The Science Behind Bruce Lee's One-Inch Punch

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The famous martial artist and actor Bruce Lee could knock a man flat with a fist that traveled only one inch. How? William Herkewitz of Popular Mechanics decided to find out.

Lee was successful in part because he had mastered his body in such a way that he could use every muscle optimally in order to bring the greatest possible force to bear under that distance constraint. Herkewitz talked to Jessica Rose, a biomechanical researcher at Stanford University:

By the time the one-inch punch has made contact with its target, Lee has combined the power of some of the biggest muscles in his body into a tiny area of force. But while the one-inch punch is built upon the explosive power of multiple muscles, Rose insists that Bruce Lee’s muscles are actually not the most important engine behind the blow.

"Muscle fibers do not dictate coordination," Rose says, "and coordination and timing are essential factors behind movements like this one-inch punch."

Because the punch happens over such a short amount of time, Lee has to synchronize each segment of the jab—his twisting hip, extending knees, and thrusting shoulder, elbow, and wrist—with incredible accuracy. Furthermore, each joint in Lee’s body has a single moment of peak acceleration, and to get maximum juice out of the move, Lee must layer his movements so that each period of peak acceleration follows the last one instantly.

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And that coordination takes us into the field of neuroscience. Ed Roberts, a neuroscientist at Imperial College London, studied how the brains of martial arts practitioners behaved during physical feats. He found that the activity of the white matter in the brain was decisive:

And when Roberts took brain scans of his study’s participants, he also found that the force and coordination of each participant’s two-inch punch was directly related to the microstructure of white matter—the substance that manages communication between brain cells—in a part of the brain called the supplementary motor cortex. This is important, because this brain region handles the coordination between the muscles of the limbs, which close-range punches rely on. The altered white matter allows for more abundant or complex cell connections in that brain region, Roberts says, which could increase the puncher’s ability to synchronize his or her movements.

So Bruce Lee owes his master feat in part to a beefed-up glob of white matter. But that doesn’t diminish the grandeur of the one-inch punch one bit. Like his muscles, Lee earned his brainpower the hard way, with many years of practice. Roberts says the white matter changes in his study’s participants can be traced to the concept of neuroplasticity—the brain’s ability to fundamentally rewire itself to cope with new demands. The more karate experts practiced these coordinated moves, the more the white matter in their supplementary motor cortex adapts.

-via Glenn Reynolds