> Impact speed is important to the effectiveness of a collision. That's why they train to maximize this speed. Saying "the speed isn't high" in a context where

> Impact speed is important to the effectiveness of a collision. That's why they train to maximize this speed. Saying "the speed isn't high" in a context where maximum speed is a goal isn't a very good argument for safety. I think you are conflating speed and quickness. Offensive and defensive lines rely on quickness (i.e., acceleration) to beat the opposing team and make a play, while other collisions (e.g., tackling) often involve speed. I am not saying that linesmen should not be expected to sometimes suffer head trauma; I was just noting that how often a player runs into another player is not the only factor.