If you've been paying even a small amount of attention to motorcycle helmet safety for a little while, then you probably already know that rotational forces are not your friend. Blunt impacts are one thing, but that description alone tells you nothing about multiple other factors that are usually involved in a crash. Things like speed, angle, secondary impacts with other things in the crash zone as the force seeks to dissipate, and so on. In a crash, you have absolutely no say on when your helmeted head stops bumping into, scraping, or flying across objects in its path.
You may have heard some people (whether moto journalists, regular riders, or medical experts) speak about shearing forces on soft body tissue in a crash, and how even good motorcycle gear can still leave riders with skin shearing injuries. The way human bodies are built means that there have always been and will always be multiple factors that gear manufacturers have to consider, design, and test for in order to up the safety ante down the line, rather than simply introducing new styles/cuts/colors for next season.
