Last fall my riding season ended on a trail that I know like the back of my hand. The fault was mine. I was going too fast on an unfamiliar bike and washed out on an off-camber corner covered in leaves. After being ejected over the bars I subsequently bounced through a garden of softball-sized rocks head first. Once the world stopped spinning I found myself left with a twisted ankle, blurred vision, nausea, and a dented/cracked helmet. A visit to the doctor confirmed that I was suffering from a concussion and would need to take a few weeks off from riding or any activity that required physical or mental exertion.
Concussion symptoms include disturbed vision, loss of equilibrium, nausea, sluggishness, headaches, concentration difficulties, behavioral/personality changes or loss of consciousness. If any of your riding buddies fall and exhibit any of these, proceed with caution and under no circumstances should they be allowed to jolt their brain again until after seeing a physician. Just as you would need to let a broken hand heal, you need to let your brain heal. Further impact to an already-injured brain can have devastating results on the long-term functions of that brain.
That said, there is absolutely no shred of doubt in my mind that wearing the helmet protected me from more serious injuries. But the incident certainly caused me to reflect on a piece of equipment that I otherwise don’t think about and the curious spongy goo it safeguards.
As far as kit goes, the brain is pretty complicated. It’s an orchestra of neurons performing symphonies of thought, emotion and physical control that let us participate in social and professional life. Of course, most riders know this and these days seeing someone riding on the trails without a helmet is a relative rarity. But ride long enough, and across a varied enough set of terrain (trails or otherwise), and you will find people astride bicycles with their hair flowing in the wind.
Yes, for adults, wearing a helmet is a choice. And I think it should remain a choice. I’m all for the individual freedom that allows us to weigh dangers and ultimately determine our own risk profile. You will very rarely hear me voice an opinion in favor of legislated forms of self-protectionism, and by no means is that what this is. Above and beyond that, we all know intuitively that wearing a helmet greatly reduces the chances of serious injury so I don’t want to harp on that either. Simply put, I wanted to write a piece that explored bicycle-related head injuries and how helmets can help prevent them.
There is, however, merit to the current rule that kids under the age of 18 wear helmets. The human brain doesn’t reach full maturity until around age 25 and damage during development can impair the path of many higher level cognitive functions. Incidentally, many of those higher level functions (decision-making, problem-solving, planning, etc) are performed in the front half of the brain – the part most likely to hit the ground in a cycling accident.
Given the headline-grabbing attention it has received lately, it is worth mentioning Chronic Traumatic Encephalopathy (CTE), currently the focus of an outstanding $1 billion dollar lawsuit against the NFL. CTE is a progressive brain degenerative condition that results from repeated concussions and smaller (but still damaging) impacts. Specifically, it results from damage to the areas of the brain responsible for memory, awareness, judgment, impulse control, and aggression, and can eventually lead to dementia and/or severe depression. CTE has already been linked to the suicides of several retired NFL and NHL players. As cyclists, we are not subject to the same play in, play out, gridiron impacts that football players are. Critically, though, we don’t know what the safe threshold is for head impacts, or whether there’s even such a thing as a safe level of head impact. We used to think it was just the big hits, then we understood that smaller concussions in succession can cause big problems years later. The news keeps getting worse: recent research shows that repeated sub-concussion impacts in a single season of high school football can create microstructural damage in the brains of teenagers that’s detectable with an MRI. Worry about teenagers, but save some concern for adults; the older you are, the less your brain is able to repair itself. We still don’t know whether isolated concussions can lead to any permanent damage but I’m certainly not waiting around for the evidence.
Of course, NFL players wear helmets when they play, and we wear helmets when we ride. Helmets don’t make you invincible. They generally do a damn decent job at protecting against catastrophic head impacts; serious injuries such as skull fracture, contusions of the brain, or even death. But it is the chronic repetition of low-velocity impacts that may cause repeated stress injuries to the brain that eventually lead to more serious issues. Compounding this is an athlete’s drive to continue competing in next week’s game, race or ride, regardless of whether or not they should be resting to allow the injuries to heal.
This is at least partially, because the characteristics required for a helmet to protect against a high-velocity impact are at odds with those required to protect against a low velocity impact. The physics of it revolve around the compression qualities of the materials the helmet is made of. Simply put, upon impact the cells within the helmet foam collapse and the resistance decelerates the force. At lower speeds the foam does not collapse and the impact is carried through to your skull.
Of course, one could just put in a large layer of soft foam to completely protect against low-velocity impacts, but the depth needed would result in an overly bulky helmet reminiscent of the ones worn in Spaceballs.
It is generally believed that a leading cause of concussion and sub-concussion is rotational force that occurs when your skull is jolted and the much-softer brain tissue slides or jars against the inside of the skull. In a 2013 CBC News article, Dr. Charles Tator, a Toronto neurosurgeon, explained it as follows “The evidence from science is that concussion is more related to rotational acceleration, which in laymen’s terms is really a jiggle of the brain. It’s like the movement of Jell-O in a bowl when you jiggle it,”. That jiggle can cause damage to the brain’s cellular tissue. Many helmets don’t protect against this rotational force and as a result do little to prevent its impact on concussions. This is confirmed by my own anecdotal evidence – even though I was wearing a helmet last fall I still ended up with a concussion (but thankfully the helmet prevented anything worse).
