Evaluating the Claims Regarding “Open Chain” and “Closed Chain” Exercise
The concept of “Open Chain” and “Closed Chain” exercise has been around for some time now. It originated in the late 1800s and was more fully embraced in the mid 1900s. Today, there are a growing number of people – mostly in the Physical Therapy field, but also in mainstream fitness – who are preaching it. In general, the typical recommendations – as per its proponents – are that “Closed Chain” exercises are better (more productive and more safe) than are “Open Chain” exercises. This essay is intended to explore these recommendations, and evaluate their merit.
Closed Chain Exercises
A “Closed Chain” exercise is defined as an exercise that requires one’s feet or hands to be in a constant, fixed position – on the ground, a bench, a chin-up bar, dipping bars, etc.. Examples of this would include Squats, Push-Ups, Pull-Ups, Dips, etc. This type of exercise usually requires the use of one’s own body weight, as a minimum. Closed Chain exercises are often considered “compound” exercises, because they involve multiple joints and muscle groups working simultaneously. Because of this, proponents consider these exercises to be more “functional”. “Functional” is a term used to suggest that the benefit of an exercise is more “applicable” or “use-able” in day-to-day life.
Advocates of Closed Chain exercise explain that, when additional weight is added, it usually rests across the back of the shoulders or otherwise on the torso, and believe that it is, “much safer than the placing a load on the distal end of a limb” — as is usually the case during Open Chain exercise. (The “distal end” means the far end of the limb – farthest away from the operating joint… for example, at the ankle, when doing Leg Extensions.)
Open Chain Exercises
An “Open Chain” exercise is defined as an exercise where one’s feet or hands are not on a stable, fixed surface. Instead, they would be on a barbell, dumbbells, cable handles, or machine lever (like a Leg Extension) – moving through space. Examples of this include Supine (Flat Bench) Dumbbell Press, Triceps Pushdown with Cable, Dumbbell Biceps Curls, Leg Extensions, etc. One of the claims made by advocates of Closed Chain exercise, is that Open Chain exercises isolate a single muscle group and a single joint — and that isolation is not good. The example most often given is the Leg Extension, and the fact that it isolates the Quadriceps muscle, in the absence of Hamstring participation.
Proponents of this philosophy also claim that Closed Chain exercise produces “compressive forces” (also known as “parallel force”) – which are “good”, and that Open Chain exercises produce perpendicular forces (which they also refer to as “shearing forces”) – which are “bad”. They say that “compressive forces help stabilize the joint”, and that “perpendicular forces are unsafe because they displace the joints.” Below is the often-used graphic, typically used by proponents of Closed Chain exercise, used to “explain” the difference between “compressive force” and “shear force”. The figures below refer to the upper and lower leg bones (Femur and Tibia, respectively). The figure on the left symbolizes the forces of a “Squat” (exercise), and the figure on the right, symbolizes the forces of a Leg Extension Machine.
A Bit of Physics
Before we begin examining each of these claims, let us review some basic physics principles which will provide some insight as to the validity of these claims.
Three Factors That Determine “Load”
When we use resistance during exercise, the goal is to “load” a muscle with an opposing force, against which a muscle must work. Weight lifting (aka “resistance exercise” and “strength training”) RELIES on an opposing resistance, during exercise. Therefore, it is essential for us to understand how “loading a muscle” happens. In every resistance exercise we do, there are three factors that determine how much load a given muscle encounters. These include: the actual weight we’re using, the length of the lever that’s moving that weight (i.e., your forearm, your lower leg, etc.), and the position of that lever through the arc of an exercise (i.e., the resistance curve).
Obviously, this last one varies, depending on where, in the range of motion of an exercise, that lever (limb) is at any given moment in time. For example, when we do Standing Barbell Curls, our forearm travels through an arc, which “finds” the least resistance at the bottom and at the top of the movement, but the most resistance in the middle of the range of motion. This is further explained below.
