will assert that it is impossible to effect the movement of one link in a closed chain without a lot of movement in other adjoining links but I do not think this is entirely accurate, as will be discussed later.
The "distal end" is a part of the body that is furthest away from the trunk or middle. So, for instance, the hand is the distal end of the upper extremities. If you press a dumbbell or barbell the kinetic chain is open. In other words the hands are free to move freely in space and not "attached" to something immovable, such as the floor, or wall. So, the bench press or overhead press is an open chain exercise.1 Any one joint can be moved without other joints being affected significantly. You can do a wrist curl without moving your elbow or shoulder much (the proximal joints or segments). The same goes for a curl or extension, etc…This does NOT mean that there is never movement in adjoining joints in open chain exercises, it simply means that it is possible for movement to occur at any one joint without movement in the others.
But in the case of closed chain movements, where the distal end is stationary, it becomes much more difficult to move any one joint without a compensatory movement along the entire chain. Compare the press to a natural pushup. Movement in one joint cannot occur without movement in the others.
So, muscle groups are more easily isolated during open–kinetic chain exercises, whereas there is more movement of proximal segments in closed chain movements and therefore more co-contraction.
<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <title>Above Article Ads</title> </head> <body> <body bgcolor="#E6EFF6"> <script src="http://tag.contextweb.com/TagPublish/getjs.aspx?action=VIEWAD&cwrun=200&cwadformat=120X600&cwpid=514880&cwwidth=120&cwheight=600&cwpnet=1&cwtagid=66369"></script> <!-- Badge ends --> </body> </html>
This is the general idea. However, as I stated at the beginning movement is complex and there do exist many gray areas between defining the concept of open versus closed in body movements. After all, the human body is a bit more complex than a simple metal chain. In the case of certain movements, and especially with machines, there can exist exercises that could be described as "partially" closed or open.
The difference, in my opinion, has to do with the predictability of subsequent joint movement in certain exercises. With a barbell back squat, (closed chain movement) for instance, properly performed, it is very easy to predict the movement of body segments based on body geometries, bar position, stance width, etc. But exchange that barbell, where the weight's movement is not held to a fixed plane, and replace it with a smith machine squat, and you will see that the concept of open versus closed becomes much less clear-cut. The bar in a smith machine is forced to travel in a fixed plane of motion and thus the subsequent movements of the body's segments are not easily predictable. Although a smith machine squat is, upon first glance, a closed chain movement…it resides in the gray area I mentioned above. During a squat the body needs to maintain the center of mass, which has been moved upward from the middle by the addition of the barbell. When a fixed plane of motion is introduced this natural movement can no longer occur.
A popular alternate definition of these terms is basically that "open chain" means the force applied by the body is great enough to overcome the resistance while with "closed chain movements" the force is not great enough to overcome the resistance. I find this to be a nonsense explanation which can create a lot of confusion. The idea is that, with a squat, the force is applied to the floor but, of course you can't move the floor. With bench press the force is applied to the bar which moves….
Such a nice, black and white explanation would be quite handy. Too bad it makes no real sense. With either movement, body segments move and that is what is important. The "resistance" in squat is NOT the floor. The floor is simply the surface which "closes" the distal end. The resistance that is being moved is still the bar. Remember..the distal end is the extremity and this is what determines, in simple terms whether a movement is closed or open. But it does not determine, necessarily, where the mass sought to be moved rests. The explanation works better when you think of running where you apply resistance to the ground which moves the body.
It's hard to tell why this kind of explanation exists but if I could guess, it would be to help explain skill transfer in simpler terms. But this is a case of the centipede and it's many legs.
To put this explanation to rest one need only consider an overhead squat.
Muscle groups may be isolated during open–kinetic chain exercises, and more co-contraction of various muscle groups occurs during closed–kinetic chain exercises.
Since the body is not merely a collection of bony links all movement cannot be explained or predicted by this model. Keep in mind that a model such as this is a simplified version of a complex system and models only serve to help us envision and understand these systems intuitively. The body could also be viewed as a collection of possible levers. It is much more difficult to view the body this way than as a simple chain! Especially since the type of lever for a given joint and muscle changes as a result of how the each part is arranged in relation to the other, and again, when the distal end is in fixed contact a new lever system is created.
- Eric Troy
<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <title>Above Article Ads</title> </head> <body> <!-- 2 This is the HTML section of the badge --> <script src="http://tag.contextweb.com/TagPublish/getjs.aspx?action=VIEWAD&cwrun=200&cwadformat=728X90&cwpid=514880&cwwidth=728&cwheight=90&cwpnet=1&cwtagid=54612"></script> <!-- Badge ends --> </body> </html>
