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Episode 13: Force without Force

Pushing an opponent without force seems to defy reason and common sense. But it is a hallmark of tai chi, and is a concept known to advanced martial artists of all styles. The good news is that you can make sense of it without denying Newtonian mechanics or crossing over to the dark side.


One of the things, I think, that my students and my teachers find annoying about me, is my tendency to think. More specifically, it is my tendency to talk about what I think, especially since I usually go through a phase where I think that what I think is correct. That doesn’t last forever, however, which is good.  But, unfortunately, when I start to think that what I think is not correct, I just go on to start thinking something else, which I then spend time talking about and thinking

that the new thing that I think is correct.

So, anyway. Here is what I think.

Tai chi students like myself talk about pushing an opponent without using force, and the idea that tai chi can allow them to defeat a much bigger and stronger opponent without using force. We are taught this. We have methods for developing this skill. We can even demonstrate how it works. Some of us then go on to get smacked down by martial artists who clearly don’t understand that the tai chi master was supposed to be able kick their butt.

Part of the problem is that tai chi teaches profound, advanced martial art concepts to people who are not very advanced. It’s like teaching quantum physics to preschoolers who then start to think that they can bring a dead cat back to life by putting in a closed box and lying about it being dead. #Schrodingerscatsequeltheressurection #Schrödinger #cat #sequel #resurection.

Concepts and principles that were historically taught to experienced martial artists are now taught to beginners who have no context for them. 

I teach tai chi, and other martial arts to beginners. But many of my students come to me after years of training in other martial arts. At times, half of my students are black belts, or equivalent, from other styles. I must say it is sometimes quite intimidating to teach tai chi combat principles to people who could easily rip my arms off and beat me to death with them. Fortunately, expert martial artists are some of the nicest people you will ever meet.

But the popularity of tai chi as a healing. exercise means that many classes don’t teach any martial art basics. Students might learn forms and tuishou, and two-person routines. But they never do any real combat training.

They don’t practise applying the principles in real situations.

My friend, Adam Chan, once said that for most people, “Learning tai chi is like trying to build a supercar in your basement.”

He is right. You might be successful at building the car if you have a good understanding of the engineering and physics involved. But the car will be useless until you can figure out a way to get it out of your basement. Even then, you still haven’t learned how to drive, and learning to drive is not just about theory and having a good car. You also need experience. You need the time to develop skills, reaction time, and a set of strategies that account for other drivers, changing weather, and the rules of the road.

Other martial arts get the student on the sidewalk right away. Then they get them roller skates. Then they get them bicycles and teach them the rules of the road. Then they spend years upgrading the bike to progressively better motorcycles, or cars. By the time that the rare student upgrades all the way to a supercar, they have already been driving for years.

Most tai chi students, and some teachers have not gone past the rollerskate stage of combat. But most people who start learning martial arts do not get much past the rollerskate stage. There are many tai chi students who have spent years engineering their vehicle in the basement. But their design is based on static vectors and simple curves, and they have not tested the materials for kinetic stress.

On the other hand, Tai chi can be like turning you into a boat, instead of just teaching you how to swim. It can transform your body and mind in ways that weaponize your natural instinct. You don’t have to think about swimming techniques or fatigue. The boat will take care of you, and you will be better off than a swimmer when the weather turns.

A friend of mine, was in her 70’s when thieves tried to steal her purse. One of the thieves distracted her by grabbing one of her arms and yelling loudly in an unknown language, while the other thief attempted to slip thepurse off her other arm. The pull on her left arm caused her to pivot naturally to her left, bringing her right foot forward. This caused the first thief to fall onto his back. Then the tug on her purse caused her to stumble backward. Her right foot took a big step backward. Then her right arm shot up into the air as she pivoted around her right hip. As she regained her balance, her purse strap slid back onto her shoulder and the second thief was sprawled on the ground. As the two men fled, she was still trying to figure out what happend. Later, she commented with some glee, “Oh! That was White Crane Spreads its Wings!” She was not an expert fighter. But her natural instinct, born partially from her tai chi practice, showed how tai chi can reduce falls in seniors, and cause falls in purse snatchers.

