Helmets can't stop brain injuries. It's not a failure of equipment or technology or attention paid, it's a simple biological fact. Our old friend Mark Wilson has a wonderful breakdown of the technologies we have, and how they're simply not and can never be enough.

We've covered plenty of ground about the science of how actual brain injury works, but Wilson looks at how helmet technology is designed. It was originally based around preventing skull injuries, which were a fatal problem in football's early days. But these days, we're also concerned about what's happening to the brain inside the skull. And to that end, we can only do so much:

All helmets work under the same principle. The force striking one's head—acceleration mixed with mass—can't actually be prevented. Physics says that energy has to go somewhere, right? What good helmets do is lengthen the duration of the impact itself (in the hundredths of a second range), reverberating energy through various structures and materials, to smooth a hit from a sharp, high-g strike to a relatively smooth curve of deceleration. Consider landing on a concrete floor or a pile of pillows. Which impact takes longer and which impact hurts more?

That dispersion of force and prolongation of the impact can also be explained as a adding some deceleration before you come to an abrupt stop. Pumping the brakes before you slam into the brick wall, basically. But once you do come to that stop, your brain, which is suspended in liquid, is going to smack against the inside of your skull. That's what causes brain trauma like chronic traumatic encephalopathy (CTE) in NFL players, and it will continue to happen as long as football is played the way it is today.

And that's the only conclusion there is after taking in the state of helmet tech. You can't build a concussion-proof helmet. If the NFL really wants to eliminate brain trauma, it would have to build concussion-proof, possibly collision-proof, football. [FastCoDesign]

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