1. The actual amount of weight: (bodyweight, exercise machine, pulley, or free weight – i.e., dumbbell or barbell).
2. The length of the lever: the “actual weight” one is lifting is magnified by a factor that is related to the length of the lever one is using to lift the weight. For example, when we do “Curls”, our forearm is the operating lever. The length of that lever is the distance between the insertion of the Biceps (on the forearm, very close to the elbow joint), and the weight in your hand. The longer the lever (the distance between the muscle insertion, and the actual weight), the greater the magnification of that weight, to the working muscle.
3. The degree of “perpendicular-ness”: the angle at which the operating lever interacts with the direction of resistance (i.e., the “resistance curve” explained fully below), determines the percentage of resistance that is loaded onto the working muscle.
(Note: There is also a 4th factor, called “mechanical advantage / disadvantage”, which involves the angle from which a muscle is pulling on a bone, but it’s not critical in the context of this analysis.)
The Resistance Curve
A lever that is parallel with direction of resistance is “neutral”. It provides zero load to its operating muscle. A lever that is perpendicular with the direction of resistance is maximally active. It provides 100% of the available resistance to its operating muscle. A lever that is in positions between parallel and perpendicular provides percentages of the available resistance that are between zero and 100. Let’s do a simple experiment, to illustrate this concept. Put your arm on a table top, so that your forearm is pointing straight up (vertically). Now put a weight in that hand.
What you’ll notice is that regardless of how much weight is in your hand, it does not require any force from your Biceps, as long as that forearm stays perfectly vertical. This vertical position is parallel with resistance (gravity) and is, therefore, NEUTRAL. This is the reason why light posts are vertical, as well as most support beams in building structures.
Now, allow your forearm to come almost all the way down, so that the dumbbell in your hand is a fraction of an inch away from touching the table. You’ll notice that holding this position requires considerable force on the part of your Biceps. This position is the “maximally active” position. It is where the lever (your forearm) and the direction of resistance (gravity) are perpendicular.
Every position in between, where your forearm is vertical and horizontal (neutral and maximally active), is percentages between zero and 100. Calculating the exact percentage, at each stage of the range of motion of an exercise, isn’t necessary. But knowing that “parallel with resistance” = zero load to the muscle, that “perpendicular with resistance” = maximum load to the muscle, and that every angle in between is a percentage thereof, is important.
Let’s identify each of the claims made by the proponents of Closed Chain exercise, and then evaluate them one by one.
1. Closed Chain exercises create “compressive forces”. (These are forces that are parallel with our limbs, and therefore “compress” / “stabilize” the joints)
2. Open Chain exercises create “perpendicular forces”. (These are forces that are perpendicular with our limbs, and therefore “shear” / separate the joints.)
3. Closed Chain exercises are “compound” movements – requiring a group of muscles to work together, at the same time. This results in a more “functional” benefit, because it encourages muscles to synchronize the way they do in
4. Open Chain exercises are often “isolated” exercises – forcing an individual muscle to work without the cooperation of other muscles. This fails to “imitate life”, and is therefore not “functional” (not as beneficial and more risky).
5. Placing resistance at the “distal” (long) end of a limb is dangerous, because it magnifies the resistance too much. The example most often used is the placement of the lever-arm-pad of the Leg Extension machine, against the ankle.
6. Closed Chain / Compound exercises “save time”, as compared with doing Open Chain / Isolation exercises, because they work multiple muscles at one time.
Arguments Against the Claims
In the starting position of a Squat, the upper and lower leg are both parallel with gravity. This parallel force is described by “Closed Chain” proponents as “compressive force”, and they claim this helps “stabilize the knee” (pushing the upper and lower leg TOWARD each other). However, levers that are parallel with resistance are NEUTRAL – meaning that they present no load whatsoever to the muscles which operate those limbs. Of course, this would defeat the purpose of exercise. But a “Squat” is not just a person standing there, with their legs straight. That’s only the starting position, and it provides no load, and therefore no benefit, to the Quadriceps or the Glutes.