It goes without saying that helmets are a single-serve product. In other words if your helmet absorbs an impact it is time to replace it. If you fall, or drop the helmet or even question whether it’s time for a new helmet, it is time to replace it. As I mentioned, the polystyrene foam compresses to absorb the force from an impact. It can only do this once and a subsequent impact will result in all force being transferred directly through to your skull. This foam also has a shelf life of around five years. It deteriorates with time, and you would too if constantly subjected to salty sweat and moisture. Helmets should be replaced every 5 years at minimum.
The helmet that I wore on that eventful Fall afternoon has lovingly been retired and now sits deservedly on a shelf next to other overly-romanticized sports memorabilia from my past. As I’ve shopped around for a replacement helmet, I’ve noticed that, to their credit, bike helmet manufacturers are responding by improving the protective abilities of their higher-end products. In the next few paragraphs I’ll outline a few of the more interesting innovations I’ve learned about.
The materials used in and shapes of helmets are changing. In addition to the hard plastic and polystyrene foam layers in a helmet, manufacturers are increasingly adding a layer of a Kevlar-like material that reinforces the polystyrene and spreads any severe impact over a larger surface. This effectively lowers the magnitude of force transferred to the skull (think of a blunt impact, rather than a puncture). Even the shape of helmets has begun to change; in general, trail helmets now extend down lower in the rear and often at the temples and provide better protection of the skull from behind.
There are now features to protect against the aforementioned concussion-causing rotational force. The most widely available of these is the Multi-directional Impact protection System (MIPS). In this system, a low-friction layer sits between the shell and the liner of the helmet. When subjected to a rotational/non-linear impact (cycling head impact takes place at 30-50 degree angles) the helmet slides on the low-friction area which has the effect of spreading out the impact over a larger area. Theoretically, this makes the brain less likely to tear at the connective tissue. Take a look at the video below to hear a bit more about how MIPS works:
Another anti-rotational technology is available from 6D, a manufacturer of BMX and Moto helmets. Its system, called Omni-Directional System (ODS), has a series of hourglass shaped elastomers that sit in an air-gap between the two layers of foam underneath an exterior carbon fibre layer. The elastomers provide a secondary softer layer of cushioning and angular suspension that decelerates rotational impact. It seems that this design is currently limited to high-end full-face helmets. The video below demonstrates the 6D ODS system:
Even with the best protection serious injuries can happen on the trail. When I fell, I was fortunate enough to not only remain conscious but also to be riding with a friend. If this hadn’t been the case it could have been hours before anyone had found me. Enter the ICEdot Crash Sensor, a product that works with a rider’s smartphone to call emergency services in the event of a traumatic crash. The ICEdot is a small device that is attached to the helmet without altering the structure or the fit. In the event of a crash it connects with your phone via low-power Bluetooth and uses an app to send your location and other information about the fall. Upon impact the device initiates a countdown clock on your smartphone, and if the clock isn’t turned off before it reaches zero (aka if you’re out cold or otherwise incapacitated) it will notify your emergency contacts and send GPS coordinates of the incident. We live in the future. The video below explains how the ICEdot works.
Helmet innovations aside, when it comes to head impacts, abstinence (from hitting your head) is the only surefire method of prevention. Your brain is a fragile lump of sponge that contains a gazillion interconnected strands that perform important functions in every action you take. While evolution has done a good job of building in a protective layer of bone and other tissue to protect this sponge, damaging the brain is one of the easiest ways for someone to become incapacitated for the rest of their life. In light of this, I don’t mind spending a bit more money to get a helmet with some of the aforementioned extra protection features.
Before I close (I’m a father; allow me a moment of indulgent preachiness) I wanted to touch on the importance of helmet use off-trail. The road is the domain of the car and cars are fast and big. Car/bike collisions account for over 130 reported cyclist injuries per day (and two cyclist deaths per day) in the US. While admittedly a dated statistic, in Toronto there were over 2,500 car/bike collisions between January 1997 – December 1999. Studies have repeatedly indicated that helmets reduce bicycle related head injuries by significantly for bicyclists of all ages involved in all types of crashes (including those involving motor vehicles). Again, I don’t mean to say that helmet use needs to be legislated, I just find these to be pretty compelling stats that speak to the value of wearing a helmet.
While bike helmets are not perfect and you are better off avoiding impacts to the head, they are still a pretty important piece of gear. I think you should wear one. As for my own head, following the demise of my previous trail helmet, I have already picked up a MIPS equipped POC Trabec for the 2015 season. I hope I never get a chance to test it.
Post-script – Thanks to Dr. Graeme Moffat, neuroscientist and general good guy, for serving as technical expert for this article in all matters related to the functioning of the brain.