EDITOR'S NOTE: Due to the current fitness industry debate about the validity of the Open and Closed chain training model, we at PTontheNet.com have tried to offer multiple perspectives so that trainers can assess all the facts and make informed decisions to suit their needs. The following physiological exploration by Mel Siff provides an interesting counterpoint to the article titled "Open and Closed Chain" by accomplished physiotherapist Suzi Nevell. Enjoy both reads and let us know what you think!
It is now fashionable especially in physiotherapy circles to refer to open and closed chain exercise. The term open chain exercise (or, open kinetic chain - OKC - exercise) is applied commonly to actions in which the end of a limb is free to move in space, whereas closed chain exercise (or, closed kinetic chain - CKC - exercise) refers to any exercise where the limb is restrained against an immobile surface such as the ground. Thus a seated 'leg extension' is open chain (OKC), whereas a squat is closed chain (CKC).
What then about a seated leg press, where the foot is pressed against a restraining surface? Presumably this is purely open chain, because the end of the extremity is free to move. What then of a 'hip sled' or inclined machine squat exercise? The action is virtually the reverse of the seated leg press, only the body is moving instead of the legs. We must not forget that in a leg extension exercise, the shin makes contact with a bar. In competitive rowing the athlete thrusts powerfully with the legs and slides backwards and forwards during the stroke. Would we call this open-closed chain exercise? Presumably walking, running, jumping and aerobic stepping are also mixed open-closed chain exercises. This artificial classification of exercises is not quite as clearcut as the authorities would like you to believe, nor is it as useful as published work often tends to suggest.
In recent times, frequent theoretical distinction has been made between 'closed chain' and 'open chain' exercises, especially among physical therapists who may have to choose between "closed kinetic chain" rehabilitation with squats or "open kinetic chain" rehabilitation on a leg extension device.
The Original Definition
What exactly do these terms mean? According to their creator, Dr Steindler: "We designate an open kinetic chain a combination in which the terminal joint is free..... A closed kinetic chain, on the other hand, is one in which the terminal joint meets with some considerable external resistance which prohibits or restrains its free motion." (Kinesiology of the Human Body under Normal and Pathological Conditions, Springfield, 1955). Immediately, this dismisses the common notion that closed chain exercises are those in which the distal extremities are fixed against an immovable surface. Steindler's definition actually implies that leg extensions against a near maximal or maximal load should be classified as a closed chain exercise, a deduction that would surprise most therapists.
This apparently meticulous definition (and there are others, each with their own nuances of meaning - see the appropriate textbook) seems to package exercises very conveniently and usefully, but all definitions pose problems and this one is no exception.
Application of the Original Definition
Let us begin by examining just how neatly and exclusively this definition works. It clearly seems to classify a free standing squat with a bar on the shoulders as a closed chain exercise and a seated knee extension as an open chain event. What about a reclining leg press, where the feet are firmly fixed against a plate carrying a load which thus can be pushed away from the body? Is this closed chain because the distal extremity is pressing against a surface, thereby activating the positive supportive and extensor reflexes? Or is it open chain because the distal extremity is free to move? If we are to apply Steindler's original definitions, then openness or closedness are a function of the degree of loading, not just the tendency of the distal extremities to move or remain fixed.
In a similar vein, the push-up off the floor would appear to be closed chain exercise and the bench press would seem to be open chain. A wrestler engaged in a pushing struggle with both of his hands pressing firmly against his opponent's hands would be in a situation in which his hands sometimes are rigidly fixed against a surface and sometimes in active motion. Would he be indulging in closed or open chain exercise or both simultaneously?
Common Human Activities
Let us examine the common acts of walking and running. Do they constitute open or closed chain exercise or some sort of cyclical combination of both? It would appear that when one foot is on the ground the action is closed chain, but when the lower extremity is moving in the air it is open chain. This brings us to exercise on various ergometers and cyclical machines. Is treadmill running closed or open chain? Is cycling on a fixed cycle or a road cycle the same and is it open or closed chain in nature?
Are we not being shown in these examples that, in many daily and sporting activities, parts of the body are executing open chain movements, while other parts are executing closed chain exercises -- and that this sort of integrated alternation of types of action is essential for all efficient and safe human movement? Also of great importance is the fact that actions of muscles in the lower extremities can profoundly affect movement in other parts or limbs of the body, even though the muscles of the lower extremities have no direct structure connection with those other parts of the body (I discussed this in my previous article: "So This is How the Muscles Work!").
What about swimming? What then about tethered swimming, where the swimmer is restrained from moving by being attached by rope to the end of the pool? This brings us to another subtle issue. In a medium such as water, the extremities (and all other parts of the body) are acting against a fluid which is highly deformable and 'unfixed', a point which makes us think a little more carefully about the mechanical nature of the surface against which the extremities are pressing.
One particularly interesting aspect about swimming is that leisurely swimming produces much smaller resistance against the arms and legs, so that, according to Steindler’s original definition, that sort of swimming is open chain for all the extremities. Conversely, if one swims at full speed, the resistance to movement of the extremities becomes considerable, so that, classically, this type of swimming could be classified as "closed chain".
