How many cyclists in the UK were seriously injured last year as a result of rotational movement of their helmet upon impact?
The problem is that despite the large number of studies into bicycle helmet safety, non that I know of have ever found the actual ratio of rotational and linear brain injury. Though the prevailing evidence is that most brain injuries result from rotational forces. As the two forces produce characteristic and distinct injuries it may be possible to differentiate between them in brain scans. In postmortem examinations linear impacts cause cause brain damage mostly at the point of impact whilst rotational injuries are found in multiple locations throughout the structure of the brain.
Current research using corpses has found that rotational accelerations cause brain damage in much less powerful and lower speed impacts than those seen in linear collisions. As a result a helmet that should protect you from a 14mph linear impact will still cause brain damage when involved in 7mph rotational impact.
It is crucial that the real life causes of brain injury are understood so that helmet designers can produce effective helmets. Many researchers have tried using dummies, computer modelling, dead bodies and even live monkeys, but non of this has told us what actually occurs in real life accidents. If an examination of existing injury diagnosis and brain scans could provide useful evidence, it should be done. In truth it should have been done years ago.
9/16" Suntour BMX MP-1000 pedals / 56 tooth TA 6-bolt chainring.(I'm not bothered if the teeth are worn or damaged)