In most instances when you fall while moving and hit your head, you don’t fall in a straight line. Rather, you fall at an angle, similar to how a tennis ball makes contact with the ground after being hit with a racket. When your head hits something at an angle, it exposes your head to rotational motion, which studies have shown can be more dangerous than linear impacts.
The Mips system in your helmet works as an extra layer that moves slightly when impacted and is designed to help reduce the amount of force from the rotational motion away from the head.
Some helmet testing methods today more accurately reflect real life accidents and account for rotational motion, but most helmet testing methods have remained relatively unchanged for decades. However, thanks to recent scientific advancements and brain injury advocacy, more and more helmet testing methods are including testing for rotational motion. Mips believes that testing standards will change and that all tests will include rotational motion testing within 3-4 years.