Preseason is over and, if last night’s game is any indication, we’re in for another season of epic passes and bone-crunching takedowns. More and more, however, there’s been talk of the most serious problem in modern American pro football. It lurks at the backs of our minds during the game, brought to the forefront whenever we wince sympathetically at a hard tackle—you can practically hear the players’ brains rattling around in their skulls. Concussions can be devastating to a person’s quality of life no matter what their profession, but almost no other job involves taking hits the way football does—as evidenced by the memory, mood, and mental health disorders that beset NFL retirees at an extraordinary rate.
 |
| Growing concern over concussions has engineers and physicists scrambling to create helmets that prevent brain injury, rather than just skull fractures or bleeds. Can science take the danger out of America’s favorite sport? Image Credit: Penn State. (CC BY-NC-ND 2.0) |
There’s hope, though—or so we’re told—that science will come to the rescue. The helmets on the field today incorporate some of the most advanced protective technology ever developed, representing the work product of thousands of hours spent testing and modifying designs—all in pursuit of ensuring the players’ safety. Some of the more ambitious designs, developed in light of the recent controversy around concussions, have gone so far as to incorporate deformable struts—a kind of reusable crumple zone. The helmets aren’t cheap (the ones currently in use at the pro level cost around $400 apiece, and the Vicis Zero1, linked above, is closer to four times that much) but you can’t put a price on your brain—and given the salaries associated with the NFL, you’d think they would be willing to shell out if it means imperviousness to the risks involved in headbutting people at a full sprint for a living.
Problem is, no helmet is capable of preventing every concussion. Even with the perfect materials—nanoporous foams, super-elastic shells, whatever you can think of—it’s literally impossible to get around the basic physics of the scenario: going from a full sprint to a full stop over a distance of a few centimeters means extreme accelerations, and extreme accelerations can mean brain damage. Newton’s first law says that a body in motion tends to stay in motion, but here it’s the brain that remains in motion, even when the body around it has come to a jarring halt. When that happens, the brain impacts the inside of the skull, and serious damage can result.
We can mitigate this, of course, with the addition of things like foam interiors for the helmets. These can spread out the change in velocity over a longer period of time, reducing the overall acceleration by a significant amount. In a head-to-head collision, the deceleration starts when the helmets make contact, and there’s a short distance between the players’ heads and their helmets’ point of contact, which is where the heads must come to a stop. If a player is moving at fifteen miles an hour (a typical sprint), and has three inches of “wiggle room” in his helmet (a generous estimate), that deceleration can theoretically be smoothed out so that the player’s head feels a G-force of around 30 g. This is well below the 70-75 g that an NFL-commissioned study postulated as the “concussion threshold”, but more recent medical literature suggests that such thresholds might not be definite…or even relevant. There are so many factors that go into the dynamics of a hit—from angles of collision to individual physiology—that calculations like this are extremely limited in their applicability.
Whether or not there’s a solid concussion threshold, it’s clear that players’ heads are still undergoing dangerous accelerations in modern football. Given that we can’t change their starting velocity, the only real way to tip the equation in a safer direction is to increase the amount of time over which that change in velocity happens. Better materials and helmet design can go a long way toward reducing the trauma of impact, but only up to a certain point—beyond that, the only way to reduce the acceleration involved is by increasing the distance over which it occurs. A helmet that protects perfectly against concussions in head-to-head collisions might be possible, but it may need to be larger than current regulation helmets, so that the point of contact is further from the skull. (Note: I would watch the HECK out of “bobblehead” football.)
But even in my ideal world, where everyone is wearing comically large headgear, you’d STILL have the problem of concussions, thanks to the simple fact that the head isn’t the only part of the body taking hits. If a quarterback gets sacked with a hit to the shoulder, the greatest acceleration is happening near the point of impact, but the rest of the body comes along for the ride. The neck follows suit, and with it comes the head. In this case, it’s the brain that’s staying put while the body moves around it, but the end result is the same—the brain is mashed against the inside of the skull by inertia.
While helmet technology has been improving and will continue to improve, this only protects against one subset of concussive injuries. Even then, high-end helmets aren’t available to everyone—traumatic brain injury is a problem that isn’t restricted to the professional level: teens are fully capable of hitting hard enough to hurt themselves and others, and most can’t afford the kind of safety equipment that protects the pros. There’s no getting around it—in a game that’s about stopping your opponents cold, where players are often incentivized (socially and financially) to hit with the aim of injuring, there’s going to be brain damage, no matter how nice your helmets are.
Knowing this, it’s up to bodies like the NFL to work on reducing the risk to players. Experts have suggested rule changes, like eliminating kickoffs and other aspects of the game that are proven to result in the most injuries. While any substantial rule change—from equipment to play style—would doubtless result in outcry from fans, something needs to happen if we want to avoid sending the message that we value our entertainment more than the health and safety of our entertainers. It’s easy to put our faith in science, hoping for miracle materials to save the day, but that faith would be misplaced. Materials science, for all its wonders, can’t save the players from the game—it’s up to the fans to demand change.
—Stephen Skolnick
Looking for more on physics in football? Check out how scientists are using ultrasound to check for injuries on the spot in Game vs. Brain: New Hope for Detecting Concussions on the Sidelines.