No, Ki Energy Does Not Explain the Unbendable Arm (Not even when the assertion is published in an academic journal)

A few years ago, I saw a link to an article titled, "The Physiological Study of Ki in Ki Aikido (2)" (PSoKiKA2) published in the Journal of International Society of Life Information Science in 2001. As a person who used to practice aikido (a lot) and who still dabbles in it from time to time, the concept of Ki and the practice of Ki Aikido were familiar to me.

And I've long felt they they were bunk.

What is ki?
Okay, so I've revealed my position right away, but the evidence for the physical existence of ki is paltry at best; along the lines of evidence for ghosts, bigfoot, and the yeti. Indeed, the idea of ki is an embedded concept in Japanese culture, and it is used in forming many words (denki: electricity, kibun: mood, tenki: weather, and aikido: literally "harmonious-spirit way"), and it also has a spiritual/religious meaning. A good analogue of ki is the word (and concept of) pneuma, which has the double meaning of "breath" and "spirit/soul": it has both a physical and a mystical meaning. Indeed, like pneuma, ki is often associated in its physical manifestation as breath, especially in the spiritualistic extremes of Aikido practice. It also has a history of deep associations with Far-Eastern religions (much like pneuma had a history of deep mystical and religious associations in Classical Greek society and - through the works of Aristotle and the Stoics - the pre-Enlightenment concept of medicine, too).

Assessment of PSoKiKA2
Anyway, back to "The Physiological Study of Ki in Ki Aikido (2)." The article is built on the whole notion that the ki in Ki Aikido is a quantifiable physical phenomenon, with the very first sentence in the introduction unequivocally stating:

Aikido is a Japanese martial art, in which Ki is very important and is not always a physical power. (1,2)

Yes. There are references.  In fact, the article cites a total of three references, each one of them about Ki Aikido. In this case, references 1 and 2 are books in the popular press about Ki Aikido (Ki Energy for Everybody and Ki in Daily Life). The final reference is actually the complement to this study (or "PSoKiKA1"), which was published in the March issue of the same journal.

The methodology seems to be okay, but remember that the whole article is resting on the (untested) axiomatic premise that ki is real and can be measured. The introduction continues, though, thusly:

To identify what Ki is in Aikido, we studied what physiological state is controlled when the unbendable arm is performed. The experiments to study the state of the unbendable arm consist of three different conditions: (1) the state of the arm being unbendable by applying only physical power, (2) the state of the arm being unbendable by being powerless without resistance, and (3) the state of the arm being unbendable by extending Ki. Through analysis of the differences among the three states examined, the difference between physical power and Ki should be understood.

Um... Yeah. A little explanation is needed here, I think. First, what is "the unbendable arm"? Here is a quick video explanation (with a bunch of mumbo-jumbo, but not that much of it) that also shows the three conditions of the experiment (the guy in the video calls state (2) "floppy arms"):



In short, when you do the unbendable arm, your arm cannot be (easily) bent by your partner, even if they are trying really hard to bend your arm (which is why it's called "unbendable arm"), and it's a concept that exists in other martial arts, too. All the stuff about the poses is hooey, and you definitely can do it as a party trick to impress people. (But it rarely does impress people, unless you use it to show a person doing pull-ups on your arm.)

Going back to the PSoKiKA2, the researchers hooked up a Ki Aikido master a bunch of apparatuses to see what physiological effects and brain activity there are when the master is (1) actively using muscular strength to resist someone trying to bend his arm, (2) using nothing to resist the person bending his arm, and (3) using the unbendable arm technique to resist someone trying to best his arm.

Not really a bad set-up, except for the premise that what makes the unbendable arm function is ki. *sigh*

Still, PSoKiKA2 gets what looks like decent data and shows that the physiology and brain wave activity is different between condition (1) and condition (3). (Side note: condition (2) is treated as if it were a refractory period between the two tested conditions, and ought to be no different than the baseline condition that was measured prior to condition (1)). Specifically, the results showed:

• Relative to condition (2), the heart rate was elevated under condition (1) but not condition (3).
• There was more blood flow at the neck under condition (1) than condition (2).
• Both condition (1) and condition (3) showed almost instant blood pressure increase, but it was higher for condition (3).
• GSR increased sharply under condition (1) but not condition (3).
• Abdominal respiration ceased under condition (1) but was continued under condition (3).
• Neck temperature decreased under condition (1) but increased under condition (3).
• Condition (1) showed both alpha and beta wave brain activity, but condition (3) showed only alpha wave brain activity and no beta wave brain activity compared to condition (2).

