I was appalled by a short video clip of a boxing competition that I saw, once, on Ryan Tubridy’s Late Late Show (a popular chat and entertainment show on Irish television) last night, 10^th December, 2010. It showed the end of a match between two boxers, the victorious one of which was a guest on the show. I presume they were professional, because they were not wearing any head protection. One boxer was noticeably taller than the other. This was the closing sequence of the match and it depicted a relentless attack on the head of the taller boxer by the smaller boxer, which continued unabated until the referee intervened, when the taller boxer appeared concussed.

I am a mechanical engineer and that fact greatly informed what I saw. Technically, the fists and forearms of a boxer can be described as padded hammers. The upper arms of a boxer serve as, what people would usually describe as, hammer handles. Padded or soft-faced hammers are used in order to avoid localized damage owing to high-intensity stress. In the case of boxing gloves, the padding would reduce surface bruising by distributing the applied force over a relatively large area. They would also reduce tearing that might result in blood loss. To be more specific: an unpadded hammer with protrusions (such as the knuckles of a hand) could cause deep indentations wherein the skin and underlying tissue could be damaged by compression or stretched to tearing point; also, any blows that are oblique relative to the target surface could stretch the skin and tissue sideways, causing tearing. In boxing, padding of the hammers reduces the occurrence of gory injuries to the target, and to the hammers themselves. A mechanical engineer or a physicist would know that surface effects are only incidental to the purpose of a hammer.

A hammer is a device to apply impulse. This is a highly technical term, which I will try to explain as straight-forwardly as possible. A hammer has a head that is relatively massive, or heavy; two examples of hammer heads are the glove, fist and forearm in boxing, or the steel head of a blacksmith’s hammer. The idea is that over a distance, known as a swing, the speed of the mass is increased progressively until, just before impacting the intended target, a high speed has been reached. The higher the final speed is, the higher is the efficacy of the hammer. Furthermore, for every doubling of the speed, the ‘efficacy’ of the hammer is quadrupled. The energy that the hammer-head has just before impact depends on the mass multiplied by the square of the speed (i.e. the speed multiplied by itself, as in 2 × 2 = 4 or 3 × 3 = 9. As the hammer makes contact with its target, much of the energy of the hammer is transferred to the target in a very short space of time indeed. As contact is made, a very large force is exerted for a very short period of time: this is what physicists and engineers mean by impulse. The very large force causes the hammer to decelerate very quickly indeed and, if the target is capable of moving, causes the target to accelerate.

Many people are familiar with the collision between a moving snooker, pool or billiard ball and another stationary one of the same mass. The moving ball comes to a complete and sudden stop, while the stationary ball is suddenly accelerated to have nearly the same speed as the stationary ball had. Looking at my own forearm, hand and head, I would guess that the mass of my head is somewhat greater than the mass of my hand and forearm, but, in boxing, the mass of a boxing glove would also need to be added to that of the hand and forearm. It seems to me that, roughly speaking, the human head may be somewhat heavier than the hammer that is likely to strike it in a boxing match. Roughly speaking, the collision is similar to the one just mentioned between a moving and a stationary snooker ball, but the head may not reach as high a speed as the fist had. The head, of course, is restrained by the neck and its muscles. These quickly bring the head back to zero speed, although the sensation for the recipient of the blow is, I’m sure, a very unpleasant one. To summarize the story so far, when the head receives a high velocity hit in a boxing match, it is subjected to a very high force distributed over quite a large area that causes the head to suddenly accelerate to a velocity somewhat lower than the striking glove had, whereupon the neck muscles are called upon to bring the head back to a stationary state as quickly as possible.

My knowledge of anatomy is rather limited and I am not claiming any medical expertise whatsoever. A large part of the skull is filled with the brain, which is soft tissue having an average density that is slightly higher than that of water. The brain is surrounded by and almost floating in a liquid, having a density similar to that of water, which fills all spaces between it and the hard cranium. The small difference in density between the brain and the fluid that surrounds it tells me that the brain is very delicately suspended within the skull. Almost all of its weight is counter-balanced by buoyancy forces. Nature, as usual, is ingenious. The brain is a computing engine and every part of it needs to be fed continuously with oxygen carried in blood that flows through it.

As I understand it, there are various partitions or partial partitions that separate regions of the brain within the skull. The brain is not rigid, but rather is very capable of being deformed. To a casual observer like me the brain appears to be somewhat like a half-walnut in a half-shell. However, the brain does not have the rigidity of the walnut. The laws of mechanics indicate that when a human head is struck in a boxing match it undergoes very high acceleration and deceleration. However, because the content of the cranium is not rigid or firmly held in place, different parts will undergo different rates of acceleration and there is likely to be considerable relative movement within the brain tissue itself or between the tissue, the surrounding fluid and the cranium. Partitions, protrusions, outcrops of bone and orifices, all of which I believe exist, are likely to impact against the soft tissue of the brain and subject it to stresses. If there are parts of the brain that are more- or less-dense than other parts, local stresses would be increased considerably. Perhaps some mechanical extrusion, or local severe compression or tearing of brain tissue can occur. Here I am definitely speculating and guessing.

Coming back to what I believe I saw in the video: I saw the taller boxer’s head being struck repeatedly in very quick succession by high velocity punches and I saw it recoiling repeatedly. I think of a plastic container that is sometimes used for making-up salad dressing. The container has a fixed circular disk inside that has some radial spokes (like those of a wagon wheel). Some oil and vinegar, which have different densities. are put inside, perhaps with a little French mustard and pepper. The container is shaken vigorously by hand for about thirty seconds and the French dressing is then ready. The disk with the spokes helps to break up the fluid and enhances the mixing. The video of the boxing match showed the tall boxer’s head being shaken violently by rapid, repeated impacts from multiple directions. There is no question of the brain being broken-up and mixed like the ingredients of a salad dressing—the human being would be damaged long before that would occur and the referee would have declared the winner. To me, as a mechanical engineer, it is no mystery whatsoever that boxers can suffer horrific brain damage, or death. And, by the way, in my opinion head protection would not make the scenario acceptable: an analogy might be to make up French salad dressing by wrapping the container already mentioned in a very thick tea-cosy—it might reduce the intensity of the shaking somewhat. In boxing, head protection further reduces the likelihood of surface damage, but is inadequate to protect the brain. In my humble opinion, a sport played in such a way that the head of a human being can be abused, as I have seen, is a cruel sport.