The Weekly Warfare   Musings martial from across the SCA

(Ed. This is part 3 of a 5 part series. Comments that indicate a failure to read previous entries shall be mocked and, possibly, moderated with extreme prejudice. The author took the time to do the research, you can take the time to read it)

(See Part 1, Part 2, Part 4)

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In the previous two articles, I demonstrated how the typical amount of force delivered by SCA rapier thrusts relates to the force required to cause a concussion. Importantly, the levels of force delivered against Llwyd’s machine (~15-28lbs) were significantly lower than this threshold (~100lbs). However, we know that concussions do occur from blows delivered in SCA fencing. Consequently, we must therefore conclude that these blows are either delivered with an atypically high level of force, that Llwyd’s machine is not measuring typical blows, or that there are other factors that add to the amount of force delivered in order to reach this threshold. Here we discuss those other factors which include the angle and location of impact, the body movements of the fencers, and the technique used to deliver the blow.

 

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Impact Location and Direction:

The largest factor that determines whether a blow can cause a concussion is where and how it lands. Obviously a blow that doesn’t strike the head won’t cause a concussion, but where a blow lands on the head is also important for determining whether the head undergoes linear or rotational acceleration. As we showed in the first article, far more force is required to cause a concussion due to linear acceleration (~750 lbs) whereas rotation can cause a concussion with far less (~100lbs).

 

As shown in Figure 1, the blows that are most likely to cause rotational acceleration of the head include rising blows landing under the chin, rising blows to the top of the forehead, and cross-wise shots landing on the cheeks or temples. These blows are more likely to cause rotation of the head due to the asymmetrical shape of the head and the placement and shape of the neck muscles that resist this kind of motion. Specifically, the shape of the head means that the face is further from the axis of rotation than the rest of the head, which provides a longer lever arm for blows to act upon. Likewise, the muscles that resist this kind of motion are the sternocleidomastoid which is relatively small and is not directly aligned to oppose this kind of motion.

 

 

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Body Movement:

The second biggest factor is likely the body movement of the fencers. The blows discussed in the second article were measured against a stationary machine under relatively “perfect” conditions. During a bout, fencers are typically moving and they may accidentally put their body behind blows by using poor technique for delivering a blow such as kinetic linking (i.e. throwing a rattan blow), flinging their body forward in their footwork, jumping, or falling (See Figure 3). Importantly it is possible for either fencer (the blow deliverer or the blow recipient) to add force through body movement.

 

The relative contribution of body movement should not be underestimated. Consider how much force is generated by a person walking into a wall. If that person’s mass is 100kg and they were walking forward at a pace of 1m/s (a moderate walk), then we can calculate this amount of force as long as we know how long it takes their body to stop (i.e. the amount of force is reliant on the rate of deceleration). Due to Newton’s third law of motion (When one body exerts force on another, the second body simultaneously exerts an equal and opposite force on the first), when you collide with the wall, it exerts an equal and opposing amount of force on you, which causes you to stop (i.e. decelerate). Therefore, the faster you stop, the harder you hit the wall (Assuming the wall doesn’t move). Consider a relatively slow stop, taking 0.5 seconds; we can calculate the force as F = 100 kg * 1m/s/0.5s = 200N ~50 lbs. In contrast, a relatively fast stop, taking 0.1 seconds, would result results in F = 100kg * 1m/s/0.1s = 1000 N ~250lbs. Based on this, it is easy to see how movements of the body can dramatically increase the force of impact that can occur well beyond the forces measured by Llwyd’s machine.

 

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Punch vs. Push:

Another factor is the temporal characteristics of the impact. The muscles of the neck provide a significant level of protection against concussions because they are able to resist rotational movement of the head. However, these muscles need to constrict in response to an impact, which takes time. Because of this, impacts that cause force to be applied faster are more dangerous than impacts that spread that force over time, regardless of whether the total force or the maximum force is higher in the slower impact. For instance, a “punching strike”, which maximizes impact force is more dangerous with a blunted weapon than a forceful push because the push provides time for the neck muscles to resist the motion.

That being said, pushing through your target is better technique when using a sword. Swords do not rely on their impact in order to cause damage, rather they do their damage as a result of continuing to cut through a target after the impact. Maximizing impact force, as we might do in boxing, is therefore detrimental because it is more likely to cause the blade to bounce off of the target following the impact and it prevents continued penetration with the blade. This boxing video does a decent job of describing the difference between punching and pushing and the reasons that he gives for why a “snapping” is best for boxing and are the precise reasons why they aren’t good for when you’re using a sword.

 

 

Snapping vs. Pushing Punches Video (YouTube)

This test cutting video, while a bit long-winded, provides an example of how this works with a sharp sword. The rest of the video tests out a couple different ways of delivering blows and is worth a watch, but for our purposes, you can skip ahead to the 20:34 mark.

http://www.youtube.com/watch?v=efelZtMbfNk&t=20m34s

 

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Who is Responsible for Controlling These Factors?

 

If we look at the list of other factors listed above, the key take-away is that the person delivering the blow is largely responsible for causing concussions. While they do not have control over whether their opponent steps into the blow, they are in control over:

1. How hard they strike
2.  The placement of their blows
3. The technique used to deliver their strike
4. Throwing their body-weight into the blow and
5. Their own body movement towards their opponent.

We should therefore consider it the responsibility of the person delivering the blow to control their weapon such that they are not likely to injure their opponent. Importantly, punching and flinging techniques, slipping on the ground resulting in hard hits, failure to control distance, failure to cushion blows, throwing cuts as punches, etc are a form of negligence and as fighters and as marshals, we should be proactive in eliminating these from the field.

Fighters who do these things may be quite capable of delivering blows within the typical force range most of the time, however, these techniques make hard, injurious hits more likely because they remove the fighter’s ability to control their weapon and body. When such blows occur, they are not accidents; they are the result of malice, ignorance, or negligence and should be treated as such.

We should also keep in mind that the recipient of a blow has some control over whether or not they will be injured. The recipient has control over whether they step forward without protecting themselves (i.e. closing the line/parrying, etc) and certainly should avoid footwork that involves flinging themselves forward. Recipients can also control how they receive a blow, but it is not strictly their fault if they receive a hard blow wrong. We should actively train fencers to receive hits correctly and fighters who routinely fail to actively receive blows are a danger to themselves.

 

The next article will address specific techniques for both the deliverers and recipients of blows to reduce the likelihood of concussions in SCA rapier.