Now, I would look at these results, and I would say that this conclusively shows that this Ki Aikido master is doing something very different between condition (1) and condition (3). In fact, that's all that PSoKiKA2 can show. If I had data from other subjects (like other aikido masters or complete off-the-street novices who were taught the basics of the unbendable arm mere seconds before testing), then I would be more comfortable to say that condition (1) and condition (3) are not merely artifacts created by the practitioner. (As an aikido practitioner, though, I would say that they aren't, but the data of one individual do not support my personal experiential - and therefore potentially subjective - observation.)

However, this isn't what PSoKiKA2 concludes. Indeed, here's what the authors thought the results meant:

... when resisting with Ki, the subject kept breathing and the exhalation dominated when starting to resist the power, this is presumably the factor functioning to resist the power applied.

... Coordinative function of the frontal lobe of the left-brain with the region for vision in the right brain was observed. The force through Ki might generate this connection.

Yeah, mumbo-jumbo that is also self-confirmatory. Ki and breath are always connected, as is ki and the mind. Finding these things is not proof of ki, but is either an explanation of acculturation or associative physiological processes. For example, in Aikido, we are taught a form of demonstrating the unbendable arm in which we don't breathe when physically resisting. See what the instructor does from 1:00? He purses his lips when not talking; when watching a similar demonstration in other dojos, this is often done unspeaking and with a clenched position. To one extent, it's play-acting. To another extent, it is true that if we are actively resisting, it's difficult to breathe easily, but for the purposes of demonstrating the unbendable arm, it's not so difficult as to cause you to cease all breathing. (Here, the Aikido master in the study either consciously or unconsciously play-acting the role assumed in the active resistance portion of the demonstration.)

So what do I think causes the unbendable arm, if it isn't ki? Well, I think that it's two things: mechanical advantage in work and physiology.

Mechanical advantage in work (aka the dot product of orthogonal vectors)
Waaay back in undergraduate (or maybe high school), when we took physics, one of the things that we learned as a part of kinematics was the concept of the dot product. Now, dot products are important in kinematics, since forces can be represented as vectors, and vectors can be manipulated using that specialized area of algebra called linear algebra.

One of the more important lessons that we learned in basic physics (the one that tries to teach kinematics without relying on the students' knowledge of linear algebra) is that the dot product of orthogonal vectors is always equal to zero. In other words, the net work done by perpendicular forces is nothing. Nada. Zilch. Zeeero. (And - conversely - the net work done by parallel forces is always equal to one or negative one, depending on directions of the vectors.)

Why is this important?

Well, the unbendable arm is actually - on one level - about the application of forces. The one trying to bend the arm (the "partner") is actively exerting force on the arm of the one resisting the arm-bending forces (the "practitioner"). In order to not have his arm bent, the practitioner must be exerting a force, because of the Law of the Conservation of Energy.

When the practitioner is actively resisting by pressing back on the partner's force, they are effectively creating a force vector that is parallel to the partner's force vector. In practical terms, this means that the maximum potential force can be imparted in the task, and the person exerting more force will be able to bend the arm in the direction they want. Since the partner has better leverage (and is usually using two arms), the partner is almost always able to overcome practitioner's ability to exert the force necessary to keep his arm extended.

However, when in the unbendable arm, the practitioner actually exerts force perpendicular to the forces exerted by his partner. Watch the video again, especially from 1:30. The force that the instructor is exerting is actually in the direction in which his fingertips are pointing: roughly perpendicular to his partner's hand positions. Since the angle between the forces approaches 90 degrees, the total amount of force that can be exerted by the partner on the practitioner approaches zero, which makes it very easy for the practitioner to utilize muscle force to counteract the remaining force exerted by the partner.

