. Author manuscript; available in PMC: 2020 Aug 6.

Published in final edited form as: Am J Sports Med. 2019 Nov 7;47(14):3498–3504. doi: 10.1177/0363546519882034

Table 1:

Description of Impact Classification, which was performed in a top down approach, as listed in rows below.

Intentional vs Unintentional Impacts	Was the impact purposeful? Did one or more players involved in the impact intend for the impact to occur?
Mechanism³⁴ - Head-to-Head (contact with another player) - Head-to-Body (contact with another player) - Head-to-Ground (contact with the ground) - Head-to-Equipment (contact that can occur against sleds or sandbags in practice drills or goal posts in game sessions)	Determine the initial contact surfaces of the analyzed impacts in which at least one player made purposeful (intentional) impact.
Ball Involvement - Yes - No	Do either of the players within the impact have the ball?
Ball Possession - Carrier - Tackler	Is the player carrying the ball or tackling for the ball?
Player Position⁸ - Back (Quarterbacks, Linebackers, Running backs) - Linemen (Offensive, Defensive line) - Perimeter (Wide receiver, cornerback, safety) - N/A (a player’s position may not be defined in a drill)	Position the player was assigned to at the time of the impact.