Tai chi develops a quality that is essential to martial artists, and extremely useful in everyday life. It affects balance, power, natural instinct, and a dozen other qualities that are more fundamental than martial technique. But most martial arts only teach them to advanced students, or let them discover it for themselves.

Peng is a term that is unique to tai chi. It is at the basis of tai chi as a martial art. Everything about tai chi, whether for martial arts or health, is dependent on understanding peng. Peng is the basis of all tai chi posture and movement. If tai chi were a symphony, it would be in the key of Peng.

By the end of this video, I hope you have an idea about what peng is. But first, I want to tell you what peng does.

It can do a lot of things.

Peng allows you to move an opponent, to withstand or counter their force, without using force. It lets you push without pushing. It allows you to bounce the opponents force right back at them, without using force. It allows you to be unaffected by the opponent’s force. It lets you do all of these things and more, in spite of these things all being impossible.

Peng, like many subtle skills in martial arts, defies reason and common sense. I like things that defy reason and common sense, because I like science. 

One thing I learned from crashing university physics lectures to impress a girl when I was a teenager, is that common sense is very bad science, and things that seem reasonable are false at least as often as they are correct. For example, in the 19th century, the greatest doctors in Europe considered it reasonable that diseases could be caused by bad air from smelly places like swamps, slaughterhouses, or sewers. There was lots of evidence for it. People got sick near swamps and sewers, and abattoir’s, even if they didn’t go inside them, or touch them. But the experts did not think it reasonable that thousands of people could be killed by a microscopic germ. Those scientists are all dead now.

In a fight, your opponent is literally trying to stress you out. They apply forces in various directions, with confusing combinations of momentum and kinetic energy, in order to move you or change your shape in ways that make you unable or unwilling to continue fighting. They might punch, push, twist, trip, throw, yell, grimace, or call you names. The more these things affect you, the more difficult it can be to adapt to those changes. So, it would seem that you either have to become harder to affect, or better at reorganizing around the changes. But there may be a third option, or a fourth, or…OH! a fifth!. Wow. That would be cool.

Today, I will discuss peng in terms of pushing, because that is the language that tai chi uses for teaching this basic concept. But it should be remembered that peng can be, and must be, applied to striking, twisting, throws, and every other kind of attack and defence.

Remembering Newton’s Third Law of Motion, when the opponent pushes you, the push happens to both of you. (For every action there is an equal and opposite reaction.) There is no simple mechanical difference between attack and defence.

The deformation and displacement will likely happen more to one of you than to the other.

This difference is the result of your relative mass, your ability to direct force through or away from you, and the collective elastic modulus of each person. So, the effect of a push depends on how heavy you are, how skilled you are, how you are standing, and how hard you are.

Elastic modulus:

Elastic modulus is the measure of how hard it is to change the shape of something. Diamond has a very high elastic modulus, which means that it takes a lot of force to stretch it. Elastic bands, however, have a low elastic modulus, and are easy to stretch.

Kinds of elastic modulus:

Tensile modulus measures stretchability and compressibility along an axis. Tensile stress is caused by the normal force of the push at right angle to the surface.

Shear modulus measures shear-ability (Not sheer ability) – the force required to rend or twist something. Shear stress is a force parallel to the surface of the material.

Bulk modulus measure the stretchability and compressibility in all directions, the force required to inflate or deflate, to change the volume of a material.

In real life, all of these stresses are involved in the push. The push might start as tensile stress along one vector, but as the pressure increases or the body is compressed, then bulk gets pushed outward from the inside, and changes in shape cause the push to diffuse and change direction. The push that started pushing you one way, causes forces to go in all directions. When I shovel snow, the snow does not always go the way I push it. Some of it goes sideways, or upward. If you stretch something, you have to grab

it and pull, that means you are applying a shear stress and tensile stress against one surface in order to apply the tensile stress to another.

In high school science class, stress was usually talked about in static terms, which made it easier to talk about, and made the math simpler.

In reality, stress changes its target as the strain increases. If you push on a chunk of coal long enough, it becomes a diamond, or it becomes many different chunks of coal, or it starts to burn, or it get pushed away. It all depends on the nature and circumstances of the interaction. In martial arts, peng is how you manipulate the nature and circumstances of the interaction.