Once the person descends into the “Squatting” position, the upper and lower leg bones (Femur and Tibia) are no longer parallel with resistance (see figure below). This means two things: the so-called “compressive” force is progressively converted into perpendicular force, and the exercise has THEN begun loading the muscles involved. This “loading of the muscles” is a direct result of the bones (Femur and Tibia) moving into varying degrees of “perpendicular-ness” with gravity.
Yes, that is correct – the very thing “Closed Chain” proponents have deemed as “dangerous” (i.e., perpendicular forces) are what makes exercise useful. Without perpendicular forces, exercise would be USELESS.
Further, the claim that Open Chain exercises produce perpendicular forces, while Closed Chain exercises produce compressive (i.e. parallel) force, is incorrect. All exercises – Open Chain and Closed Chain – produce some degree of perpendicular force. All exercises have at least one lever (limb) which passes through a perpendicular (or semi-perpendicular) position with resistance. Perpendicular forces are not unique to Open Chain exercises. Push-Ups (a Closed Chain exercise) produce a perpendicular force on the upper arm. Are this person’s upper arms (below) not perpendicular to gravity? (they will be more so, once he stops smiling for the camera and goes a bit lower).
The same is true with Pull-Ups (another Closed Chain exercise). Are this person’s upper arms (photo below) not perpendicular with gravity? Of course they are.
The same is also true with “Sissy Squats” (another Closed Chain exercise). As you can clearly see (photo below), the Tibia (as the operating lever for the Quads) is nearly perpendicular with gravity.
Proponents of Closed Chain exercise seem to be most opposed to perpendicular forces as they relate to the legs. “Don’t let the knees go over the toes, when doing Squats”, is the typical advice. The rationale for preventing the knees from going over the toes, is that it would cause the lower leg to enter a somewhat (or “excessively”) perpendicular position to gravity. However – again – keeping the lower leg parallel with gravity would cause it to be a neutral lever, thereby providing little or not resistance at all, to the Quadriceps. Their primary concern with a perpendicular force acting upon the lower leg, is based on their mistaken belief that it would cause a “shearing” effect on the knee. However, this is baseless, and will be further explained and demonstrated below.
For What Purpose?
Advocates of Closed Chain exercise claim that Closed Chain exercises are “compound” movements (multi-joint /multi-muscle), and are therefore more “functional” – suggesting that they produce more benefit and have less risk of injury. They further claim that Open Chain exercises are “not functional”, because they are usually “isolation” movements. In fact, there are numerous Open Chain exercises that are “compound” movements. “Compound” exercises are not ONLY Closed Chain. Bench Press is a compound exercise, even though it is (so called) Open Chain. Bench Press works many of the same muscles that are used during Push-Ups (a Closed Chain exercise), including the Pectorals, Anterior Deltoids, Triceps, etc.. It’s true that Bench Press does not engage the abs, hip flexors and quads, but it does allow for more variation in resistance, which provides increased benefit and reduced risk to the muscles that are involved.
Standing Barbell Curls engage the Lower Back (erector spinae), the Glutes and the hamstrings – muscles which allow the person to stay upright while their front loaded upper body is being pulled forward. Yet, proponents of this theory would consider the Standing Barbell Curl, an “isolation exercise”. Standing Barbell Curls also involve the Trapezius. Thus, it is almost as much a “compound” exercise as are Push-Ups. But more importantly, one needs to ask “functional for what”? Making the broad claim that compound exercise are more “functional” for everyone, regardless of their goals and lifestyles, is misguided. Yes, for people who participate in sports, or in strenuous activities that resemble some of the compound lifts, they would be helpful. But for the person who simply wants more strength for everyday activities, more well-developed muscles, less body fat, better health, to enjoy their workouts, and to use a resistance level (i.e., weight) that is within their physical and psychological limits, isolation exercises are very good.
I’ve been weight training intensely for the past 38 years. I’ve used a wide variety of exercises, most of which would be considered “Open Chain” or “isolation” exercises. I’ve never been injured while exercising, and I’m perfectly “functional” for the active lifestyle I maintain. I’m flexible, athletic, coordinated, and strong enough for my goals – plus, I’ve won many physique competitions. Is that not “functional” enough? It’s literally impossible to see an obvious difference, in terms of day-to-day function, between those who have done compound exercises, and those who have done isolation exercises. I simply have not seen any empirical evidence to support the assertion that isolation exercises result in injury, nor that their benefits are not functional enough for day-to-day activities and sports. The idea of “functional” exercise is mostly theoretical. It is not manifested in reality.
