[Author’s Note: This text was first written as introduction to an instructional video series, hence the reference in places to video and exercises. My initial intention was simply to share weighted ball exercises that will: 1) increase internal power (big time), 2) afford a very safe way to practice fajin, and 3) provide excellent cardiovascular exercise. But as I thought about how to teach the weighted ball exercises I quickly realized that the requisite for doing them is an understanding of the five (5) steps of storing and releasing internal power, and before THAT can be understood one must understand the physical mechanisms of internal power (nei jin (內勁) or, as I explained in Part I of this introduction, what I prefer to call the “learned power” of the Chinese martial arts). Below is Part II of the introduction to all of this, in which I explain the physical mechanisms of internal power—in other words, what internal power is. The reader may wish to first go back and read the first part of this introduction, in which I submit that the efficient, “learned power” of the Chinese martial arts is decidedly distinct from natural ability or “external” strength and that methods to develop efficient and learned physical power were refined by farmers and soldiers over the 2500+ year history of the Chinese martial art tradition. Development of this “internal” power is a fundamental, common goal of xingyi, yiquan, bagua, and taijiquan and is the subject of much of the classical writings of the Chinese literati, who quite belatedly embraced practice of martial arts in the late 19th century). ]
Introduction Part II: Mechanisms of Internal Power
There are four physical mechanisms of internal power (nei jin (內勁). We’ll get a little technical here, but understanding these mechanisms is essential to understand why the methods and principles of practice are what they are. The *PURPOSE* of each different component of fundamental training (sitting, standing, and lying meditation, qigong, forms, and push-hands) is to develop one or more of these four physical mechanisms of internal power. Let me say that again:
The *PURPOSE* of each different component of fundamental training (sitting, standing, and lying meditation, qigong, forms, and push-hands) is to develop one or more of these four physical mechanisms of internal power.
After understanding what internal power is we will then look at the five steps of storing and releasing internal power—the fundamental how of all internal martial art movement.
The four physical mechanisms of internal power from a Western biomechanical perspective, and their traditional counterparts, are:
- Neuromuscular Efficiency (= “Mind/Body Connection”)
- Core Strength (= “Dan Tian” Power)
- Stretch Shortening Cycle (SSC) (= “Elastic Force”); and
- Kinetic Chain + Ground Reaction Force (GRF) (= “Silk-Reeling + Ground Path/Force”)
Neuromuscular Efficiency is comprised of:
a. intra-muscular coordination—the recruitment, firing rate and synchronization of motor units; and
b. inter-muscular coordination—the coordination between different muscle groups, specifically interactions of agonist, antagonist, and stabilizer muscle groups.
In combination, neuromuscular efficiency allows maximum power (force per time unit), minimum energy expenditure, and improved accuracy of precise movements.
Of course muscles are recruited by bioelectric signals that are initiated in the brain and travel through nerves that act upon the muscles. This is the mind/body connection and is referenced by the traditional taiji saying that the yi (mind) leads the qi (energy) and the body follows, or the three “internal” Xingyi harmonies—heart harmonized with intention, intention with qi, and qi with power (body). Actually, these old traditional sayings remarkably parallel today’s scientific understanding of muscle recruitment.
Training neuromuscular efficiency is the purpose of the meditative, slow movement training of the internal martial arts, and recent scientific articles have reported that focused awareness on force targets outside of the body does improve motor unit recruitment patterns. [2-5]
 Lohse, Keith & Sherwood, David. (2010). The influence of attention on learning and performance: Two experiments in isometric force production. Journal of Sport & Exercise Psychology. 32. S106-S106. https://doi.org/10.1016/j.humov.2011.06.001.
 Lohse, Keith & Sherwood, David & Healy, Alice. (2011). Neuromuscular Effects of Shifting the Focus of Attention in a Simple Force Production Task. Journal of motor behavior. 43. 173-84. https://doi.org/10.1080/00222895.2011.555436.
 Kovacs, Attila & Miles, Garrett & Baweja, Harsimran. (2018). Thinking Outside the Block: External Focus of Attention Improves Reaction Times and Movement Preparation Times in Collegiate Track Sprinters. Sports. 6. 120. https://doi.org/10.3390%2Fsports6040120.
