Why the rotational movement? In most accidents, a bicycle crash does not happen in a straight line but at a certain angle, just like a tennis ball hits the ground, the head is subject to rotational movement when it falls. Studies have shown that a rotational impact is more dangerous than a linear impact. The MIPS system incorporated in the helmet acts as an additional layer that moves slightly by 10-15mm during impact and helps to reduce the force from the rotational motion, which is deflected away from the head and dispersed throughout the helmet shell.
https://mipsprotection.com/