| >The guy sounds insane. Simple physics indicates that the longer the collision the less force applied will be. The physics involved are a lot more complicated than you think. To give one of many relevant examples: Bicycle helmets are tested purely against linear impacts, where the head hits squarely against a flat surface. This turns out to be completely unrepresentative of real head impacts, which usually occur at an oblique angle[1]. Injuries caused by rotation of the head are by far the most dangerous type, as substantial shear forces can occur within the brain tissue and high torsional forces can be applied to the spinal cord and brain stem. Motorcycle helmets offer reasonable protection against rotational head injuries, because they have a smooth, round outer surface that is highly resistant to abrasion. Unlike motorcycle helmets, bicycle helmets are covered in ventilation slots, are rarely spherical, often feature rigid visors or other protrusions, and have only a very thin outer shell. Because of the shortcomings of standardised testing procedures, a helmet purchaser has no idea if their helmet will offer any useful protection against the most common and most dangerous type of head injury; There is good evidence that many common bicycle helmet designs will exacerbate rotational forces in oblique head impacts[2], leading to the likelihood of no net improvement in safety compared to a bare head over a realistic sample of crash types[3]. [1]http://papers.sae.org/892425/
[2]http://www.bhsi.org/chinstrp.pdf
[3]http://www.sciencedirect.com/science/article/pii/S0001457502... |