Football helmets are designed to prevent skull fracture, not concussions. We need a complete re-design.

19-Oct-2010 14:03 via Tweetie for MacReplyRetweetFavorite

@injuryexpert

Will Carroll

Will is exactly right. How do you prevent concussions with a helmet? From my layman’s understanding of concussions, the traumatic brain injury happens when the head decelerates faster than the brain can handle; when it “rebounds” off of the skull, injury occurs. With this in mind, the goal of modern helmets should be to reduce the deceleration rate of the skull. The focus right now is rightly on football helmets, but I think that it’s just as important in hockey, a sport where information about injuries might as well be top-secret.

Barth, et al. discussed a basic Newtonian model for deceleration back in 2001. A player running nine yards per second [a 4.44 40-yard dash time] who is tackled and comes to a complete stop in just six inches decelerates at over 22.6g (g being the acceleration due to gravity). If you need reference points on just how hight that is, Wikipedia presents examples of typical G-loads. You can argue that no player runs that fast in game speed, but I’d turn around and argue that few players running full speed who are really lit up by a tackler are decelerating in less than six inches.

Let’s consider a few more things, starting around the premise that not all hits are the same. I’m not talking about the power of hits so much as I am the stopping distance for the head. As a player runs downfield, the various parts of his body are all moving at roughly the same speed—close enough that you can consider it the same as the ground coverage speed. When the player gets hit, there are three scenarios:

1. The hit is such that the stopping distance for the brain is even shorter than it is for the rest of the body: the head stops moving while the body rotates forward underneath, usually resulting in the legs “flying out from underneath him”. You would see this mainly when a player is mid-air and the collision hits his upper body, specifically above the armpits. This is almost assuredly going to be a helmet-to-helmet collision. For a mental picture, consider a wide receiver sprinting downfield, jumping in stride to catch a pass, and being absolutely lit up by a DB. The only saving grace for the wideout here is that he will have reduced his ground coverage speed to jump, as the human body can’t maintain full forward speed while accelerating vertically. The football historians among you will be thinking of Darryl Stingley at this point.
2. The hit is such that the stopping distance for the brain is the same as it is for the rest of the body. This is the default assumption people have, and it works in many cases. That said, “body lean” has to be involved, because the hitting force is going to have to be applied to the head, shoulders, or high in the upper body for the neck not to increase the stopping distance by whiplash. For the worst hits in this scenario, you will see people leading with their heads and the players being generally of equal mass and footspeed (momentum) who are both making a stride at the same time they hit. Collisions are about momentum, and if both players carry the same momentum into the hit and have a foot planted when it happens, their bodies don’t get to translate much linear deceleration into rotation.
3. The hit is such that the stopping distance for the brain is larger than it is for the rest of the body. In this scenario, the tackler has hit the player at or below the bottom of the chest pads, planting their shoulder into the solar plexus. Yes, you’re going to knock the breath out of the guy, but as the player’s midsection stops, his upper body will fly forward, greatly increasing the stopping distance for the head, lowering the deceleration.

Considering the above, part of the issue is clearly in tackling technique: “cleaning a guy’s clock” with a mid-air collision or leading with the head results in bad, bad hits. Past technique, helmet makers need to look at the very important “increasing the stopping distance” problem. I think the issue is fairly simple: a bigger helmet with some sort of gel sack that allows the head to move around inside the helmet while maintaining integrity. The brain floats in a volume of cerebrospinal fluid that’s encased by the neurocranium. As the cranium decelereates, the brain pushes CSF out of the way and to the back of the skull; TBI happens when the brain actually impacts the cranium. That said, the natural choice of having the brain encapsulated in fluid, allowing the brain to increase its stopping distance, is a good analogue for what should be done. I propose that an encapsulated gel be used because the force of impact can drive the gel to the opposite side of the helmet, allowing the head to move more than the helmet does in a way that compressive padding alone cannot. The encapsulated gel, of course, would be enclosed by some compressive padding, probably on all sides, for comfort for the wearer and because you want padding there when the gel has fully transferred.

Let’s go back to that deceleration discussed in the open.

• Let’s put a half-inch of the gel inside the helmet and repeat the collison: (-9)*(-9)/(2*0.181*10.73) = 20.9g That’s an 8% reduction, all other things being equal.
• What about a full inch? (-9)*(-9)/(2*0.194*10.73) = 19.5g That’s 14%.
• Heck, why not two inches? (-9)*(-9)/(2*0.222*10.73) = 17.0g That’s 25%.

