­Data from the dummy, combined with motion capture of Steve's punch, provides an inside view of devastation.

When Steve's thousand-pound punch lands, it sends the brain sliding inside the skull.

A chain reaction occurs.

The skull accelerates and decelerates rapidly.

But the brain, floating in cerebrospinal fluid, keeps moving.

The brain recoils toward the back of the head, causing trauma from the rear.

It then snaps to the front of the skull, multiplying the damage.

Trauma from both sides.

Neurotransmitters fire.

An electrical storm short-circuits the nerves.

Doctors call it a severe concussion.

We call it a knockout.

Technology confirms legend: the one-punch knockout is real.

But how do they do it?

The secret of boxing is known as kinetic linking.

A perfect flow of energy through the entire body.

Motion capture shows that the punch starts not in the fist, but the feet.

The rear foot drives backwards into the ground.

Like links in a chain, the energy travels up the leg, twists through the hips, and into the large muscles of the back, chest, and shoulders.

Like the coiling and cracking of a whip, the energy multiplies through leverage as it flows through the body, travels out the arm and fist, and snaps into the opponent.

And yes, size does matter; the bigger the puncher, the more mass in the whiplash.