One of the things that peng does, is align the body in a way that redirects the push into the ground. What starts as a straight push gets redirected by an adaptive geodesic. You receive the opponent’s push and guide it along a path that curves around and through you on it’s way to the centre of the Earth. When it is applied well, peng makes their push as futile as pushing the Earth itself.

When you perform peng tactically, the other person finds themself uprooted by their own push.

If this is difficult to understand, think of archways in the Roman aqueduct at Pont du Gard, which has stood for 2000 years. Archways redirect the force into the ground in a way that preserves the structure. This is different from normal post and beam construction where the weigh of the structure puts stresson the middle of the beam and causes it to bend over time. Peng uses the centripetal geodesics the same way. The curve is more complex than an archway. It is more like a spring, coiling around the muscles and through the fascia.

Each coil of the spring will break if it is poorly aligned or is subjected forces strong enough to negate Hooke’s Law.

If you are not connected to the ground, it doesn’t matter how good or solid your connection is. The push will displace you without much effort. But if the push is connected to the ground, then the push will be redirected into the earth, and you won’t be able to push it as easily.

There are two things that people call peng, and I often refer to them myself.

Peng can be hard or a soft. Hard peng deals with greater force, and soft peng deals with faster changes.

Hard peng can deal with a lot of force. But is really only practical for a very short period of time. whereas, soft peng makes faster changes so it doesn’t have to deal with a lot of force. Hard peng is what we use when soft peng fails. It depends on increasing the bulk modulus to support the tensile modulus.

What does that mean? Okay….here….

Look at this stretchy blob. It is called “stretchi Blob.” I bought it at Lahays craft store downstairs here in Orillia. You will notice that, when I push on it from the top, I am applying a normal tensile force. When I first start to push, it gets shorter. But as I add more pressure, it begins to expand in all available directions.

It is fairly elastic. So, it reverts to to its original shape when I stop pushing.

If I put it in its box, the box holds the sides in, and the reaction force, or restoration force makes it harder for me to push. However, if I push hard enough for a long enough time, the box fails and the blob forces the side door open.

Now, this is how hard peng works. We selectively firm up the body in order to increase the body’s collective bulk modulus, making it harder for the opponent to squash us in any direction…especially in the direction of the push. So, somebody pushes on my forearm. But the forearm doesn’t collapse because I’m using this balanced tension in my body and my arm to hold that shape, and this a very easy shape to hold, relative to this shape or that shape. So, this alignment is really good.

And I align the chest and back properly so that I can firm up the body, and make it very solid in all directions so that it can’t be squashed and the forces don’t go out to the sides. And, I align the spine so that the power goes down into the ground. I use my core muscles to connect the top to the bottom, right through the centre here.

That way, when the push comes in, it gets redirected. All of the vectors of force that I create add up to that one really good centripetal geodesic. So, any forces that push the line that way or that way, balance each other out.

So, if I apply a force this way, then I apply a force that way. So, I manage to create a balance among all of these outward going vectors, to conspire with this spiralling geodesic and connect it to the ground. It sounds great, and it can work really very well.

That is how hard peng works. We selectively firm up the body parts to increase the body’s collective bulk modulus, making it harder to squash in any direction, especially the direction of the push.  In a fight, hard peng, combined with a tactical change, can cause the opponent’s peng to fail.


The hard approach to peng is relatively static. It depends on the physical manipulation of the tensile modulus and bulk modulus of the body. 

This means that you strengthen the body from the core to the extremities in a way that can make you capable of withstanding greater forces. It is important that the tension serves the tensile modulus, meaning that the firming of the body does not cause one to lose focus on the direction of the opponent’s push, and does not give the attacker the ability to push you in more than one direction. You do not just close your eyes and tense in all directions. You must remain aware of the push and the connection to the ground. If you only remain tense, they can push you in any direction and still move your centre. 

Effective hard peng can withstand a great deal of force. But it is only practical for very brief moments. The tension must not last longer than the opponent’s reaction time. This is why training hard peng requires you to work with training partners who are able to react, not just lean on you and then let the restoration force bounce them away.

I don’t just push on my opponent like this.