 Taylor, Molly & Golden, Grace. (2020). The Effect of Attentional Focus on Gluteus Medius Recruitment and Force Production. Athletic Training & Sports Health Care. 12. 272-282. https://doi.org/10.3928/19425864-20200922-01.
According to Wang Xiangzhai, founder of Yiquan:
The first step to take in learning boxing exercises is the training of one’s mind, and on this basis the ability to perceive the mechanism of the movements of all four limbs and bones . . . In the beginning, moving slowly and unhurriedly is better than moving quickly and hurriedly. The slighter the movement is, the more fully one’s spirit concentrates. ” 
 Essence of Boxing Science Interview with Mr. Wang Xiang Zhai – Part 2. Internal Arts International (accessed July 11, 2021). https://www.internalartsinternational.com/free/essence-of-boxing-science-interview-with-mr-wang-xiang-zhai-part-2/
Three of Grandmaster Feng’s 12 principles of practice refer to the importance of relaxed, mindful movement:
Grandmaster Feng Zhiqiang’s Twelve Principles of Taijiquan Practice
- Heart and spirit empty and tranquil from beginning to end.
- Central equilibrium.
- Use the mind to move qi. The heart is the commander.
- Start with sinking and dropping.
- Search for soft and smooth.
- Inside/outside and upper/lower should work together.
- The transition of yin/yang will help you find hard/soft.
- The silk-reeling force should be present throughout the body.
- Search for open/close by folding the chest and stomach.
- Concentrate on dantian to improve neigong (internal skill).
- Keep your heart calm, mind quiet, and practice slowly (stillness in movement). The form is a moving standing pole (huo zhuang).
- You will be successful if you know both how to practice and how to nurture yourself (yang sheng).
Of course the ultimate goal is to move very fast, with the additional accuracy and power afforded by improved neuromuscular efficiency derived from slow movement training. From here on as we talk about the mechanisms of internal power in our practices I’ll just simplify and refer to neuromuscular efficiency as RECRUITMENT. But what, you may ask, are the most efficient muscles to recruit?
The taiji classics say that “power is released from the spine.” It is the core musculature that flexes and stabilizes the spine. The stability of the spine and pelvis are critical for the maintenance of balance and posture. To quote Taijiquan, The Art of Nurturing, The Science of Power: “The core muscles are also critical for the transfer of energy from large to small body parts. Because the peripheral muscles of the shoulders, arms, and legs are anchored to the spine or pelvis, all power is either generated from or transferred through the core of the body. Greater strength of the core not only yields a greater power output, but also increases the neuromuscular efficiency of peripheral muscles—with a stronger core, less forceful contractions of the peripheral muscles are required to produce a given amount of power.”
Muscles can be classified as either stabilizers or mobilizers. Stabilizers hold things in place, while mobilizers move things around. This is a simplification, as some muscles can act as either depending on the movement, but in general stabilizers tend to be composed of more type I muscle fibers, while mobilizers are generally more type II fibers.
|type 1 (slow twitch)||type II (fast twitch)|
|oxygen burning (aerobic)||anaerobic|
|can stay engaged for a longer time||short burst of speed|
|deeper muscles (core)||superficial (ones we see)|
|smaller motor units (more finely controlled)||larger motor units (big, dumb)|
It is the recruitment of deeper musculature, especially of the lower core, that is significant in the generation of the “internal” power of the Chinese martial arts, and the principles and methods of practice are precisely intended to teach us to engage the core. When standing (or sitting!) in an upright posture and consciously relaxing, what you relax are the mobilizers—the things NOT needed to maintain the posture but are just wasting energy. Of course the stabilizers do not relax, or your body would just collapse.
“Move from the dantian” is an admonition known to all students of Chinese martial arts. Grandmaster Feng, with the tenth of his twelve principles, tells us to “concentrate on the dantian to improve internal gong,” His Xinyi teacher, Grandmaster Hu Yaozhen, said “Grasp and hold dantian to train internal gongfu.” While dantian means different things in traditional Chinese medical theory and Daoist meditation instruction, the Chinese martial artists mean the area of core musculature in the lower trunk.