There is also the issue of adherence to exercise, that these proponents seem to ignore. Bodyweight exercises are extremely difficult for the average person. Most lay people cannot do 20 Chin-Ups, 20 Push-Ups or 20 Parallel Bar Dips, very easily. And this defeats the purpose to a great degree. People often struggle to do 8 or 10 repetitions, use bad form, and hate the experience. And rightly so. Everyone has a different bodyweight, and a different strength level. Ironically, heavier people usually have less strength (due to inactivity), and should be using LESS weight than their lighter bodyweight counterparts – not more weight.
There is an unreasonable expectation that “everyone should be able to do bodyweight exercises”, and when people fail to do so, or they hate the process, they feel dejected and often quit exercising entirely. That is generally not the case when people use more moderate, “Open Chain” exercises, and a resistance level that is within their physical and psychological limits. Feeling successful during exercise is critically important, because it plays a role in one’s ability to continue without being discouraged.
Distal Placement of Resistance
Proponents of Closed Chain exercise would have us believe that placing a resistance at the “distal end” of a lever is “dangerous”. The rationale they use is that it “magnifies the resistance too much”, and therefore poses a risk to the joint. The example most often used is the placement of resistance at the ankle, while using a Leg Extension machine. The first reason why this assertion is incorrect, is that when we do Squats, the “resistance” is placed even more distally on the lever – at the foot. There is a greater distance between the insertion of the Patella tendon, and the foot – than there is between the insertion of the Patella tendon, and the ankle.
Take a look at the “Sissy Squat” photo shown above. You’ll see that although that exercise is considered “Closed Chain”, it uses a lever that is (technically) longer than that which is used during a Leg Extension machine. But here’s the real crux of the argument: people select a weight for an exercise, based on what they can handle.
In other words, whether a person uses 50 pounds placed at the end of a 12-inch lever (the approximate length of the lower leg), or 100 pounds placed half-way down that same lever – it’s going to feel the same to the user. The length of the lever determines magnification – yes. But the CHOICE a person makes about which weight he / she will use includes the magnification factor. A distal placement of a weight feels heavier ( is magnified more ) to the user, and so a lesser weight is selected – automatically.
Perpendicular VS. Semi-Perpendicular
Proponents of “Closed Chain” exercise would have us believe that it’s better (more safe) to use a Semi-Perpendicular lever (limb), than a fully Perpendicular lever, during any given exercise. They believe that a perpendicular lever magnifies the resistance too much. But, again, one selects the resistance they’ll use on the basis of how it feels. If we use a perpendicular lever (as in Leg Extension), we automatically select a lighter weight, because it feels heavier. If we use a semi-perpendicular lever (as in Squats), we automatically select a heavier resistance, because we’re able to.
If we were to compare the load placed on the Quadriceps / Patella tendon while using a Leg Extension machine, with a load produced by standard Squat, we could see that it
would be approximately the same. In other words, a 100 pound load on Leg Extensions (50 pounds per leg, with a 100% lever), is essentially the same as as 200 pound load on a Squat (100 pounds per leg, with a 50% lever). The Quadriceps and the Patella tendon don’t “know” – nor do they care – how the resistance they are getting is actualized. The Quads and tendons experience a load, but don’t know whether it’s produced with 100 pounds and 100% lever, or with 200 pounds and a 50% lever. Either way, the Quads / knees experience the same load.
Perpendicular Force Produces a “Shearing Effect”?
Proponents of Closed Chain exercise believe that perpendicular forces are dangerous because they produce a “shearing” effect on the joints. The most commonly cited example of this is the Leg Extension Machine. To be perfectly clear, the assertion is that a perpendicular force applied at the level of the ankle, would push back the upper portion of the lower leg (the Tibia), away from its normal position at the knee joint. This would strain or damage the ligaments of the knee – if it were correct. But it’s not.
