I’m bringing this post up to the top today. Why? Check out the beautifully produced and well written article at ‘Bicycling’ that reflects all the points we made in our blog post below — in much more detail. While reading the ‘Bicycling’article I was struck by a couple of things; a few quotes:
“…As more people buckled on helmets, brain injuries also increased. Between 1997 and 2011 the number of bike-related concussions suffered annually by American riders increased by 67 percent, from 9,327 to 15,546, according to the National Electronic Injury Surveillance System…
Of course, concussions are more readily diagnosed now than they were 15 years ago…It’s also possible that some of the 149 fewer riders killed every year survived to get lumped into the brain-injury category. But that still leaves thousands unaccounted for. We’re left with this stark statistical fact: The concussion rate among bicycle riders has grown faster than the sport.”
One of the most important concepts in the ‘Bicycling’ article is that rotational force is seriously damaging to the brain — and current bicycle helmets do nothing to protect against this. More, the U.S. bicycle helmet legal standards are now archaic; they have not been updated since they became law in 1999 through the Consumer Product Safety Commission. Ski and snowboard helmets? Near as I can tell, they do not address reducing rotational forces, and most suffer from the same problems as bicycle helmets do in terms of preventing concussions from lower impacts (though a new type of ‘multiple impact’ helmet may be what we need; see more below). It is axiomatic that safety gear is the most important stuff you possess — but could safety gear such as helmets be the most stifled when it comes to improvements? What is going on here!?
As we call for in the blog post below, and the ‘Bicycling’ article alludes to, ski helmet brands are indeed addressing some of these issues. For example, the Giro Combyn ski/snowboard helmet will be available this coming winter of 2013/1014, and other multiple-impact “MIPS” helmets are available for snowsports.
A huge problem exists, however, in that legal challenges are constant. For example, it is difficult to even advertise a new helmet technology because it implies your other helmets without it are sub-standard. More, you can build a better helmet, but it may not test well to legal standards such as European CE because it deals with impacts in ways the CE testing does not evaluate (similar problems with ski bindings, or anything for that matter.)
Original blog post: Some of you are going to hate me for flogging a dead horse. Some of you are going to love the opportunity to rear your stallion and try to kick us into agreement with the helmet crusade. Either way I’ll give you the last word in the comments but I’m taking the bully pulpit for a moment. (Disclaimer: I’m not a physicist or a medical researcher; following is simply gleaned from lots of reading along with attempting to be realistic.)
First, we need to get straight on types of head injuries. To keep it simple (apologies to medical pros), we’ll divide the nuances into two types: Direct injury is a surface bruise, laceration, abrasion or skull fracture. These can include brain injury but not necessarily. The other type of injury is brain damage caused by your grey matter twisting and banging into the inside of your skull when your fast moving head quickly stops moving. In the latter (and sometimes former) case, the result is a “concussion,” simply meaning your brain gets bruised and damaged. Also, we should clarify that in this discussion we’re talking about a moving athlete hitting his or her head on something. Helmets also protect against things like rocks falling on your head, but that’s another subject altogether as it involves properties such as penetration resistance.
Scalp lacerations and surface bruises can be spectacular and painful. Blood. Stitches. But without associated concussion or other types of brain damage they heal with no lasting effects. Ski helmets do a great job of protecting you from such injuries. Even a thick woolen hat offers protection from abrasions and lacerations (though of course no impact or penetration protection).
Concussions are different. Each time you undergo a concussion, you get a poorly understood form of brain damage that is known to be cumulative. Eventually, your brain becomes more prone to concussion at lower impacts, and you begin to exhibit 24/7 brain damage symptoms. These effects are said to sometimes happen after as few as three concussions — even over fairly long periods of time. What is more, it doesn’t take much of a hit to cause a concussion.
When your head hits an object, the likelihood of concussion can be measured in G force of the deceleration. You get a possible concussion at 95 g’s, certain concussion at 150 g’s, and serious injury or death at 275 g’s.
