There is a great story told of a tai chi master who was attacked from behind while walking down the street in town. In those days sifus were accustomed to being challenged by accomplished fighters eager to prove their skills, but in this case the master didn't even both to face the attacker. He just let him attack. People were astonished to see the master repel the attacker by doing literally nothing. The challenger bounced off the master's back and left convinced of the master's power.
This tale illustrates the power of the most basic tai chi technique, being rooted. The idea is as simple as it sounds. Just as a tree is connected to the ground through its roots, rooting in tai chi means that your body, your mass, is linked to the ground. To see how powerful this connection can be, imagine bumping into a chair. You get hurt but not that much because the chair moves. But if you bump into a tree, you get hurt because the tree doesn't move. In fact the harder you bump into the tree, the more you will bounce away, like a tennis ball thrown against a wall. Just as the tai chi master in the story must have had some kind of ability to attach himself to the ground, even when walking, the attacker in the story must have been a kung fu master, able to attack real fast and real powerfully, to be bounced so far away.
Being rooted is also the key for the special striking and kicking power we get in tai chi. We call this the attacking power of root. Instead of relying on hand or arm power when you strike, you use the whole body power. And not just the whole body power; the whole body-rooted-to- the-ground power. This aspect of tai chi power is not at all mysterious if you understand the mechanics involved.
The trick is to be stuck to the ground when you strike, which makes your mass very great. Since all the definitions of force and energy in physics rely in part on mass, this makes your attacks very powerful. In each equation (force is mass multiplied by acceleration, F=ma; energy is mass times velocity squared, E=mc2; momentum is mass times velocity, M=mv)speed is important, but you can only be so fast. When you are rooted, though, you draw in on the mass of the whole earth, and your mass approaches infinity. If your mass approaches infinity, then theoretically your power approaches infinity also. You can see this in a train, which is very powerful even when moving slowly because it has such a big mass.
Rooting is also the basis of defending against an attack, although many people misunderstand the application. The story I told of the tai chi master can be a little misleading here because the master's feat did not seem to rely on yielding at all, although yielding is the best use of a good root.
Although they are often confused, being rooted is not being stubborn. The idea is not to prove "no one pushes me around" or that you can "stand your ground." It's stubborn to rely on force to resist force; a good root is a tool for flexibility. You should be elastic, absorbing, bouncing. Rooted with the lower body, the tan tien functions as the handle of the whip, and you yield with the upper body the way the grass bends with the wind. The idea is also to snap back, like the grass, for extra attacking power. This is why it says in the classics, "Root starts in the feet, springs from the legs,/ Is executed through the waist and expressed through the fingers."
Some people who think they understand "four ounces deflect a thousand pounds" don't see that relying on rooting without yielding is relying on strength. One of the most common mistakes in pushhands is relying on being rooted too much instead of yielding. The whole idea about tai chi is yin and yang. Tai chi is yin and yang chuan. Yin and yang means that you are able to move forward, backward, yielding accordingly. If you don't have that kind of ability, "if you don't know how to yield beautifully, turning on the waist, shifting the weight" you just freeze. In the tai chi classics this problem is known as "double weighting," or "becoming stagnant," when you resist a force instead of moving with it. In fighting this makes you extremely vulnerable.
Double-weighting is not yielding enough, but there's also the problem of yielding too much, otherwise known as running away. It doesn't matter whether you're trying to overwhelm or outrun the opponent, you're still relying on speed and strength instead of technique. When you run away you give up the root and position you need for responding, attacking power. You see this in boxing, where they move back and forth by jumping.
If the root is so important and powerful, how does one train for a good root? It can't be separated from tai chi training. A good root depends on a subtle appreciation of the same tai chi qualities as the rest of the art: tuck-in, head suspended, loose, round, connected, and relaxed. The horse stance and other exercises in nei kung are the frame for rooting and flexibility, the tai chi form is the movement, and pushhands is the yielding, responding power. Our practice in cotton slippers on a smooth wood floor teaches good rooting because there's so little traction to rely on. Without the traction, you'll slip if you're not rooted, whereas you can cheat if you have better footing. The only thing better would be practicing on ice.
When you are concentrating on being rooted, you should think of a heavy bag of sand or rice. They are so hard to lift because they sink down when you try to pick them up. That's why a chain can seem heavier to lift than a stick, because the center of gravity keeps changing. In the tai chi classics this is called being heavy as Mount Tai.
You can test your root by having someone try to push you head-on while you're standing in a bow and arrow stance, doing the grab bird's tail or ward off position. If you can conduct the opponent's force into the ground, then he or she will not be able to move you. Finally, confronting muggers isn't the only way to test your tai chi in the subway. You can also try out your root by sinking down with the head suspended the next time you're on a shaky ride.