While dantian means different things in traditional Chinese medical theory and Daoist meditation instruction, the Chinese martial artists mean the area of core musculature in the lower trunk.
Importantly, you will see that core musculature not only stabilizes, but also stores energy that generates movement—it serves as both a stabilizer and mobilizer. The focus on storing energy in the core and “releasing power through the spine” is perhaps the most unique force generating mechanism of the internal Chinese martial arts. Again, this power must be learned.
The stretch shortening cycle (SSC) is when the stretching of muscles, tendons and/or fascia precedes, and adds power to, a concentric muscle contraction. It is often likened to stretching and releasing a rubber band. Indeed, western scientists sometimes refer to the energy generated by the SSC as “elastic energy,” and it is precisely the SSC that is traditionally referred to as “elastic force” in the oral and written tradition of the internal Chinese martial arts. Again, it is quite remarkable how similar the traditional and scientific language actually is.
Another traditional term for elastic force is “sinew strength”—sinews of course being elastic collagenous tendons and ligaments that bind bones and muscles together. Wang Xiangzhai wrote:
“When the sinews are lengthened, your strength is great.”
 The Correct Path of Yiquan (1929). Wang Xiangzhai. (Paul Brennan, Trans.) Brennan Translation (accessed July 17, 2021). https://brennantranslation.wordpress.com/2016/08/31/the-correct-path-of-yiquan/.
Training the SSC is one reason why my teacher would often emphasize “elongation” in qigong and form movements. Qigong movements that emphasize dynamic stretching, for example the famous set of eight Yi Jin (Sinew Changing) exercises historically attributed to Shaolin training, or the very similar Eight Pieces of Brocade, are really emphasizing training of the SSC. [Of course any movement can include all four mechanisms of internal power, but some exercises emphasize individual mechanisms for focused training and quicker learning—beginners cannot possibly focus on all four from the start. We’ll learn which mechanisms of internal power are emphasized in different components of training as we get into the exercises.]
There are three phases of the stretch shortening cycle:
1. eccentric contraction—muscles, tendons and/or fascia elongate and store energy;
2. amortization phase—a “recoil” or release of the stored elastic energy; and
3. concentric contraction—producing a force that is the sum of concentric muscle contraction and the elastic energy.
The mechanisms of the SSC are not fully known, but it is understood that there are two ways in which force is produced in the amortization phase of the SSC:
a. neural: after sensing a stretch, muscles spindles send an electric signal (qi) through the spinal cord and back to the muscles fibers “telling” them to contract; and
b. mechanical: tendons and fascia directly release the mechanical energy stored in the stretch.
As a side note, the functions and types of fascia are only now beginning to be understood, but it is believed that the recoil of elastic fascia may be a significant factor in ballistic motion. One interesting characteristic is that fascia is a piezoelectric material—an electrical potential is generated when the fascia is stressed (i.e. stretched), and some have theorized that that is one component of “qi.” Another interesting fact is that fascia is also a sensory organ and plays a major role in proprioception (the body’s sense of posture and movement) and coordination.
The most common movement used to exemplify and explain the SSC is the difference between a static or “squat jump” and a countermovement jump. A squat jump is initiated from a static squat position, whereas a countermovement jump includes a quick lowering of the body followed by an immediate jump. As everyone knows, you can jump higher with a countermovement jump, and the reason is the greater force afforded by the SSC as elastic energy is stored and released in the leg muscles and tendons.
But the SSC is an important mechanism of power in myriad sports actions: the stretch as a batter steps toward the ball and rotates backward at the waist before swinging, the wind up of a pitcher, the elongation in a tennis player’s body as they prepare to swing, the wind-up of a boxer before swinging, the elongation of a quarterback’s body as he extends his free hand and pulls the ball back before throwing it, the storing of coiled energy in a golfer’s swing—the SSC is the energy of any stretching or elastic wind-up motion.