In the United States, ski helmets are certified to the ASTM F2040 standard for snowsports helmets. This article refers to a study where they tried to emulate a real-life skiing accident and measure G forces on a helmet “protected” head. The testing was done as if the skier was moving at 30 kph, 18.6 mph. Such moderate speed is frequently attained by nearly any skier.
During the study, measured force at 18.6 mph was 333 g’s when the helmet/head hit a wooden post. That’s significantly above the threshold for serious injury or death. What is more, G force when the head hit hard icy snow was still up at 162 g’s.
That, my friends, is the problem with most ski helmets. They only offer minimal protection. (More, due to liners that only compress with heavy impact, many helmets offer almost no protection against you receiving a concussion in lower energy impacts.)
So, why? Simple physics is the main reason why it’s tough to engineer better helmets. Put as simply as I can, the G force your brain is going to undergo in collision increases as a square of your speed. In other words, a helmet that definitely protects you at 10 mph needs four times the protecting at 20 mph and fully SIXTEEN times the protection if you’re going 40 mph (not an uncommon speed for good skiers). You can even reverse the math for the study I used, and realize that if you’re moving at half of the 18.6 mph, around 9 mph, you’d have 1/4 the G force (is my math correct?), thus, yeah, that helmet would possibly work when you hit that fence post at 9 mph and got 83 g’s on your brain. Though that still sounds iffy, since the lower threshold for concussion is 95 g’s.
What is more, it is common but misleading to assume that a helmet protects you by spreading out force like hardshell knee pads do. Yes, if a rock falls on your head the helmet needs to resist penetration and subsequently spread out the force. But in the case of hitting something, spreading out the force does zilch to change the deceleration that causes concussion.
Thus, though it is somewhat of a paradigm shift, try to put out of your mind that the shell of your helmet spreading force over your head is in any way protecting you from concussion. The only thing that protects you from concussion is to increase the time your head takes to decelerate. This is usually accomplished by the crushing of foam inside the helmet, or sometimes by a suspension system releasing or stretching. (Recent science is also indicating that twisting forces may contribute to concussion, as of 2013 some helmet makers are attempting to address this.)
Adding insult to “injury,” a hard helmet shell combined with semi-rigid foam liner is especially problematic in lower speed impacts. The hard shell of the helmet distributes force just enough to not crush or break the helmet liner — which is designed to deform under high energy impacts. Where does that “low” impact force end up? In your brain. Damaging your brain.
Conclusion? Wear a helmet if you choose; good ones (especially the MIPS models made for multiple impacts) do offer protection. But even with ASTM certified snowsport helmets the possibility of receiving a brain concussion is very real in even low speed accidents. For example, we know of no snowsport helmet that protects against rotational forces, and most are still not MIPS.
As for helmet evangelism, perhaps the ever constant yammering about wearing ski helmets would be better directed at the Consumer Product Safety Commission and helmet industry to up their standards, rather than applying peer pressure to your friends.
Following is from the study as quoted in the article I refer to above:
A simulation using a 50th percentile male anthropometric device (Scher, Richards and Carhart, 2005) was done of a snowboarder going 30 kph, catching an edge and falling headfirst onto soft snow, icy snow and a fixed object (a 28-cm upright wooden post). This simulation was done to assess the effect of wearing a helmet or not under the three different impact conditions. The helmet in question met the requirements of ASTM F2040. The g-loads to the head-form were measured and the associated Head Injury Criterion (HIC) values were computed. HIC is a time-weighted acceleration measure used widely in the automotive industry to measure impact severity as it relates to head injury. This study found that if the impact is onto a soft-snow surface, both the measured g-loads (under 100 g) and the computed HIC values (less than 220) are well within acceptable limits regardless of whether or not a helmet is used. When the impact was onto simulated hard, icy snow, the helmet reduced the average measured g-load from 329 to 162, and the HIC value from 2,235 to 965. When the impact was against the fixed object, the helmet reduced the values from 696 to 333, and the HIC from 12,185 to 3,299.