Why Do Hockey Players Get Swapped Out During Games?

One unique aspect of hockey is that it has free substitutions, meaning that players can be swapped out anytime during the game or “on the fly” without a stoppage. This is an important part of the game, as hockey is an incredibly physically demanding sport to play. During a shift, a hockey player will reach on average 85% of their max heart rate, with intense shifts bringing their heart rate to just over 90% of its max. Shifts are short, and players are subbed frequently to ensure that a team always has fresh legs on the ice, and players are therefore able to compete to the best of their ability.
Forwards

Forwards on a hockey team are responsible for scoring the most goals and are racing up and down the ice to try and beat the other team. Due to the high intensity of the gameplay, the average shift time for a forward in the NHL is about 45 seconds. In order to make sure they have ample time to rest before hopping back on the ice, a hockey team has 12 forwards divided into four lines, also known as groups, of three forwards. So, the top line will play for 45 seconds and then come to the bench while the second, third, and fourth lines are subbed in, allowing the first line to rest. The first line is composed of a team’s most skilled players, and they will play the most minutes in a game, averaging around 19:20 over the duration of the hour of play, while the fourth line will play closer to 12:30.
Defensemen
A hockey team’s defense is responsible for slowing down the opposing team in transition and getting the puck out of their zone to start a counterattack. Defensemen typically play longer shifts, closer to a minute, as they have to make sure there is a safe opportunity to go to the bench, not allowing the opposing team to score. Defensemen are divided into three pairs, and while one pair plays, the other two rest. Defensive pairings are also ranked, with the top pair playing on average 22:00 minutes a game, while the third pairing will play around 17:00. Defensemen also play an important role in buying time for their forwards to make substitutions. If you’ve ever seen a defenseman holding the puck behind his own net, he’s waiting for his team to change before starting an attack.
Stoppage of Play
If there is a stoppage of play during the game, it will usually be accompanied by a substitution, as it is a risk-free opportunity to get fresh players on the ice. On this note, goalies can help their team get a change in by freezing the puck, or covering it, stopping play. If they notice their team is tired, they will cover the puck rather than trying to pass it to a player to try and get a fastbreak in. However, one stoppage of play where a team cannot make substitutions is when they ice the puck. Otherwise, this would incentivize teams to throw the puck out of their zone often in order to get free substitutions when they are under pressure and tired from a strong attack.
FAQ
Can goalies be swapped during games?
While goalies usually play most of the game, a coach has the option to switch them out if their performance is lackluster. For instance, if a goalie lets in four goals in the first period, they probably won’t be in net the rest of the game. Goalies can also be pulled on the fly, leaving the net empty and in exchange for another forward, therefore gaining an advantage akin to a power play. This is typically done in the last two minutes of the game when losing by one goal to try and score and send the game to overtime.
What is the longest NHL shift ever played?
The longest shift ever played was by Alexei Kovalev of the New York Rangers, where on February 23, 1994, he played a five-minute shift. The story goes that the right wing’s coach was mad at him after taking a 65-second shift and not subbing when told to; so, as punishment, his coach decided to keep him on the ice the rest of the game. The shift became famous as Kovalev thought he was being rewarded, not punished, and drew two penalties and scored a goal.