Willy, I would disagree about the tracking, but agree that there are very unrealistic notions.
I saw paul vunak land a nice, slow, harmless kick to his sparring opponents face. Such a kick can be incredibly difficult to land against a skilled opponent, but paul pulled it off with seeming little effort, despite his (skilled) opponents best. When asked he landed such a slow kick, he said it was all about the setup: over the course of a few seconds, wherein he lead his opponent with a few steps to force a certain footwork, had intimidated him such that his opponent only wanted to jab from that distance, and then invited a jab off this bad footwork such that nothing could be done to stop the retailitory kick.
He said setting things up like that had become natural to him, and he could recognise these situations and exploit them (or not). Punching or kicking fast isn't necessiary when your opponent does not understand this flow.
This is what I think of when I say leading. It's knowing where their chin will be, not simply seeing it.
Tracking occurs in the few hundred milliseconds it takes the blow to land. A punch probably takes 300-600 ms. Human reaction time is on average 200 ms*. If you're thinking about pulling the punch during this time you can, but only if it doesnt have much behind it. If you're kicking like a thai, good luck stopping. But, those kicks rarely happen unless the striker is confident they will land. If they are unconfident, if they see no wide open defenses, they will throw light blows that can be pulled until an opening for a strong blow presents itself. Very simple.
Aikido focuses in on the heavy blow thrown at the end of this setup process, but it ignores the existence of the setup (which is in fact more important than the blow itself)
"Charley Metro: "The good hitters get their tip-off from the pitchers. And there are many, many ways that a pitcher tips off his pitches. He grips it like that [fingers straight over top of ball]; there's your fastball. When he throws a curveball, he chokes the ball [wedges it between his thumb and forefinger, gripping it on the side so it sticks out]. Now see how much white of the ball shows on a fastball? And how much more white shows on a curveball? . . . Another thing is when they bring the ball into the glove, when they come in with a flat wrist like that, that'll be a fastball. When they turn their wrist like that, it's a breaking pitch. There are many, many ways, and the good hitters pick out these things . . . facial expressions . . . human habits and characteristics will tell."
During the entire middle portion of the pitch, the batter must time the ball and decide where to swing. If the batter decides to swing, he must start when the ball is approximately 25 to 30 feet in front of the plate. The ball will arrive at the plate about 250 thousandths of a second later -- about the limit of human reaction time. The bat must make contact with the ball within an even smaller time range: A few thousandths of a second error in timing will result in a foul ball. Position is important, too. Hitting the ball only a few millimeters too high or too low results in a fly ball or a grounder.
Exactly how humans are able to estimate the expected position of a quickly moving ball is unknown. Obviously, this remarkable skill is learned through long practice. Eye-brain-body coordination is acquired only by going through the motions over and over; even so, the batter misses most of the time. Getting a hit three times out of ten at bat is considered an excellent average. It's interesting that George Schaller and other ethologists have observed that lions and cheetahs are also successful only about a third of the time in capturing their prey."
In reality, it is much easier to punch someone than it is to catch a punch. You see far more throws in aikido class than bloody lips and black eyes, though. It has to be this way, for the most part, attacks must be softened.
To use the batting metaphor for aikido, it is actually more accurate that the pitcher be the attacker, and the batter be the thrower. What's a great batting average? .400? Imagine if for every two throws you had to let someone punch you three times. Hard. Not fun practice.
Thus we pitch scripted punches, and only slightly step things up. To do otherwise (something I strongly advise) requires gloves.
200 ms is about how long it takes you to click a button with your finger when you see something flash on the screen - actual reaction times vary, we are actually incredibly more sensitive in some contexts; reflexes, different senses, different paths of sensation, and differnt brain conditions.
In addition, though we only react with our finegers in about 200ms, we are aware of things that happen in much shorter time periods. A interruption of one's reaction time by 150 ms is a noticably different sensation than a 100 ms delay, or a 50 ms delay, though all are discernable. (thank the psych students for forcing to be their guinea pigs for this knowledge)