I've never played organized football. When teams talk about making adjustments at halftime, why is it that "at halftime" is the magic time? What prevents similar adjustments from being made during the game? Half time is only 20 mins long, and only part of that time is in the locker room. What prevents the defensive or offensive units from gathering on the sideline and making adjustments during the game? Is it truly a matter of time, and there isn't enough time to talk over adjustments before the group needs to return to the field?