Yet most hits to the head, whether they’re from falling off bicycles or scooters or from team sports collisions, do cause the brain to rotationally accelerate. It’s just that the linear acceleration is more strongly associated with severe injuries, like cracked skulls, and when the National Operating Committee on Standards for Athletic Equipment was formed in 1969—a year in which 38 Americans died playing football—the goal was to develop helmet standards that would mitigate only the most severe injuries. And as the Snell Memorial Foundation, a nonprofit helmet safety organization, explains, “manufacturers will design and build to the standard, so that helmets will provide no less than what is required, but they will not provide very much more.”
Helmet manufacturers are constrained in certain ways that make it hard for them to improve their designs, too. Consider the standards set for bicycling helmets by the Consumer Product Safety Commission. As Bruce Barcott explains in an eye-opening investigative feature in Bicycling magazine, since people bike in different climates and conditions, the CPSC mandates that bike helmets have to pass drop tests from a height of 6 feet at temperatures as high as 127 degrees, as low as 1 degree, and after being immersed in water for up to 24 hours. Few materials can maintain their performance in such a range of conditions; one that does is expanded polystyrene (EPS), which is the foam that comprises the inner liner of most bike helmets sold today. The problem is that EPS is so strong that it doesn’t protect well against low-energy concussion-inducing impacts. (A few helmet companies have come up with designs that don’t use EPS, Barcott says, but most are made in Europe and have limited distribution in the U.S.)
Let me explain. In the event that your daughter flies off her bike and hits the ground head-first, her helmet will do two things. First, the outer helmet shell will spread the force of impact over a greater surface area, lessening the blow to the part of her head that hits pavement. Then the inner EPS foam liner will crush, increasing the amount of time over which the force is applied to her head—what Barcott describes as “slowing the blow.” The problem, he says, is that EPS only begins to crush under very large forces; it doesn’t deform in response to the less severe impacts that typically cause concussions, so in these crashes it doesn’t do anything helpful. Ideally, what manufacturers want is a foam material that can deform and protect the head in both high- and low-impact crashes. But given the testing constraints—the fact that this material also has to perform reliably at such a range of temperatures and conditions—companies can’t really use anything else. Activists are pushing to change some of the CPSC standards, Barcott says, but it’s unclear whether they will succeed. Yet considering that kids typically travel more slowly than adults do and are closer to the ground when they fall, kids’ helmets should be designed to mitigate these lower-force impacts.
So kids’ sports helmets aren’t a panacea, at least not yet. That doesn’t mean that our children shouldn’t use them—again, they do protect against the most lethal skull-cracking injuries. So if your kid is doing something that has a reasonable chance of ending with her smacking her head against an object with some force—a puck, the ground, another person, a wall, a car—a helmet is a good idea.
Some final pieces of advice: Make sure the helmet fits. In a 2003 study, pediatricians asked families to bring in their kids’ helmets during check-ups to assess them for fit and found that 96 percent of them were either in inadequate condition or didn’t fit properly. They typically rested too high on the forehead or the helmets moved around too much on the kids’ heads. This video from Safe Kids Worldwide can help determine proper helmet fit.
Also, don’t assume that if your kid wears a helmet, his head is going to be safe. You’ve got to use common sense too. As Nicholas Day pointed out in a 2011 Slate article on why he won’t make his kids wear sledding helmets, head injuries are to some extent avoidable with good parental decision-making. “What's called for are more common-sense instructions from parents to their kids, not another layer of padding,” he writes. Don’t let your kid sled near trees or roads or tons of other people. Don’t let your kid bike or use a scooter or skateboard in busy traffic. Speak up if your kids’ coaches are making them do risky practice drills that involve head collisions, or if they are allowed to head the ball when they play soccer: the American Youth Soccer Organization encourages coaches to not teach or practice heading to kids under the age of 10. Finally, if your kids play sports in which head injuries are common—these include football, soccer, hockey, rugby and basketball—you might put them on a neck strengthening regimen, because “to the extent that you can see a hit coming and you can tense the neck muscles, the head is not going to be moved out of position as much,” Cantu says.
Obviously you can’t protect your kid’s head from everything—hell, my 3-year-old bonked his trying to get off his tricycle a few days ago. Nor would you want to, really, as over-protective parenting is not without risks itself. But given the growing medical concern over the dangers of repeated concussions, common sense says that we might be wise to keep our kids’ heads from smacking into things more than they absolutely have to. Helmets don’t clear us of this responsibility.