Man-in-motion
What is man-in-motion in American football?
What are man-in-motion purposes?
Any eligible lateral receiver on the field is a man in motion. It runs along the line of scrimmage prior to the snap. It must stop and face the defensive side of the ball before the center snaps it to the quarterback.
The motion has some purposes. Deception and ruining of the previous defensive plans are the main ones. Defenders created audibles looking on one formation but the receivers trick them. The center snaps the ball immediately and the QB starts a play. Its offensive partners exploit defensive confusion in full matter.
These movements often cause mismatches. For example, the QB may replace the running backs if it sees that the previous one will fail a battle against the linebacker. Or it may increase or descend the number of tacklers, changing the offense power. The other reason is to save receiver’s forces.