Let’s now address the objections:

1. Making the helmets bigger just means you’re going to see more helmet-to-helmet collisions. This is true, but reduction of helmet-to-helmet hits is on the NFL and its enforcement, not on the helmet manufacturer. Also, making a bigger helmet could provide for decreasing the forward curvature, making the helmet “pointier” and making it harder for straight-on, face-to-face hits.
2. You’re not going to see full re-distribution of the gel on all hits. Yes, but you likely will on the worst ones, and those are the ones that need it the worst.
3. You’re just making the helmet heavier. This slows players down and makes them tired. I fail to see the problem here.

Let me finish with a couple thoughts on future study:

• Going back to the larger helmet idea, I do think that you could make the helmet more appropriately represent the human skull if you make it overall larger: elongated in the front, with little direct frontal area. A glancing blow to the facemask is going to let the brain take longer to stop; if you can deflect blows from the face to the side, this will improve concussive hits, albeit at the risk of neck torsion and injury as the head rotates.
• Along the lines of designing a helmet fully, you’d want impact data from all sides of the helmet. Can you have a thicker front section of gel and voids along the sides for it to move into? Probably. The issue then becomes returning the gel back to its normal state. I think the easiest way would be a compressed air system, with players seeing an impact above a certain level required to sit out a play while their helmet is restored.
• The above idea indicates that you’d want some form of real-time data on player helmet accelerations. What’s truly concussive? I don’t know. Is a 17g hit okay where a 22g hit isn’t? I don’t know. Much as there’s the baseline test for neurocognitive functions that smart football organizations now require, I think the NFL should be leading the way in real-time data gathering on collisions in order to assist sports medicine and helmet manufacturers better understand the problems that they face. The best testing for helmets is field testing, and that requires real-time gathering.

Let’s be honest: as a multi-billion-dollar industry, the NFL can afford to make these changes and investigate this further, and it should. Why? If football ends up being deemed too violent, parents won’t let their kids play it at the youth level, and the quality of the sport will then decrease as coaching fundamentals will be required at increasingly higher levels. If the quality of play goes down, the NFL probably loses viewers, and that’s bottom line. Viewed otherwise, if the NFL can use its financial success to increase the sophistication and efficacy of helmets, it should do so, as improved equipment eventually is mass-produced down the chain. If youth football becomes safer, more parents will let their kids play, instruction is moved down the chain, and the NFL has a better product as a result. Football is a sport that American kids love and want to play, and the NFL, in seeking the best product possible, should be getting them to learn the game as early as possible. The only way to do that is to make it as safe as possible, allaying parental concerns about their children’s well-being.

[Nota bene: I am an aerospace engineer by education, a systems engineer and project manager by training, and a football and hockey fanatic. Despite being a wide-body, I refused to play HS football because I wanted to walk without pain when I hit 30. I think I made the right choice for me. I mention this only in case Will Carroll links to this and people wonder who the hell I am to be talking about helmet design. I am decidedly a layman, but a reasonably educated one.]

Mom:

So tonight—13 Jul 2010—I just watched the episode of Deadliest Catch where Phil Harris doesn’t make it from his stroke. Of course, Phil died back in February, so we’ve all known that it’s coming to this point, and … you know, it’s good, this celebration of Phil. Sure, it’s hard to watch, but life and death is just all a part of the journey.

But instead, I’m sitting here thinking about you, not Phil Harris. I looked at a calendar earlier, and if I’m right, today is the tenth anniversary of your first stroke. Not the one that liked to have take you from us. No, the one you had on Friday the 11th, which gave you double vision in your bad eye. You went to the optometrist that day to see what was up. I will never understand, nor will I ever forgive, why he or his staff didn’t check your blood pressure that day. I don’t know his name, and I don’t want to know it.

That next Monday morning, of course, is when we almost lost you. Thank God Dad had years and years of waking up early ingrained into him by the Air Force. One of the doctors said to me once that another half-hour later to the hospital and things would have been different. But things went like they did, and you’re still here.

I never will forget Dad calling me to tell me. He called in the middle of the workday, which never, ever happened. I answered, “Hey, Mom!” expecting it to be you. “No, son, it’s me.” The very first thought in my mind was that he’d been laid off/downsized/whatever you want to say when your top tier of employees have gotten too expensive and/or old. I really did think that’s what was going on. That, I could have handled.

