Back when I first started officiating football after having played high school and college ball, I had the misconception that a back had to go in motion for about one second prior to the snap. But in reality as long as the back is in motion parallel or away from the oppenent's goal line, there is no set time for him to be in motion. So the back can legally go in motion very close to the snap.
The only reason I bring this up, is because I had it messed up way back then. Just hoping that others don't have this misconception too. Never actually called anyone for it, but when I'd see it... I had a strong impulse to toss the hanky.
Working a University of Iowa scrimmage cured me, back then they often had the back go in motion about a quarter of a count prior to the snap. Yeah, I know... those were the dark days for Iowa football.
