Hockey also has an off side rule. An attacking player is off side, if they enter the other team's defensive zone, ahead of the puck. One of the 2 on ice linesmen will "Blow the play dead with their whistle, and a face off will take place ". In a game where professional players are moving at up to 35 kilometers per hour , the on ice officials must also be elite level athletes, to keep up with the action.
Un like the players, the 2 referees and 2 linesmen are on the ice for all of the 60 minutes of a game, although they get to rest during the 15 minute breaks between the first and second periods. Hockey is the fastest form of sport that does not include mechanical devices like bicycles, or engines. It is also one of the most physical sports with extended periods of continual action. Professional hockey players look like long distance endurance runners, lean and tall. In last years Stanley Cup final series one of the players played 4 games with a fractured breast bone. Playing hurt is a part of the game. JIMB.