I have to be able to change the direction of the push so that they can practise adapting faster than I do.

Soft peng, by contrast, is continuous. It can remain practical over time, even as the opponent adapts. But it is only practical for a limited range of force.

It can be continuous and flow and be very effective. But when the pressure builds up, the soft peng doesn’t work so well.

As the push begins, soft peng engages the centripetal geodesic, directing the push along curves through and around the body until it connects with the centre of the earth.

But as the push continues, if the pressure increases, it starts to interact with the bulk. This is when soft peng must adapt or die. It does this in a number of ways.

1. Changing the surface area: The normal force of a push is directed perpendicular to the surface area, and is measured in force per square cm. By reducing, to a single point, the surface area that receives the force, and by making the geodesic infinitely thin, you can reduce or eliminate the bulk effect throughout the body. If you focus peng on a single point, the surface area is zero.

Any reaction force – pressure per square cm – will be undefined, because their are no square cm. If you try to maintain a single point, the opponent will adapt and keep pushing, increasing the surface area.

You are trying to reduce the surface area, and they are trying to push more surface area.

So, you have to keep changing and working to reduce the surface area even as they are trying to increase the surface area. As the opponent, being slow to adapt, continues to direct the push over a larger surface area, they make their push more diffuse. The vectors are going in different directions, and when they meet your single point,  approaching zero pressure per square units of ….surface area.

You are continually reducing the surface area that receives their push, approaching infinite pressure per sq cm. You continually to try to achieve the perfect single point engagement, considering Zeno’s paradox, but confident that you will get close enough for all intents and purposes.

In reality, peng does not actual achieve zero surface area. But it does approach it. 

Psychologically, it means that you seek reduce weight and surface area while the opponent is seeking to increase it. You each have a different strategy from the other.

If you are both trying to increase the surface area, then this is what some famous teachers have called “Bulls butting heads.” 

So, you approach infinite pressure per square inch, going toward them, and they approach zero pressure per square inch going toward you.

And you may ask, “What happened to Newton’s Third Law of Motion?” Well. It still applies. It is simply that their vectors are confused, and yours are not. It is multiple vectors vs a single geodesic.

Of course, if the surface area were actually zero, I suppose the forces would be undefined.

In the illusive perfect scenario, the engagement will be like a mature black hole, simultaneously infinite and non-existent, not a thing but a place in space time, containing entire universes of its own.

*Mind blown. Gives head a shake.*

If the opponent pushes and actually meets zero resistance where they were expecting some, then their brain will experience a momentary programming error, like a computer being asked to divide by zero. 

The real challenge to soft peng is awareness and timing. It does not take much surface area to overcome it, and once soft peng fails,

it may be too late to engage hard peng. If you wait too long to engage hard peng, then it is like trying to build a boat when you are already underwater. This is where conditioning is important. The boat must already be built. If you rely entirely on soft peng, you will be able to successfully push the opponent around with your body in all sorts weird and uncomfortable looking shapes.

I don’t have to line the body up. I can walk toward the person like this. They could push on my chest while I walk like this and they will still bounce off of me.

If you rely on hard peng, you will want your spine to be in a precise alignment. Strategically, there is a middle ground, where soft peng is the preferred quality, but the alignment is preserved in case hard peng is required.

Soft peng doesn’t care what shape you are in. It gives you the flexibility to go into all sorts of weird positions while continuing to engage your opponent’s centre of gravity. and still be manipulating the opponent’s centre. You get to continue being a threat to them while you are defending against their attack. This is an extremely powerful tactical advantage. Your defence is an offence. You are attacking and defending, And their attack ends up pushing them over. So, every time they try to push, punch, kick or throw, it always ends up bouncing back at them. They eventually don’t want to fight anymore, because everything they try to ends up slapping them in the face.

That is the advantage of soft peng.

Hard peng give them too many ways to get away, or to escape.

However, if you don’t have good hard peng, then you really need to be a very good shot. We say, maybe I have a nuclear bomb. But I only use a pistol. The thing about a pistol is that you have to be a very good shot. If you are not, then the opponent will close on you, and then it will be too late for your nuclear bomb.

