The ruling on the field is a first down.
An official shall declare the ball dead and the down ended when a runner is contacted by an opponent and touches the ground with any part of his body other than his hands or feet. The ball is dead the instant the runner touches the ground. A runner touching the ground with his hands or feet while in the grasp of an opponent may continue to advance; or if, after contact by an opponent, any part of a runner’s leg above the ankle or any part of his arm above the wrist touches the ground, the runner is down.
The ruling on the field is running into the kicker.
No defensive player may run into or rough a kicker who kicks from behind the line unless such contact:
1. is incidental to and occurs after the defender has touched the kick in flight
2. is caused by the kicker’s own motions
3. occurs during a quick kick or a rugby-style kick
4. occurs during or after a run behind the line
5. occurs after the kicker recovers a loose ball on the ground
6. occurs because a defender is pushed or blocked (causing a change of direction) into the kicker
7. is the result of a foul by an opponent
The ruling on the field is a fair catch.
If a player of the receiving team makes a valid fair-catch signal, and the ball is not touched by a player of the kicking team, the following apply:
1. If he catches the ball, it is dead immediately, and it is a fair catch. If he muffs the ball, but catches it before it touches the ground, it is also a fair catch. After a fair catch, the ball is next put in play by the receiving team at the dead-ball spot (or at the succeeding spot after enforcement of any applicable penalties). See Article 4.
2. If he recovers the ball after it strikes the ground, it is dead immediately, but it is not a fair catch.