Concussion in rugby – cutting edge or just ticking boxes?

Rugby’s introduction of instrumented mouth guards to detect potential concussion has to be one of the dumbest examples of ‘spin’, ‘box ticking’ and doubling down on a dubious idea. From my vaguely informed perspective, this initiative was wrong on a number of levels, so I am going to jump in ‘boots and all’ possibly making some errors that I will have to apologise for later on.

Firstly – these are clever mouth guards but not that clever – well not yet. Last time I checked, instrumented mouth guards could measure some impact forces but not all. They measure linear (straight line) impact forces relatively well, but their ability to sense rotational forces has been reportedly limited – and those are important things to miss. More research is needed, but there is an ongoing debate about the combination of linear and rotational forces that provoke concussions. What does seem clear is that linear forces, of and by themselves, are not describing the whole picture of brain trauma. Unfortunately the manufacturers web site for the instrumented mouth guards used by rugby does not share detail on how things are measured and calculated. So we have to trust that the sampling rate and precision are adequate and table to detect all forces with high levels of accuracy and reliability.

Secondly, it has been known for quite some time that the size of the impact to the head is not necessarily what determines a concussive event. About a decade ago, Kevin Guskiewicz (a leading concussion researcher out of North Carolina) put sensors in American football helmets and demonstrated that while some players were walking away (apparently unaffected) from fairly massive head impacts, others were going down with a concussion from fairly innocuous ‘sub threshold’ head knocks. So it is not merely the size of an impact that counts. Aside from the complexity of impact size, direction and location, there are also clearly significant individual differences around concussion susceptibility – things such as neck strength, skill, hydration, nutrition, and genetics.

I get that World Rugby wants to be seen to be doing the right thing and making their sport safer, but I am not sure why they and their scientific advisors are choosing to ignore the things that are known. Sure they have poured buckets of money into research around instrumented mouth guards and other devices, but the research was right there in front of them – impact magnitude is not the primary determinant of a concussion! I suspect that Rugby might have been shooting for the easy fix and wanting to be seen to be high tech. Cutting edge is great, but cutting edge can just be another way of saying new and unproven! I get frustrated with mindless measurements in sport, exercise, and health. If you are going to measure ‘stuff’ you really must know what and why you are measuring that ‘stuff’.Things that get measured tend to assume importance, and when we do assign importance to a certain thing we risk missing or ignoring the things that really are important. With what rugby has done, we are all now looking for how big a hit is and likely not seeing or looking for some of the other things that may be really important.

As expected Rugby’s ‘experiment’ produced a lot of false positives (players getting taking off for head impact assessments when they were actually OK) – that’s annoying and harms the game. But there will also have been many false negatives (players not getting taken off when they should have been because the measurements had not lit up a warning) – that’s dangerous and will harm the athletes. We still have a long way to go in unravelling concussions and making sport safer, but trying to simply tick boxes and appear to care, lights me up. Rugby’s use of dubious science makes me question the sport’s sincerity regarding player health and safety.

Reference for your interest

Guskiewicz, K.M. and J.P. Mihalik. (2011) Biomechanics of sport concussion: quest for the elusive injury threshold. Exerc. Sport Sci. Rev., Vol. 39, No. 1, pp. 4-11.