Taiji has for the last part of the 20th century till now, has been shrouded in a mystery called, "chi", masters the world over intone, that it is the secret essence of taiji which gives fighters hidden power and form practitioners vital essence and long life.
I will not address the longevity of life and vital essence issue here, save that for another day, but I will address the "secret power" of taiji fighters.
Is it nothing more than simple physics of spring coil power?
Whether you believe it or not, the Chen village always described their chi in terms of coiling or "silk reeling" power, the unfurling dynamics of a compressed and uncompressed musculature and fascia of the legs and torso combined to use the hands and arms like rodeo whips, or to grab and twist with what seems like the power of an electric shock! Bagua Zhang and Xing Yi Quan also use this notion, most of the other major styles of taiji like Yang and Wu do not describe these forces as such, of course this is depending on your shifu(mentor/instructor) or laoshi(teacher/instructor), but most prefer to appeal to the mystery of chi, as it appeals to those who have a sense of wonder and mystery and is a far more lucrative marketing tool than the boring explanation of simple mechanics of physics.
Well if we look at the action of a spring and realize if you are doing your taiji correct in combat you are constantly coiling and unfurling from your legs through your torso and arms otherwise you will find it difficult to enforce peng( expanding force), or exercise li(absorbing/deflecting force).
What is Hooke's Law and what is Spring power?
Imagine you have a piece of straight steel wire about 10cm (4 in) long—something like a long paperclip you've unwrapped. If you pull it with your fingers, it's extremely difficult to stretch it. Coil it around a pencil and with a bit of effort you can make yourself a small but perfectly functioning spring. Now pull or push it with your fingers and you'll find you can stretch and squeeze it quite easily.
Why has this once-stubborn piece of metal suddenly become so cooperative? Why is a spring really easy to stretch and squeeze when the same piece of metal, in the form of a wire, was so reluctant to change shape in the first place?
When the material is in its original form, stretching it involves tugging atoms out of their position in the metal's crystal lattice—and that's relatively hard to do. When you make a spring (as you'll discover if you try bending a paperclip), you have to work a little bit to bend the metal into shape, but it's nowhere near as difficult. As you bend the wire, you use energy in the process and some of that energy is stored in the spring; it's prestressed, in other words. Once the spring is formed, it's easy to change its shape a little bit more: the more windings of metal a spring has, the easier it is to stretch or squeeze it. You've only to shift each atom in a spiral spring by a small amount and the entire spring can stretch or squeeze by a surprising amount.
Springs are great for storing or absorbing energy. When you use a pushing or pulling force to stretch a spring, you're using a force over a distance so, in physics terms, you're doing work and using energy. The tighter the spring, the harder it is to deform, the more work you have to do, and the more energy you need. The energy you use isn't lost: most of it is stored as potential energy in the spring. Release a stretched spring and you can use it to do work for you. When you wind a mechanical clock or watch, you're storing energy by tightening a spring. As the spring loosens, the energy is slowly released to power the gears inside and turn the hands around the clock-face for a day or more. Catapults and crossbows work in a similar way except that they use twists of elastic for their springs instead of coils and spirals of metal.
Here's a chart that shows you Hooke's law in action. You can see that the more "load" you apply to the spring (the greater the force you use, shown on the vertical axis), the more the spring "extends" (shown on the horizontal axis). Hooke's law says the extension (the stretch) is proportional to the load, which is why the lower (red) part of the graph is a straight line. In this region, the spring is elastic: it goes back to its original size when you let go.
However, you can see there's more to the graph than that. If you keep on stretching beyond the blue dot (the elastic limit), you'll stretch the spring so much that it won't go back to its original length. In this part of the graph (shown yellow and red), even a small amount of extra force can make the spring stretch by a lot—it's almost like liquorice or bubble gum. In this region, the spring is no longer elastic but "plastic" (it permanently deforms).
Springs also vary in the way they resist forces or store energy. Some are designed to absorb energy and force when you squeeze them; their coils start off slightly extended and squash together when you apply a force, so they're called compression springs. The opposite happens with extension springs (sometimes called tension springs): they start off compressed and resist forces that try to stretch them. Torsion springs have horizontal bars at their two ends so they can resist something twisting or rotating.
Animation: Compression springs are designed to absorb forces by squeezing together. Tension springs work the opposite way, stretching apart when you apply a force. Torsion springs have parallel bars on the end that stop something turning (or bring it back to its original position if it does).
This is one of the true secrets of taiji coiling or compressing force "storing chi(energy)" and releasing energy "chi" uncoiling or extension of spring force.
I have not given photos of masters doing this I will search for good illustrations, but is true, and is one of taiji's "true Secrets". Keep posted!
There is other elements to the concept of chi in combat such as neurochemical reaction the mind focus the bodies position and limbs on an opponent in such a way that blood which is largely in stasis suddenly becomes activated with negative ions and this electrically charged blood quickly moves through the body to the minds focus to energize muscles like greased lightning or like a well oiled cog and gears to move without friction and send tremendous force where it is needed, this combined with the psychological state of hyper-awareness known as "flow" adds to the mystery and aura of what many call "chi". More on these topics in another blog.
