It's a simple function in the game, recieving less damage. For those saying it limits their movements and slows down their hitting speed it's not always the case. There is a correct rhythm (right after the blocking animation) to maintain continiously, and doing so will not deteriate hitting speed, although less then a few people can do it efficiently. And for the movement, it stops people stop sprinting yes, but I've come to combine the strafing and block-hitting strategy together. Running to the side of an opponent, jumping and turning off a degree block-hitting, whilst maintaining strafe. Because once you've jumped in that position the speed is kept some the sprint longer then you are using it head-on.