While the biomechanics behind the powerful blow certainly aren’t trivial, the punch owes far more to brain structure than to raw strength.
Biomechanical Breakdown
To understand why the one-inch punch is more about mind than muscle, you first have to understand how Bruce Lee delivers the blow. Although Lee’s fist travels a tiny distance in mere milliseconds, the punch is an intricate full-body movement. According to Jessica Rose, a Stanford University biomechanical researcher, Lee’s lightning-quick jab actually starts with his legs.
"When watching the one-inch punch, you can see that his leading and trailing legs straighten with a rapid, explosive knee extension," Rose says. The sudden jerk of his legs increases the twisting speed of Lee’s hips—which, in turn, lurches the shoulder of his thrusting arm forward.
As Lee’s shoulder bolts ahead, his arm gets to work. The swift and simultaneous extension of his elbow drives his fist forward. For a final flourish, Rose says, "flicking his wrist just prior to impact may further increase the fist velocity." Once the punch lands on target, Lee pulls back almost immediately. Rose explains that this shortens the impact time of his blow, which compresses the force and makes it all the more powerful.