When teaching form or moving qigong my teacher would often say “if you want to go right, you have to go left first”—THAT is the SSC. As we will learn, the SSC or “elastic force” is trained and engaged in several ways in the generation of internal power in Chinese martial arts.
The first three of the four mechanisms of internal power all emphasize storing energy. Another thing my teacher would often say is “How much you can store IS how much you can release.”
“How much you can store IS how much you can release.”
– Dr. Yang Yang
This is basic Newtonian physics—kinetic energy cannot be greater than potential energy. Along with the essential principle of nurturing, it is also why the emphasis in practice is on storing, not releasing, energy.
The fourth and final mechanism both adds to power generation and is the means of efficiently expressing that power once released, and is:
The function of kinetic linking is to transfer and multiply energy as it travels through the body to the extremities of the hands or feet.
The academic definition of kinetic linking will sound familiar to students of the Chinese martial arts:
“The kinetic link principle is applied when different body segments rotate during throwing and kicking. These actions have been likened to the motion of a bullwhip. If segmental rotations are free to occur at the distal end, the body’s base-segments in contact with the ground act like the handle of a bull-whip. Just as the tip of the bullwhip can be made to travel at supersonic speed, the small distal segments of the hand and foot can be made to travel very fast by the sequential acceleration and deceleration of the body segments.” 
 Overview-The Kinetic Principle. Oxford Reference (accessed July 10, 2021). https://www.oxfordreference.com/view/10.1093/oi/authority.20110803100037256.
This is precisely one of the two functions of silk-reeling. Silk-reeling is the kinetic chain. Silk-reeling is a taiji term, but all internal arts train it. Silk-reeling is not something you “do,” rather it is the spiraling movement naturally generated through coordinated 1) weight shifting, 2) waist turning, and 3) chest/abdomen opening/closing with an upright and relaxed body. In short, it is the natural result of any movement performed in accordance with the postural and movement principles of the Chinese martial arts. In addition to transferring and multiplying energy as it travels through the body, silk-reeling also has a defensive function—the spiraling movements allow for efficient neutralization of external forces acting on the body. This defensive application is practiced in push-hands, but for now we will focus on the function of silk reeling in the generation and expression of internal strength.
I’ve grouped the Kinetic Chain (Silk-Reeling) and Ground Reaction Force (GRF) as they work together. Well, all mechanisms of internal strength work together, but the GRF is part of the kinetic chain in punching or striking. To understand this we have to understand the basic mechanics of a strike.
An influential paper published in Russia in 1985 (cited over 50 times in the academic literature) first reported that elite level boxers, and more powerful punchers, used the rear leg more to initiate the punch, and had better coordination of leg, waist, and arm movements, than lesser skilled boxers. 
 Filimonov, V., Koptsev, K.N., Husyanov, Z.M., & Nazarov, S.S. (1985). Boxing: Means of increasing strength of the punch. National Strength & Conditioning Association Journal, 7, 65. https://journals.lww.com/nsca-scj/citation/1985/12000/boxing__means_of_increasing_strength_of_the_punch.16.aspx.
Regarding the importance of the rear leg, the Xingyi Manual of Liu Dianchen says the same thing:
“Success depends entirely on the pressing down of the rear foot . . .The feet are seventy percent of the attack.” 
The coordination of the leg, waist and arm movements is the kinetic chain, and the rear leg force is Ground Reaction Force (GRF) that initiates the punch. The first phase of a powerful straight boxing punch then is a push off from the rear leg, which generates an initial vertical force up the leg. [A second vertical GRF is also generated by the necessary bracing action of the forward leg.] The vertical forces are transferred to a horizontal force through coordinated waist, arm and shoulder rotation.
These mechanics are now well known in the “sweet science” of western boxing. Google “kinetic chain” and “boxing” and you will get over 400,000 hits. Here is a excerpt from the National Geographic Fight Science video series that illustrates the kinetic chain in a boxing cross punch pretty succinctly, if not a bit over-dramatically:
Again, note the similarity of the narration in this modern analysis of a boxing punch with the traditional language of the Chinese martial arts:
“a perfect flow of energy through the entire body . . . like the coiling and cracking of a whip, the energy multiplies . . . as it flows through the body, travels out the arm and fist, and snaps into the opponent.”