This soft peng is what the tai chi classics call “the needle inside the cotton.” It means that the peng is sharp, and thin. The opponent must not be allowed to engage with a thick cross section of reaction force. The peng remains needle-like all along that centripetal geodesic.

If it gets thick in any part, then that part needs more bulk modulus. But then the whole structure will begin to collapse around that place. You can do that on purpose and become like a supernova, by collapsing and exploding back outward again. If everything is set up just right, that can work. I’ve done it myself, where I thought the fight was over and then I realized that I was still gathering energy, and then KABOOM! There they go.

Now, you might be asking, “How can you  reduce the surface area of your peng without reducing the surface area of the opponent’s push?” 

That is complicated, and very fun to practice. I would like to show you some of those exercises. But those will have to be in other videos. But developing this skill, will refine your accuracy, efficiency, and the timing of  all your techniques.

If you push on the end of a  needle with your hand, it will pierce your hand. But your hand will slightly dull the needle. How much you are pierced and how much the needle is dulled, will depend on the force applied and the elastic modulus of the two objects. A flat piece of steel will be pierced less and will dull the needle more. As the needle becomes more dull, the surface area increases and the bulk modulus becomes more of a factor.

Likewise, if your opponent pushes and you engage with a single point of contact, that point will be flattened over time, increasing the surface area and involving more bulk. Resisting the push will become more difficult over time.

The solution is to either tense up to increase your bulk modulus or to move in a way that reduces the force of  the push, and change the angle so that they cannot increase the surface area.

Part of the secret lies in the timing of the changing angles of incidence. If the opponent pushes your forearm with their palm, you can engage with every bit of forearm that is in contact with their palm, or you can engage with only a single point, preferably the point most proximal. If they don’t recognize the change, they will continue to push against the non-resistant part of the forearm. 

This means that their push will be instantly diffused, meaning that most of their force will be pushing somewhere other than your centre. They will need a few nanoseconds to redirect to your centre. In the meantime, you will have been able to advance toward their centre. When the opponent corrects the alignment of their push, you simply roll a nanometre or two in any direction and meet their diffused force with a single one-dimensional peng.

The result is that their push cannot gain purchase on your centre, and you can continue to track their centre without meeting any resistance. For you, pushing the opponent it as easy as cutting through fog with a hot knife. For them, pushing your centre is like trying to chase a swarm of bees through a snowstorm with a bull whip.

Part of the effectiveness of peng (hard or soft) relies on the time it takes for a change in the body to register with the attacker’s mind. If the attacker’s push happens concurrent with or subsequent to the change in alignment, and the change is subtle enough, then they cannot recognize that the target has changed.

Peng also has the ability to manipulate the appearance of your structure by messing with the attacker’s frame of reference. The target looks substantial when it is not, leading the attacker into emptiness, the way a matador’s cape leads the bull. This way, soft peng can be effective against long range and weapon attacks, as well. You can use it to manipulate the opponent without touching them.

Understanding the relationship between the physical interaction and the role of the mind is very important, and does not get enough attention in martial art classes. Those who overestimate the importance of the physical are easily tricked. Those who underestimate the importance of the physical might be prone to silly looking demonstrations and embarrassing youtube videos.

An important thing about peng is that while peng responds to the direction of the force, the push can come from any direction. This is because there is no isolated tension in your body that will attach itself to a particular vector of force. If a part of your body resists in a particular direction, it messes with the alignment of the centripetal geodesic. It is like putting a dam or a dike in the middle of a river. Peng is about relaxation and reducing force, not adding to it.

While I might be compressed a little bit by an opponent’s push, I do not use isolated muscles to resist it, and I don’t lean into it. I depend on the inherent structural properties of my superior posture to redirect the forces into the ground. Like the archway in a Roman aqueduct, I let the shape redirect the force in a way that does not strain my body. I don’t use activating muscles to fight back. This means that it the push suddenly stops, I won’t stumble forward.

Likewise, if the opponent pulls my arm, I don’t fight against it with isolated muscles like my biceps or shoulder muscles, and I don’t lean backward. Rather, I settle my alignment so that my anatomy works for me.

This way, if the opponent suddenly stops pulling, I don’t stumble backward like an arrow released from a bow. The normal structure of my body, conditioned by months and years of refining my alignment and conditioning my muscles, tendons, and bones, enables me to withstand greater forces that try to push or pull me.