Suppose that the surface is not as rigid as the floor, but is deformable. This would bring us to the situation of trampolining and springboard diving. Are these activities open chain or closed chain? Are the lower extremity actions clearly closed chain while the feet are in contact with the stretched or deflected surface?
Analysis of Training Activities
Other important issues arise when we examine the dynamics of exercise. Let us consider the case of a seated knee extension exercise. Up to the point before the arm of the machine begins to move, the leg extensors are contracting isometrically until they are able to overcome the load. Thus, during the isometric or pre-stretching phase, the shin is restrained from moving. Does this imply that the exercise up to this point is closed chain, with a transition to open chain behaviour once movement begins? This issue concerns all so-called open chain movement against gravity or some form of resistance - there is always an isometric phase during which the distal extremity is prevented from moving by the external load!
Let us examine the ‘Olympic’ weightlifting movements of the Snatch and Clean & Jerk, in which the lifter starts with the bar on the platform and has to either snatch it overhead in one movement or thrust it overhead in two movements using a Clean to the shoulders and an explosive Jerk overhead.
Ostensibly, the lifter’s feet are planted firmly on the platform to supply a powerful base for the ensuing actions throughout the lifts. However, this is not necessarily the case, because a very large percentage of lifters extend during the pulling phase of both lifts and then lift their feet slightly in the air or slide them sideways into a slightly wider stance. In other words, for a brief instant, the movement of the lower extremities become open chain, while the pulling and pushing movements of the upper extremities always appear to be open chain during the ‘Olympic’ lifts.
Yet, according to Steindler’s original definition, a closed exercise may also be one in which "the terminal joint meets with some considerable external resistance which prohibits or restrains its free motion", so that the jerking action could quite legitimately be classified as "closed kinetic chain". Only if one changes Steindler’s original definition to exclude his categorisation of "closed" chain exercises being ones which are executed against considerable resistance can we be as rigid as some experts are on this issue. This, unfortunately, sounds a great deal like applying the so-called Procrustean Method, named after the legendary inn-keeper who cut off parts of the legs of any guests who complained that they were too tall for his beds.
What we do note in all of the cases mentioned is that many movements in daily life and sport involve the regular alternation of "openness" and "closedness" of the chains involved in the action and that strict classifications may be of some limited value in clinical situations, but not necessarily of any complex exercises in sport and daily life (as simple as walking and running). What also has to be emphasized is that the concept of "kinetic chains" may be applied only to situations where the isolated action of any given extremities is concerned. A noteworthy exception concerns all actions of the trunk. If we simply refer to this region of the body as some "link" in the whole kinetic chain, this is misleading and misrepresents other non-rigid body actions which the trunk can mediate. This means that exercises like sit-ups, crunches and wrestlers’ bridges are neither closed nor open, since all definitions of closed and open kinetic chains rely on the state of fixation of the extremities -- and the trunk has no discrete extremities. Sit-ups, crunches and any other similar trunk exercises are undefinable, according to the limited concept of closed and open chains. For this reason alone, the popular use of this concept of 'openness' or 'closedness' of bodily chains needs to be carefully reconsidered.
Let us also consider the sometimes disregarded method of loadless training often used by Russian athletes and by bodybuilders during their posing routines. In such cases the athlete strongly tenses the agonists and antagonists of a specific joint against one another, without any external load or without any external movement resulting (see Supertraining 2000 Ch 7).
The muscles simply 'compete' internally against one another to produce a powerful contraction. How exactly would one classify this type of exercise? It is neither open nor closed, since the extremities are not subjected to any external loading, even though they are experiencing considerable internal tension.
In other words, all movement would appear to be a succession of phases of open, closed or unclassifiable chain activity, especially of the trunk portion of whole body linked system. On the other hand, the entire concept of open and closed chain exercise may be regarded as trivial, useless, misleading and irrelevant! This would suggest that this type of classification should be discarded.
Which viewpoint is correct? Or is neither correct? Is there a better way of classifying exercises or is any such system redundant? Does this open vs closed chain system of classification have any scientific or practical merits whatsoever? Would the world of fitness and rehabilitation be any the poorer without it? Does it really play any essential or unique role in explaining human exercise or enhancing rehabilitation? Another categorisation of Closed vs Open Chain movements refers to the former as highly deterministic, fixed pattern movements and the latter as movements which are constantly varying and unrestrained in space.
Others derive their understanding of closedness and openness from their knowledge of linked mechanical systems in engineering and question both of the definitions referred to in this puzzle. Which is then the most appropriate definition? Which is the definition determined by tradition? Are we willing to apply the Proscrustean Method and change the details to suit our beliefs?
Is any one of these definitions of openness or closedness truly relevant in sports science, physiotherapy and sports training? There are some of us who may think otherwise.
- Siff M C Facts and Fallacies of Fitness 2002
- Siff M C Supertraining 2000
- Archives of the Supertraining forum at: http://groups.yahoo.com/group/Supertraining/