This is a guest article by Martin Höppner. Originally, Martin posted this as a YouTube video, and I asked if I could host the transcript on my website to help preserve the message for posterity and for more easy reference and access in the future. He kindly agreed, and gave the article a little editing before sending it over to me for hosting on the blog.

In this companion article I discuss if and how proper gear can prevent concussions and head trauma in the sports of historical martial arts, reenactment, buhurt and SCA fighting. If you prefer the video format, please check out my video: https://youtu.be/YpQsUHXOSvI

For my analysis I used several scientific publications that you can find in the sources below.

Give me a very short answer!

Unfortunately, there is no consensus. Head protection mainly protects from superficial injury, its concussion preventive effects are limited.

Best practice is to take good care of one another, don’t use sticky surfaces on your mask and blunts (like soft rubber) that prevent deflection, use swords that flex well and are not to heavy and train your neck muscles.

Available masks and helmets for HEMA at the moment don’t really cut it at the moment. Padding’s effect is best for soft and normal blows. Peak impacts should be avoided as much as possible. Okay, that being said, let’s talk details:

What causes concussions?

First, lets briefly talk about concussions. They are mainly caused by head acceleration or deceleration leading to the brain getting compressed by the skull. So, while the head is already moving, the brain does not change its velocity as fast due to inertia – leading it to “bump” into your skull. Other forms of “unfavourable energy absorption” include temporal deformation of the skull – leading to the same thing. Imagine a shockwave traveling through your head, tearing on your brain. Sounds nice, doesn’t it?

Detection and dangers of a concussion

Symptoms of a concussion are often non-specific. If you experience headache, cognitive slowing, emotional liability, amnesia, loss of consciousness, nausea, vomiting and / or sleep disturbances after a shock to the head stop the activity and seek medical attention. The under-reporting of concussions by athletes due to fear of losing time from participation in a tournament for example is an area of great medical concern.

There is still a lot of research to be done about the long-term effects of concussions, but they are associated with changes in mood, behavior, cognition, academic and work function, long-term morbidity, suicide rates, as well as activities of daily living.

Research on protective gear

Unfortunately, there are no empirical studies on concussions and protective equipment specifically for sword fighting. Who would have thought, right? But there are still some clues we can take from research on headgear in Hockey, American football, rugby and even bicycling.

A meta-analysis of 15 studies concluded that while headgear significantly reduces the relative risk of superficial head injuries, it is suboptimal in terms of concussion prevention – as the difference in concussion incidence between the groups wearing headgear and those who did not wasn’t significant. Other studies confirm a small significant effect, so the effect of headgear for preventing concussions and TBI (traumatic brain injuries) is limited.

Limitations of current studies

There are a few things that make the analysis complicated. First: It’s possible that the protective equipment changes the behavior of the wearer. This is called risk compensation: a strategy involving increasingly reckless play by those wearing protective equipment. This would diminish any difference between the two examined groups.

Additionally, research like this cannot be produced within a lab – after all you cannot just randomly recruit a few volunteers, put a helmet on their head… or not… and crash them into a wall. So there might be also selective effects, where individuals who are risk avers in the first place are more likely wear protective gear, exaggerating the gear’s effect.

We also have to differentiate the kind of shock, as it makes a difference if you get hit by a body or by the earth – i.e. falling.

Initial kinetic energy and impulse (the strike)

Oversimplified we can think about it as a problem of minimizing the kinetic energy our head needs to absorb.

As kinetic energy is mass times velocity squared, you can already see that moving at half speed at the point of impact (stopping your blow) will quarter the kinetic energy of any strike. Reducing mass by using a lighter sword or by not driving your thrusts and cuts with your body into the opponent can also have a huge impact.

The balance of your sword has an impact here as well. I won’t tell you anything new that a top-heavy sword strikes harder blows. Just keep in mind that it makes a difference how tightly you grip your sword at the moment of impact for example.

You could also display this by impulse, which is defined as the product of mass times velocity. The conclusions are the same, so I will stick to energy as I find the concept easier to imagine.

The transfer process (the hit)

There are a lot of possibilities of how energy actually can be transferred. I try to keep it simple.

First, if a blow is simply deflected by the helmet, then very little energy is actually transferred into the head. Velocity is a vector or simply put: Speed with a direction. If these two things change less, then less energy was needed for that change.

Helmets and weapons therefore should encourage deflection by design. A rubber safety tip, while preventing penetration, can thus increase the transferred energy to the head if the sword now sticks to the helmet instead of sliding off. The same thing can hold for soft helmet overlays to a degree, which is also one reason why soft headgear in other martial arts like boxing was widely abandoned. Then again, these overlays have other positive effects that make this analysis so difficult. For now, you can keep in mind to use materials that are at least not sticky to present a smooth, hard surface. Deflection is a good thing.