The best use of is the education of soft peng.

Hard peng creates tension in order to reign in the bulk effect and constrain all the force vectors so that the centripetal geodesic is unbroken. But it does not allow the geodesic to change shape. And because of the structure and alignment of the skeleton and connective tissue, the range of shapes that can hold hard peng are limited.

Hard peng needs the lower back to relatively straight, whereas soft peng needs the lower back to be able to be straight, and change shape.

Hard peng increases weight and pressure, leading to an increasing bulk effect, and creating random vectors of force that can disrupt your balance. Soft peng continually reduces pressure, decreases the bulk effect, and preserves balance by perfecting the centripetal geodesic.

Bulk peng can be used offensively and defensively, as can soft peng. But hard peng is easier to feel and predict, and adapt to. Soft peng is totally responsive, nearly impossible to feel, and, in its highest form, totally unpredictable.

Um. I’m just getting started. Uh. 

I really want to talk about more of the ways you can apply this and the ways that it works with, say, judo and jiujitsu, and or joint locks, or boxing, or grappling, and, of course, tuishou (pushing hands). I also want to talk about the way this affects you psychologically. Peng is not just a physical thing. The skill is transferable into everything that you do. It is your attitude as well as your physical and mental alignment. It is your response to all kinds of things in your life. It gets very very interesting. Well, to me anyway. I hope it gets interesting to you.

I am going to publish this video, after spending a day or two editing it. We will see where it goes. If there is enough interest in the material, I might do some follow up on this idea. I will have to build some apparatus in order to show you how this stuff works.

I won’t be have any training partners for demonstrations – not for a few months. I probably won’t be doing classes in person until the fall of 2021. A lot will depend on the roll-out of vaccines. Once about 90 – 95% of the population has been vaccinated, then we will be able to start getting back to normal. Until then, it is just me and my little room.

Thank you for your support, everybody. I really appreciate the donations, and the subscriptions, and the positive feedback. The emails and the phone calls that I have been getting have been very helpful, and encouraging me to continue with this work. The online videos are not paying the rent, yet. But we are getting there.

Thank you.

Very good. More practice.


The Modulus of Elasticity is the the ratio between the force applied to a material and the amount of deformation and or displacement that happens as a result of that force. 

There are three main kinds of elastic modulus. 

There is the Young’s modulus, also known as the Tensile Modulus, which measures how stretchy a material is. This can tell you how much force is required to stretch or compress something along a line, usually at right angles to the surface area. 

There is the shear modulus, which measures how twistable a material is. That is usually the force moving parallel to the surface area. 

Then, there is the bulk modulus, which measures how compressible a thing is. This can tell you how much force is required to compress an object, or how much negative force is required to expand it. 

When you learn about these things in high school, it may have been simplified for you so you only had to think about these forces in isolation. But in reality, the different types of modulus interact with each other and change with movement. 

For example, if you stretch something, you have to grab it and pull, that means you are applying a shear stress to one surface in order to apply the tensile stress to another. 

Likewise, if you apply a compressive tensile stress, the bulk modulus will become relevant as you apply increasing force over time. 

It is like this ball. If I could push down on it on a single point, the ball gets compressed, and and the amount of force required increases as I continue to compress it. If it is not contained by some other force, it will expand to the sides. But if I put it in a box, the lateral expansion is restricted and it become more difficult to apply tensile compression.

In tai chi, the tensile modulus is called Peng 掤. There are a few homophones that cause a bunch of confusion. 

Péng 倗 means something like, “Wow”. 

Péng 棚 is a shelf or a rack. Martial art teachers will sometimes say, “I am not a shelf” or “I am not a meat hook. Why are you hanging on me.” 

Péng 堋 is something like an archery target, a dike, or a verb meaning to bury a coffin. 

Péng 弸 is a fully stretched bow

Péng 淜 is a suffix used in place names. 

Péng 硼 is boron. But 硼砰 is a “splashing sound” 

Péng 輣 doesn’t mean anything as far as I can tell. I’m tempted to make something up.

Péng 痭 is…well, (never mind)