(Ice hockey): The comparatively difficult rotation of defensive players to and from the team bench that occurs during the game's second period and any even-numbered overtime periods.

In an ice hockey arena, players are seated on a long bench placed just behind the boards near center ice. From just alongside the playing surface, players quickly jump over the boards to get onto the ice for their next shift, or re-enter the bench area through an ice-level door at the end of a shift.

In most modern arena configurations, and as required by NHL rules, both team benches occupy the same side of the ice. The benches are placed symmetrically, starting a few feet to the right or left of center ice and proceeding along the neutral zone to just past the blue line*. (Opposing benches are separated by a small buffer zone that may contain hallway, a camera crew, or more recently an annoying color commentator.)

```               [bench] . [bench]
/--+------------+-----=-----+------------+--\
|   |            |     =     |            |   |
|   |    .       |     =     |       .    |   |
| [ |            |     o     |            | ] |
|   |    .       |     =     |       .    |   |
|   |            |     =     |            |   |
\--+------------+-----=-----+------------+--/
```

During the game, teams defend the net closest to their bench during odd-numbered periods. The teams switch defensive ends at the end of each period of play. However the teams do not exchange benches between periods. Therefore during even numbered periods, players leaving the defensive zone for a shift change must cross the center red line to reach their team's bench.

Players typically tire after 45 to 60 seconds or so of hard skating, thus shifts are perforce short, and players often execute a shift change "on the fly" while play continues. During a change "on the fly", the extra 30 feet or so of space that a long change requires takes just a bit more open ice and a few seconds more time. To get that time and space the defensive team needs to send the puck deep into the opposing zone. If a tired defenseman, racing to change during a penalty kill, fails to get the puck deep enough, he or she can be trapped behind the power play's offensive rush.

This arrangement can affect the strategy of the team on the power play. That team may use its temporary numerical advantage to bottle the defenders up in the zone, passing the puck around rapidly to try and wear down the defenders. If they succeed in preventing a change, they can press their attack hard late in the power play against the exhausted defencemen. This subtlety of this is often lost on leather lung fans hollering "SHOOT!" as the puck bangs back and forth between the attacking players stationed on the points.

It's no secret, however, that coaches hate watching their team take a bad penalty when they have the long change, and players commiting such an offense are likely to ride the pine for an extended time as punishment.

The worst time for the long change is in overtime, when a bad penalty and an ineffective kill can easily cost a team the game.

* NHL official rules require the benches to be twenty-four feet (24') in length and to seat at least 14 persons.

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