We overuse the word “focus” in karate, and for this discussion we have had to subdivide it into “internal” and “external” focus. This is the “external” variety.
To transmit maximum accumulated power into the opponent’s center of mass, we have to “aim” every part of our body toward the opponent. You can see this best in this photo of a karateka doing a perfect flying side-thrust kick.
The kicking leg is extended to the point of impact. The withdrawing leg is tucked up under the body, and it too is “pointed” directly at the impact point. The fighter’s arms mimic the legs, lined up like arrows toward that same point. Even his eyes and skull are lined up perfectly to the same point.
This one isn’t quite the same:
When Master Nishiyama explained this, he described three beams of ki energy coming from your body to pierce the enemy. One comes from the “third eye” in your forehead. One comes from your mouth (your breath). One comes from the tanden (below your belly button). You adjust the position of your body until all three beams are directed toward the enemy. If you try this, you’ll find that it brings all of your natural weapons on line. You can punch with either hand; kick with either foot. There’s a sense of readiness that feels like pointing a gun at your opponent.
One of the demonstrations of this principle is to have the student assume front stance, push out a gyaku zuki, and focus down. Have him look directly forward, eyes on the horizon. Smack the end of his fist with your palm, with a fair degree of force. Encourage him to adjust and tighten down until he feels strong. Then smack a couple of times to prove he is ready.
Once set up, have him look straight up, or straight down, or sharply to the left or right, and smack his fist again. Usually the impact of your palm on his fist will visibly shake his body. He may lose his balance and have to catch himself. He can’t focus effectively when his eyes are misaligned with his direction of force.
That's "external focus." Every part of your body and your mind has to be aimed directly at the enemy in order to coordinate the impact of the blow. It isn't enough to just swing your fist.