This isn't only the case when you have a partner using their hands and arms to try and bend the practitioner's arm. It also works with simple weights strapped across the arm at the inside elbow (provided the practitioner can stabilize his wrist and hand on something). So long as the practitioner extends a forward force, the weights will not bend his arm. It still takes work, though, since the force vectors are not at precisely 90 degrees, nor is there any feedback that the practitioner can receive from the weights, which is why it's actually harder (at least in my experience) to do unbendable arm with dead weights. But this leads to the next factor: physiology.

Physiology (specifically the stretch reflex response)
The actions of the human body are not purely the realm of abstract kinematics. The forces it creates are derived from the musculature. No surprise there. However, human skeletal muscle has a stretch reflex response, and:

When a muscle lengthens, the muscle spindle is stretched and its nerve activity increases. This increases alpha motor neuron activity, causing the muscle fibers to contract and thus resist the stretching. A secondary set of neurons also causes the opposing muscle to relax. The reflex functions to maintain the muscle at a constant length.

Gamma motoneurons regulate how sensitive the stretch reflex is by tightening or relaxing the fibers within the spindle. There are several theories as to what may trigger gamma motoneurons to increase the reflex's sensitivity. For example, gamma co-activation might keep the spindles taut when a muscle is contracted, preserving their stretch-sensitivity even as the muscle fibers become shorter. Otherwise the spindles would become slack and the reflex would cease to function.

In short, skeletal muscle has a way of maintaining a certain level of stretch in them that helps maintain the lengthened arm position by creating fine-level manipulations within the muscle fibers to ensure that the overall tension of the musculature is maintained unconsciously. This is important when describing the difference between doing the unbendable arm with a partner and with weights.

When practicing with a partner, the stretch reflex response continuously recruits different muscle fibers to optimize maintaining the position of the arm in its outstretched position. As the partner shifts his leverage (even minutely), muscle fibers in the practitioner's arm are automatically recruited and relaxed, which means that the practitioner isn't consistently using the same muscle fibers to continue keeping the arm extended.

Conversely, when practicing with weights, there is no shifting. (At least, there shouldn't be.) The weights have a constant, unchanging downward force due to gravity, and (if the stabilization point is a fixed surface) the stabilization point is also exerting a constant, unchanging upward force on the back of the hand. The stretch reflex response is to continue to keep the exact same muscle fibers recruited and leave others unrecruited. This means that the arm quickly tires (unless the practitioner moves his position or unless the practitioner uses the partner's shoulder as a stabilization point, or both).

Indeed, we would encounter this type of problem were we to simply keep an arm raised at shoulder height. We might start off by keeping the arm perfectly still, but our shoulder would quickly start to fatigue, and we would be sorely tempted to either drop the arm or move it to a different position. Even rotating the arm or changing the angle of the shoulder or bending the arm at the elbow will suddenly make the task feel easier (at least for a time). This is because the stretch reflex response recruits different unfatigued muscle fibers and releases fatigued ones in order to maintain the new position.

Closing Remarks
I don't know for certain that the unbendable arm is actually caused by the realization of the dot product of forces combined with the stretch reflex response in the arm, but these two things actually have an internal logic and consistency to them that ki doesn't have. If we believe that it was actually ki energy that kept the arm straight, that would mean that the practitioner can convert the partner's physical energy into ki energy. It also means that the process of such energy conversion just happens to look like it takes advantage of the dot product of orthogonal vectors on the physics side and the stretch reflex response on the physiological side.

In short, one doesn't need to rely on mumbo-jumbo non-explanations like, "it must be associated with ki," unless you happen to be using the concept of ki purely in its ineffable sense. However, to write a physiology paper that effectively says that we can measure and observe ki in the body's response to a set-piece in Aikido circles is akin to citing the "power of intercessionary prayer" in healing the cataracts in Sam's mum:



... and the evidence about the studies of the efficacy of the power of intercessionary prayer is that the studies are heavily biased with internal assumptions that cannot be tested, are - at best - serendipitously aligned with the outcomes that the experimenters expect to see, and so riddled with confirmation bias that negative or null outcomes are often explained away or not even included as "valid" results.

Take home messages:

1. The PSoKiKA2 study does nothing to actually show the existence of ki.
2. The unbendable arm can be explained through simple kinematics and physiology.
3. Heavily biasing your scientific research with predetermined causative effects means that you will certainly draw the wrong conclusions from your science (even if your method of obtaining the data was decent or even good).