I didn’t come up to Jackson until early Wednesday morning, because Dad said it wasn’t necessary and because I was about to start back to classes. It was the toughest semester I had as an undergraduate: propulsion, aerodynamics, aero structures, and labs, all in one semester. The three hardest courses in my aerospace engineering curriculum, at once. I was vice president of student government on campus. I’d been working for Teledyne a little less than a year. I knew it was going to be a hard fall. How hard, well … didn’t know that.

We talked about this last weekend when I was home over the Fourth, how I somehow ground through that semester but barely passed my classes. I was bound and determined that nothing would slow me down in school. Most every engineering student I knew at UAH either dropped or repeated a class, often multiple times. I never did either, and I’m stubbornly proud of that. If I’d had any kind of perspective at all, I would have realized that trying to kamikaze that semester was just about the dumbest thing I could have ever done.

I don’t really remember much of that semester, other than driving back and forth to Jackson all the time. Every weekend, pretty much. Wouldn’t bring a book with me—had things to do. Needed to see about you. Needed to see you in rehab, in PT. Needed to help Dad get the house together so you could come home and be mobile in it. Moved that damn shiffrobe from Aunt Tommie’s house that scarred up the tailgate of my truck. All those things. We did them because we needed you to still be with us.

And you are.

I vented a lot of this on Twitter tonight before I started writing. My friend Paul chimed in. He nearly lost his mother the end of high school. Breast cancer. Should sound familiar. We shared a little bit back and forth, and I realized something: time doesn’t heal this wound. Time doesn’t make it any easier. A lot of days, I don’t think about how I very nearly lost the person closest to me in my entire life, the one who really gets me. But when I do, it hurts. It hurts a lot. You’d know. We lost your dad twenty years ago last month. Twenty years. Both forever ago and yesterday.

Every time I want to be mad that you’re not as physically able as you used to be—just coming on down to Huntsville when you felt like doing it, because I hadn’t been able to come home—or how your difficulty in communicating, especially for long stretches when I want and need to talk to you about something, I just remind myself that I’m so blessed that you’re still here. And every fleeting bit of rage towards that optometrist, I eventually let it go. Every time I think about re-reading that email you sent me late that Friday night, when you clearly weren’t yourself, but I wrote it off to you being upset about the blurred vision, I get angry at myself again. But we couldn’t really know, and we can’t change the past. I wish, I wish, I wish.

True to who you are, you’ve persevered. You’ve made do with what you can do and learned to accept what you can’t. You probably do what you can do better than you did before, just because you can’t do the other stuff like you’d like. You came farther than the PT folks ever thought you would. They’d convinced me that you’d never stand again without assistance, much less walk. They said it would take a lot of work and determination. Well, you showed them. And you’ve been able to support others who’ve had strokes, and family members of those folks. That’s your way, and I wouldn’t expect any different.

Back to Phil Harris: I only ever watched Deadliest Catch in the first place because it came on Fourth of July weekend back in 2009, when I was home and helping you guys kick the tires on the HDTV we got you and Dad for your 40th anniversary. We came across the show quite by accident while Discovery was doing their summer marathon, and we must have watched three or four episodes in a row that night. I ended up really following the show later that summer after I got back home. I came to like Phil in the way that everyone who watched the show liked him: you didn’t always like everything he did, but it was hard to not love the guy for who he was. The marathon was on again last weekend when we were home, and I told you about Phil having a stroke and all that. I didn’t think you were going to watch it at first, but then I realized not long before bed that you were setting the DVR to record last week’s show. I hope you watched tonight. I can’t even imagine the emotions that stirred within you. I have a hard time putting into words what it stirred within me.

I think the lesson I draw from Phil’s life is this: yeah, I can be a crude, foul-mouthed asshole at times. I may not always act lovingly to the people around me. I go off half-cocked. But at the end of the day, I remember who I am and what’s important: fairness, honesty, and how you love your family. Those are lessons that we can learn from some guy on TV, but they’re also the same lessons that I learned at home from you and Dad. [Okay, so I learned to be a foul-mouthed, cranky asshole on my own.] I’ll treasure the values y’all instilled in us boys as long as I’m alive. They’ve gotten me this far, and they’ll get me a lot further.