Let’s re-visit their “Shear Force” illustration. As you can see, the depiction is of an upper leg (Femur) stacked on top of a lower leg (Tibia), and two arrows pointing in opposite directions. By the looks of the illustration (below), it would certainly seem that something would “tear” (break, snap, separate, etc.) – based on this graphic. However, this is not what happens during a Leg Extension exercise.
During a Leg Extension exercise, the Femur is stable. It is not moving, nor is it having any forward thrust imposed on it. The upper arrow, in the above depiction, is misleading in this regard – and that’s the least of what’s wrong with this illustration. Also, this depiction shows a “perpendicular force” applied in the middle of the Tibia (lower leg). That is NOT where the resistance is placed during a Leg Extension exercise. It is usually placed at the very bottom of the lower leg (at the ankle). This is very important, as you will soon see.
Lastly, this illustration suggests that ANY perpendicular force, applied anywhere on the lower leg, will cause the entire lower leg to shift in the opposite direction EVENLY. This is absolutely not consistent with the laws of physics. It DOES matter – quite a bit – where on the lever a force is placed, and also whether or not one end of the lever is held as a pivot. To demonstrate this, I’ve created two experiments.
Experiment # 1
In this first experiment, I’ve devised a make-shift Leg (Femur and Tibia). The two “bones” are held together by strings (photo below-right). These strings are meant to represent the ligaments of the knee. Keep in mind that these strings have substantially LESS tensile strength than do actual knee ligaments.
First, we’ll deliver a perpendicular force to the highest part of the “lower leg” – an area just below the “knee”.
As you can see, there IS a shearing effect produced in this particular example. The “shearing” is demonstrated by the direction of the strings, relative to the vertical angle of the lower leg… and also by the shifting of the “bone” (the top end of the lower leg) away from the end of the “upper leg” / “knee”. Now, in the second part of this experiment (shown below), we’ll deliver a perpendicular force to the lowest part of the “lower leg” – where the ankle would be.
As you can see, there is NO shearing effect produced in this example. The strings (“ligaments”) are still parallel with the lower leg – despite having essentially no tensile strength. Also, the top of the “lower leg” has NOT shifted away from the “knee”. The reason this is so, is because of a physics rule known as the “Principle of Least Action” (formulated in the 1700s by Pierre Louis Maupertuis, and used extensively ever since). In essence, if the Tibia could talk, it would say, “why would I need to shift up here (at the knee), when I can instead so easily sway down here (at the ankle) – thereby relieving ALL need to shift anywhere else?”.
In the first part of the experiment – when we applied the perpendicular force to the very top of the “lower leg” – it was difficult for the lower leg to act as a lever, since we were pushing so high on the “bone”. The only way the “bone” could absorb the force was by shifting back (shearing). However, in the second part of the experiment – when we applied the perpendicular force to the lowest part of the “lower leg” – it was very easy for the “bone” to sway as a lever. The pendulum-like sway of the lower leg, in this case, was the path of least resistance. It was the “release valve”. The perpendicular force was fully “absorbed” by this lever action.
Experiment # 2
In this second experiment, I’ve devised another make-shift Leg (Femur and Tibia). However, this time I’ve held the two “bones” together by way of a piece of rubber – representing the Patella tendon. Note that this piece of rubber is precisely in the place where the Patella tendon would normally be – on the front of the knee, attached high on the front of the “lower leg”.
Again, we will first deliver a perpendicular force to the highest part of the “lower leg”.
As you can see, there is some degree of shearing that is produced – although it is a bit less than in the first experiment. The reason it is less, is because the “tendon” is attached to the front of the knee, rather than alongside the knee – as the “ligaments” (strings) were. It’s placement, therefore, does a little better job of keeping the top of the Tibia from shifting back. Now, in the second part of this second experiment (shown below), we will again deliver a perpendicular force to the lowest part of the “lower leg” – where the ankle would be.
