Over the last 30 years, improved helmets have all but eliminated fatal traumatic brain injuries from both professional and amateur football. Now a new generation of helmets may reduce concussions too.
Tough but voluntary requirements set by the National Operating Committee on Standards for Athletic Equipment have helped cut brain-injury fatalities in all of football from 36 in 1968 to near zero in recent years. But helmet makers are just now starting to tackle the problem of concussions, caused by jarring accelerations and decelerations of the brain within the skull. “Your brain doesn’t care if it’s going from speed to no speed or from no speed to speed,” says Chris Withnall, senior engineer at Biokinetics, a Canadian company that has conducted helmet studies for the National Football League. “It’s the sudden change in velocity that’s devastating.” Although better helmets have helped bring down the number of NFL concussions from 168 in 2001 to 149 last year, improvements may have emboldened players to flout rules and attack head first, inflicting and incurring more injuries.
Helmets for motorcyclists, bicyclists, and race- car drivers are designed to survive one crash only. Football helmets must take repeated beatings. Polymer foam, which absorbs impact by compressing, returns to its original shape in time for the next play. Adams, a leading helmet maker, uses expanded polypropylene foam, a material that is also incorporated into automobile bumpers and dashboards. Perhaps the most innovative absorbent is in Schutt’s DNA helmet. Called Skydex, it is similar in shape to the halves of a tennis ball placed back to back. Multitudes of these absorbers are then arranged in a grid. Skydex’s compression and rebound characteristics have been customized for applications as diverse as pole-vault plant boxes (where the vaulter launches off) and shock-absorbing decks on Navy SEAL assault boats.
Made of polymer-coated steel or titanium, most face masks inevitably transfer shock to the helmet, and thus the head. The Revolution helmet by Riddell, an NFL helmet maker, attenuates some of that force through rubber grommets built into the face-mask mounts.
The polycarbonate outer helmet is usually one-eighth of an inch thick and has little give. “A stiff shell distributes impact over a wider area,” says Withnall. “It also allows more of the padding to dissipate the impact. Your brain in your skull is like Jell-O in a coffee cup. Hit the cup and everything in there jiggles around. That’s what causes the brain injury.”
The NFL helmet studies have found that players often receive blows to the side of the face mask, the ear hole, or the jaw pad. In response, Riddell designed its Revolution helmet to extend the jaw pad. The company also replaced comfort padding with energy-absorbing polymer foam.
Inflatable cushioning was introduced to the helmet in the 1970s to absorb energy. It did poorly at that task but is still in use to give players a comfortable fit.
Why are concussions so often caused by blind-side hits—the ones you don’t see coming? One possibility, suggests J. J. Crisco, an associate professor of orthopedics and engineering at Brown University, is that when a player does see a hit coming, “he tenses his neck muscles, which essentially ties the head to the body and increases its effective mass. The head and body react more as one big object.” On a blind-side hit, the muscles are looser and acceleration of the head and brain greater. This season, in a study led by Crisco,125 varsity college players at Virginia Polytechnic Institute and State University will strap on Revolution helmets fitted with tiny sensors that measure impact in real time, transmitting data to a laptop computer on the sidelines. “We don’t know if hits that are not injurious individually are injurious cumulatively,” he says. “But we will find that out.”