Let’s talk about little energy storages, as I like to think about them. Padding, suspensions and bending swords absorb a part of the energy a strike or thrust transfers to release it at a later point of time. You can think of all three as a spring that gets pushed together to release its potential energy later. The receiver will ultimately reach the same final velocity, but at a lower acceleration.

This can delay the energy transfer process enough to benefit your brain – as the fluid around your brain basically does the same thing already – but it depends hugely on the energy of the impact.  So, for example, if a rugby player strikes the ground head first, there is only so much padding can do. You can think of a threshold you don’t want to exceed. Luckily, tackling head first into an immovable object isn’t something I do in HEMA, but if a blade is too stiff you will definitely feel it in the thrust.

A debate that is going on is if padding or a suspension system is better. From a scientific perspective, they both fulfil the exact same role. Both can be good or bad depending on the quality. In HEMA at least, I would say that most fencing masks are not adequately padded on the inside as they were originally designed for much lighter impacts. A very easy solution might be to just get a bigger size and use your own additional padding or maybe even a scrumcap – but in the long run, I want proper gear designed by experts with these problems in mind.

The reciever

This might not desirable if you want to use your headgear for a long time, but if the helmet deforms slightly, then that’s energy not going into your head. If an overlay in HEMA goes flying off, that’s a good thing. If the helmet slips slightly, causes friction between the padding and your head, you feel the warmth of the portion of energy that didn’t move your head. Of course, in an ongoing fight this might be suboptimal for a lot of other reasons… After all, you should care about all possible injuries.

The weight of your helmet & head matter. No seriously, if the opposing strike has to move more mass with the same amount of input, the result will be less velocity and thus less acceleration. A heavier helmet, a system linking your helmet to your body or a strong neck have exactly this effect. But be aware that a heavier helmet will also compress your spine.

Best practice and call to action

Use reasonable weapons and appropriate behaviour (reflect on your exercises), maximize deflection via non sticky surfaces, use good padding or a good suspension system (best on the inside of your reasonably weighted helmet) and train your neck.

Take care

Martin

Sources

Schneider, Daniel K., Ravi K. Grandhi, Purnima Bansal, George E. Kuntz, Kate E. Webster, Kelsey Logan, Kim D. Barber Foss, and Gregory D. Myer. “Current state of concussion prevention strategies: a systematic review and meta-analysis of prospective, controlled studies.” British journal of sports medicine 51, no. 20 (2017): 1473-1482.

McCrory P, Meeuwisse W, Aubry M, et al. Consensus statement on Concussion in Sport—the 4th International Conference on Concussion in Sport held in Zurich, November 2012. J Sci Med Sport 2013;16:178–89.

Karlin AM. Concussion in the pediatric and adolescent population: “different population, different concerns”. PM R 2011;3(Suppl 2):S369–79.

Colvin AC, Mullen J, Lovell MR, et al. The role of concussion history and gender in recovery from soccer-related concussion. Am J Sports Med 2009;37:1699–704.

Hagel B, Meeuwisse W. Risk compensation: a “side effect” of sport injury prevention? Clin J Sport Med 2004;14:193–6.

Wang SS. Boxing Group Bans Headgear to Reduce Concussions. The Wall Street Journal 14 March 2013.

McIntosh AS, Patton DA. The impact performance of headguards for combat sports. Br J Sports Med 2015;49:1113–17.

Kelly JP. Concussion in sports and recreation. Semin Neurol 2000;20:165–71.

Benson BW, McIntosh AS, Maddocks D, et al. What are the most effective risk-reduction strategies in sport concussion? Br J Sports Med 2013;47:321–6.

Emery, Carolyn A., Amanda M. Black, Ash Kolstad, German Martinez, Alberto Nettel-Aguirre, Lars Engebretsen, Karen Johnston et al. “What strategies can be used to effectively reduce the risk of concussion in sport? A systematic review.” British journal of sports medicine 51, no. 12 (2017): 978-984.

Benson, Brian W., Gavin M. Hamilton, Willem H. Meeuwisse, Paul McCrory, and Jiri Dvorak. “Is protective equipment useful in preventing concussion? A systematic review of the literature.” British journal of sports medicine 43, no. Suppl 1 (2009): i56-i67.

Rabadi, Meheroz H., and Barry D. Jordan. “The cumulative effect of repetitive concussion in sports.” Clinical journal of sport medicine 11, no. 3 (2001): 194-198.

Johnston, James M., et al. “Simulation, fabrication and impact testing of a novel football helmet padding system that decreases rotational acceleration.” Sports Engineering 18.1 (2015): 11-20.