As you can see – again – there is NO shearing effect produced when the force is applied low on the “Tibia”. The rubber (“Patella tendon”) is perfectly in line with the “lower leg”. Also, the top of the “Tibia” has not shifted back, away from the end of the “Femur” (i.e., the knee area). The conclusion we can draw from just these two experiments, is that applying the perpendicular force to the “distal” end of the lower leg is PROTECTIVE of the knee. This is the complete opposite of the assertion made by supporters of “Closed Chain” exercise. Ironically, the lower one applies the perpendicular force, the more freely the lower leg is able to act as a lever, thereby relieving the upper end of the “Tibia” from needing to shift back (i.e., “shear”).
One More “Safety Feature”
We have already demonstrated that there is essentially no shifting (“shearing”) of the upper-end of the “Tibia”, when applying a perpendicular force to the “ankle”. However, there is yet one more feature that ensures no shearing effect on the knee, while doing knee extensions on the Leg Extension machine. It has to do with a secondary force provided by the Quadriceps / Patella tendon combined with applying the perpendicular resistance at the distal end of the lower leg.
When we do a knee extensions on a Leg Extension machine, we select a weight which we feel we can manage. As an example, let’s say we’ve selected 100 pounds (distributed between the two legs = 50 pounds per leg). That resistance is not the actual amount the Quadriceps must “move”, because the Quadriceps / Patella tendon is not pulling directly on the weight. Rather, the Quadriceps / Patella tendon is pulling on the lever that is pushing the weight. Since the attachment of the Quadriceps / Patella tendon is very high on that lever (the Tibia), the lever-length of the lower leg magnifies whatever resistance is used, by at least a factor of 20 (this also takes into account the angle from which the Patella tendon is pulling on the Tibia).
What this means is that the each Patella tendon is producing approximately 1,000 pounds of upward force (i.e., a “compressive force” – toward the end of the Femur / upper leg bone), while the perpendicular resistance at the ankle is still only 50 pounds. Thus, in addition to there being no shifting / shearing, due to the pendulum-like sway of the lower leg, there is also a force which is far greater than the perpendicular resistance at the ankle, that serves as an anchor to the top portion of the “Tibia”. This ensures a pivot effect at the knee, which further eliminates any possibility for shearing / knee displacement.
Again, the distal application (at the ankle) of the perpendicular resistance, provided by the Leg Extension machine, results in a PROTECTIVE effect on the knee. The lower on the Tibia one places the perpendicular force, the greater the difference between that force and the anchoring effect of the Patella tendon (adjusting resistance to accommodate the longer lever length).
Perpendicular forces are not dangerous; they are beneficial. Actually, they are essential to muscle loading. Without them, a muscle would have no resistance at all. Perpendicular forces do not pose an extraordinary risk to the joints involved, any more than do forces that are only semi-perpendicular, with equal net resistance. There is no shearing effect caused by Leg Extensions. In fact, if one wanted to intentionally cause a knee shearing, one would have to do much MORE than simply apply a perpendicular force to the upper portion of the Tibia. One would have to also apply an OUTWARD force on the lower portion of the Tibia (behind the ankle), while simultaneously applying an INWARD force to the upper portion of the Tibia, and ALSO eliminate the anchoring effect of the Patella tendon (i.e., relax the Quadriceps). Certainly, this would never happen during normal exercise.
Placing a resistance at the distal end of a limb (at the ankle, for example) is even more safe than placing it at half the length (mid-shin, for example)… which would necessitate a higher actual weight to be used, to compensate for the shorter lever length. Distal placement of resistance produces greater magnification, thereby diminishing the need to use a heavier actual weight. The idea that “Closed Chain” exercise is more “functional” is not necessarily correct. It depends on the goal. Also, muscles gain strength through any kind of resistance work. It does not matter whether a Quadriceps gains its strength while doing an exercise that combines the efforts of other muscles simultaneously, or not.