We’ll explain the mechanics of issuing striking force in detail in our training, but I would like to say a few words here about the traditional terms “ground force” and “ground path.” Unless there is an earthquake conveniently happening at the time of your force expression or fajin, there is NO force generated by the ground. Remember—all force transmission requires transfer of kinetic energy, which is the energy of movement. There is no “empty” or magical force in the martial arts currently unknown to physicists, and the only measure of any striking force is equal to mass x acceleration. As I said in Part I of the this introduction, if you can prove otherwise to the scientific community a Nobel Prize and fame and fortune surely await you.
Three points I briefly mention here are that:
1. ALL force is generated by YOU
The GRF is simply Newton’s third law: for every action there is an equal and opposite reaction. When you push against the ground the ground pushes back with an equal and opposite force. The magnitude of that force is determined by how much force you can generate—remember, how much you can store is how much you can release. True, there is “borrowing force” from an opponent or from gravity, and we will cover that in our training, but even though some energy may be borrowed any external force must be transferred to and released by your musculoskeletal system, and there is no force generated by the ground.
2. In Chinese martial arts, there is more to generating GRF than “pushing with the legs” as described in academic papers examining boxing punches.
We’ll cover this in detail as we learn the five steps of storing and releasing internal power. This I believe, is really the unique part of the Chinese martial arts.
3. The “ground path” is the GRF in reverse—it is a mechanism of external force absorption/neutralization and is a combination of the fundamental mechanisms of internal strength and postural principles for training them.
Ground path is taught in basic push-hands. Though we won’t get into push-hands in this video series, the ground path will be made clear in the first of the five steps of storing and releasing internal power.
To conclude and further demonstrate the similarity of modern science and traditional explanations of the kinetic chain and GRF, here is an image from an academic paper illustrating force transmission in a boxing punch :
Again, a nearly vertical GRF force is transmitted upwards through the legs (the force is illustrated here only in the rear leg, but there is also a second GRF generated from the front bracing leg), spirals around the torso and shoulder, and is expressed horizontally out through the arm. This illustration immediately brings to mind Chen Xin’s famous early 20th century illustration of Silk-Reeling energy:
Chen Xin’s writings are very esoteric, but he does speak of silk reeling as connecting energy from the “toe” to the “finger”—i.e. from the “root” in the foot through the body.
There is nothing new under the son, and today’s scientific understanding of the kinetic chain of an efficient strike was well understood by the Chinese martial artists of old. There is, however, more to the mechanics of the power of Chinese martial arts than what is understood or has ever been addressed by academics, and that will be our next topic.
Summary and Next Step
Understanding what learned power is—neuromuscular efficiency, core strength, the pre-movement counter stretch yielding elastic energy, and kinetic chain/ground reaction force— is the why of practice. Every component of practice develops one or more of these physical mechanisms of power generation and expression.
The next focus will be on the how of practice—explaining the five steps of storing and releasing internal power. These five steps are well documented in the written and oral tradition and are contained within every movement of every form of every style of taiji, bagua, or xingyi. That, too, is worth repeating:
These five steps (of storing and releasing power) are well documented in the written and oral tradition and are contained within every movement of every form of every style of taiji, bagua, or xingyi.
The five steps of storing and releasing internal power are how energy and power are developed and used and are precisely what distinguishes “full” from “empty” practice. Indeed, I tell the students in our group that to understand the form they must be able to identify the five steps of storing and releasing power in each movement.
Nobody has ever told me any of this, and all is purely my own insight from a background in combat sports and 35 years of continuous, sincere and dedicated practice. I welcome any corrections, discussion or questions.
The Five Steps of Storing and Releasing Internal Power
Those familiar with Grandmaster Feng’s teaching will recognize the first of the five steps of storing and releasing internal power: “start with sinking and dropping.” This of course is the fourth of Grandmaster Feng’s 12 principles of practice, and the “start with” part clearly indicates that it is one of the first things to be learned. But what does sinking and dropping mean, and why and how is it done? To be continued . . .