The classic (yet always impressive) Cool Ki Trick.
(Don't miss out on our strange interactive demo of this Cool Ki Trick! Download the Shockwave plug-in to see it.)
Someone tries to bend your arm when it's stiff, and succeeds. But when your arm is very relaxed, it becomes impossible to bend. This feels very strange. And it's probably one of the best first ways to get a feeling for the correct mind/body state. We try to always teach this to beginners the very first time they come to Aikido class. I remember coming home after my first class and trying to show this idea to my wife. I couldn't do it, but she could. It bugged me for weeks.
How To Do It.
Hold your arm out horizontally, make a fist, and tighten all the muscles in your arm. Now have someone put one hand on top of your elbow, and the other hand under your wrist.
Have your friend try to bend your arm. If he's about as strong as you or stronger, he should succeed.
Now, hold your arm out (again, with just a slight bend at the elbow), and relax all the muscles in your arm. Let your wrist dangle comfortably. Use just enough muscle to keep your arm in the air.
Look ahead in the direction your arm is pointing. Feel as though your arm extends out from you hundreds of feet. Imagine reaching and touching a tree or building that is a long distance away.
Maintain this feeling, and have your friend try to bend your arm again.
When you're first learning this - and all - Cool Ki Tricks, you and your friends should really try to help each other out. You need to try to help each other catch the right feeling. So don't try to bend each other's arms with all your might - at least initially.
Different visualizations work better for different people. Try thinking of your arm as a fire hose, and water shooting out of it. Or, think of yourself as being extremely thirsty and reaching all the way across the room for a cold drink. Or, just extend your arm and keep One-Point.
Don't make your arm completely straight. Put a slight bend in your elbow. And orient your arm so that the thumb side of your hand is up. Remember: Elbows only bend one way! Be careful no one tries to bend your arm a direction it wasn't intended to go.
Try not to get distracted by the person attempting to bend your arm. Just keep your eyes forward, and maintain the image of your arm being very long.
There's one thing more impressive than showing people you can do unbendable arm. And that's showing them they can do unbendable arm. Have a friend first make her arm very stiff and try to bend it. (With some people, you won't be able to. But that's okay.) Then have her relax and encourage her to feel as though her arm reaches out for hundreds of miles. Then test her arm again. This is a real good way to get people to stop thinking you're weird and join you in your mind/body training.
"So, what did I just learn?"
The unbendable arm exercise shows you the power of relaxation and positive thinking. The more you relax your arm, the harder it will be to bend. Of course, you can't just let your arm be limp. You've got to maintain the image of your arm being very long, too. This is the positive thinking part. Relax and believe.