If all the muscles of the body were to gain their strength by way of isolated exercises, they would all work together just fine, when doing daily activities or playing sports. The only exception might be that of elite athletes who specialize in one activity, and are attempting to gain strength for that specific activity. An example of this might be someone training for Mixed Martial Arts (MMA). While it may be true that a compound exercise “theoretically” saves time, by working multiple muscles during a single exercise, it is NOT necessarily true that each of those participating muscles will benefit equally from that one “compound” exercise, as compared with each of those muscles doing other, better (more isolated) exercises.
It is also not reasonable to believe that all compound exercises are comprised of separate joint movements that are each, individually, safe. Sometimes they are, and sometimes they’re not. For example, Pull-Ups produce a degree of shoulder impingement; bodyweight Side-Planks could easily irritate a shoulder joint; Push-Ups can strain the wrists; Bench Dips over-stretch the anterior deltoids, etc. And there’s also the injury risk related to a person straining too much by using bodyweight. Yet Squats seem to be “easy enough” and mostly mechanically correct. So it depends on the exercise.
So, although a person may be “saving time” by doing compound exercises, he/she may be getting a compromised benefit and an increased risk of injury. Isolation exercises most certainly have benefit. Often times they have more benefit, and less risk to the associated joints, than do compound exercises – even if they do require a bit more time.
Certainly, they allow more freedom in terms of the selection of resistance. They’re also easier to do (allow for the proper resistance to be used), and therefore tend to be less discouraging than most of the bodyweight exercises.
Lastly, the argument of “Open Chain” versus “Closed Chain” is largely moot. For example, how would the Latissimus dorsi (muscles of the back) “know” whether the body is moving toward a Chin-Up bar, or a “Lat Pull-Down” bar is moving toward the torso? (…both use the same shoulder and arm movement)
Q: How would the Quadriceps “know” whether the body is moving away from the floor (when doing Squats), or the Leg Press sled is moving away from the body?
A: Both use the knee movement.
Q: How would the Calves “know” whether the body is moving away from the Calf Block on the floor, or the Leg Press sled is moving away from the heels of the feet?
A: Both use the same ankle movement.
Q: How would the Pectorals “know” whether the body is moving away from the floor (when doing Push-Ups), or the Bench Press barbell is moving away from the torso?
A: Both use the same shoulder and arm movement.
Ultimately, all muscles contract in their own, individual space. They pull their origins closer toward their insertions, thereby producing joint movement (flexion, extension, rotation, etc.). Whether that muscle contraction occurs with bodyweight or with free weight, and whether it occurs in unison with other muscles or not, those individual muscles do the only thing they can do – their primary task, whatever it may be.
“Skill training” and specific coordination movements notwithstanding, the arguments over which is better or worse (Closed Chain or Open Chain / Compound or Isolation), is mostly moot because a muscle that is challenged with resistance will gain strength and development, no matter what. What most determines the efficacy of an exercise – and therefore the benefit to each muscle – is how closely that particular movement follows the individual muscle’s primary function, and whether or not the resistance curve of a particular exercise is consistent with that muscle’s strength curve.
(Note: If a person has injured knees, it would be prudent for them to minimize the amount of resistance with which he/she loads his/her Quadriceps. The same would be true for any inured joint, in terms of the load placed on a muscle that crosses / engages that particular joint. But advising all people, even those with perfectly healthy, un-injured joints, to avoid perpendicular forces or isolation exercises, is misguided.)
This article has been endorsed by:
1. ISSA (International Sports Sciences Association / “pivotal article”)
2. Jeff Mackey, PhD (physicist who consults for NASA / “the engineering analysis is accurate”)
3. Chukwuma Ekwueme, PhD (structural engineer / “the physics is correct”).
About the Author
Doug Brignole is a veteran competitive bodybuilder, currently in his 38th year of competition, still competing at age 55. Having started at the age of 16, and winning numerous teenage competitions in addition to the Overall Mr. California, and his weight division in Mr. America and Mr. Universe, Doug now has his sights set the World Championship of 2014. He has been an enthusiastic student of biomechanics for many years, writes for a number of websites and magazines, and is now working on his second book. He has been certified by the American College of Sports Medicine and the American Council on Exercise.