This Sunday, like most, I followed my routine of watching NFL games and keeping up with my fantasy football teams. While I was sitting on my couch watching 220-pound behemoths collide in the open field, I wondered how the motion of these players related to physics.
When it comes to running styles in the NFL, coaches consistently preach “north-south” running instead of “east-west” running to ball carriers. With respect to kinematics, coaches prefer their players focus on the y-component of their motion instead of the x-component. They focus on the differences between distance and displacement. If a first down is 10 yards and solely measured by a runner’s displacement in the positive y-direction, and the vector of the displacement of a runner is 10 yards east and 3 yards north, ultimately they are well short of a first down. Therefore, it is understandable that coaches preach “north-south” running because it allows runners to maximize their displacement in the y-direction, which is most important for gaining yards in the game.
Conversely, offensive linemen tend to move in a different manner. A lineman’s job is to move defenders to create running lanes for the halfback. Because of this goal, the motion of linemen can often have a more prominent x-component, as they are tasked with making contact with a defender and then angling them in either the +x or the –x direction away from the runner.
I wanted to particularly analyze the motion of Marshawn Lynch in his infamous "Beast Mode" run from the 2011 wildcard game between the New Orleans Saints and the Seattle Seahawks (video below). In the video, we see Marshawn Lynch rip off one of the most memorable runs in NFL history. If we look at the play below we can think of the motion of each player as a vector within an x,y coordinate system. We can see that the direction of the blocks from linemen and receivers contains a substantial x-component as they angle off defenders and create a hole for the running back. The vector of the halfback’s motion demonstrates a nearly vertical trajectory, following the “north-south” running style NFL coaches value. Thus, Lynch was able to grind his way to a touchdown by ensuring he runs in the +y direction and maximizes his displacement as he moves forward.