A few days ago, Popular Mechanics posted an article on the science behind Bruce Lee's famous "one inch punch." Copied by Quentin Tarantino for The Bride's training (and subsequent "impossible" escape), the punch is launched from point blank range and yet lands with incredible force.
It's a stunt, but it's not less impressive of a stunt than an Olympic record snatch is - a physical task of great difficulty done.
Here is the article itself, and it's worth reading in its entirety.
The Science of Bruce Lee's One-Inch Punch
as is this summary and expansion in The Washington Post.
The article says at one point:
""The first thing we found was that karate experts can punch much harder than normal, untrained people. Which isn’t exactly what you’d call Nobel Prize–worthy work," he says.
But Roberts also discovered that for the karate practitioners, muscle alone didn’t dictate strong punches. Rather, when he used motion-tracking cameras to track the puncher’s joints, he found that strikes that synchronize the many peak accelerations in one complex move—like Bruce Lee’s—were also the most powerful. "
Martial artists can tell you this - it's obvious when you get hit with a trained punch vs. getting hit with an untrained punch.
If you've been taught to punch, the first thing instructors try to teach you is to stop winding up to hit. That windup, the movie-style wind-up and throw, is meant to get some extra distance between the start of your punch and the target. It's a technically easy way to generate extra force, much like running before a jump or springing back before you spring forward makes it easier to jump further gets you power by more easily letting you load up your tendons.
Yet it's much slower and much less effective than a straight drive powered by the entire body. A looping punch looks hard and can be hard, but a straight blast with the body behind it hits with surprising force.
How is it done?
Technique and posture.
The article mainly discusses the role of the brain in firing the entire body in a coordinated fashion. The entire body moves to drill that punch through the board - and you can hear Rampage Jackson discuss this on Sports Science, too. But equally important are the posture of Bruce Lee when he throws and his technique.
This is the secret behind every physical motion, from that punch to a baseball throw to a successful bench press or clean and jerk.
Proper posture ensures there is no wasted motion. His stance is appropriately wide but not too wide - enough to drive off the back foot and start the chain reaction of loaded tensing. His arm is neither too straight nor too slack, so he's only a short distance from the best extension to inflict maximum impact. Hisbody is largely sideways, to increase the drive.
Proper technique ensures the entire body functions as a single coordinated unit. That's the brain's job, according to Popular Mechanics, but it's still a function of training. People talk "muscle memory" but it's all coordination. It's getting your body to connect from one end to the other. As Dan John says, "The body is one piece." Bruce Lee's punch demonstrates that in spades - his entire body moves to make that seemingly too-little distance between knuckles and board all he needs to drive right through it. You want everything in your body acting in the right order, with the least possible hesitation.
When you train, remember you want to get your body in the right posture to do the lift, and then coordinate it all together with proper technique. That is how you can maximize what you lift, and maximize the effectiveness of your body at all forms of sport.