This is an excerpt from Hockey Anatomy by Michael Terry & Paul Goodman.
Strength—resisting or imposing a force—is essential for a variety of reasons and critical to the success of hockey athletes. Strength is required in every battle along the boards, in every stride while skating, in every change of direction on the ice, and in every shot. Stronger athletes won't win every battle, but strength puts them in a better position every time they enter one.
Because strength is the maximum force one can exert on an object, it becomes clear how the stronger athlete has the advantage in a battle along the boards. As two players push against each other on the ice to win the puck, the stronger athlete will move the weaker one as he wishes, if all else is equal, allowing him to win the battle. It may be less clear how strength benefits hockey players in other facets of the game, but if other hockey activities are broken down to the movements required to perform those activities, it becomes clearer.
Skating is a complex activity, but in its most basic deconstruction, it is a series of muscle contractions that generate the force to move the skater across the ice. The stronger those muscle contractions are, the more force they generate and the greater the acceleration of the skater will be. Once again, the stronger athlete has the advantage over the weaker one.
Strength, power, and speed are all interrelated, but it's important to understand the differences between them. Power is the development of force over a period of time. The athlete who can generate the maximum force in the shortest time is the most powerful athlete. This translates into explosiveness on the ice. The more powerful athlete is the more explosive athlete.
Power and explosiveness are beneficial in just about every aspect of hockey as well. When changing direction or taking off for a loose puck, the more powerful athlete will be able to generate his or her maximum force more quickly, which translates to a more explosive first few strides and the advantage over a less powerful athlete. A more powerful goalie will push from post to post faster than a less powerful goalie, allowing him to potentially stop more shots and ready himself quicker, giving him the advantage as well.
A final example of the benefits of power is shooting. A more powerful athlete can generate force on her stick and transmit it to the puck faster than a less powerful one. This allows the more powerful athlete to shoot a harder shot in a shorter time.
Both power and strength are required to generate speed. Speed in hockey is seen clearly in skating. The faster skater has the advantage. Speed is evident in other aspects of the game, however. Stick speed is as important to defensemen, forwards, and goalies as well. Perhaps nowhere is this more easily seen than during the face-off. The player with the fastest stick speed will win more face-offs than his or her slower opponent.
Agility is the ability to perform the required tasks in a coordinated fashion quickly and easily. Agility differentiates a great puck handler from a mediocre one. Agility is required all the time in hockey in other ways, too. Skaters must make coordinated adjustments countless times while moving down the ice. The requirement for agility when skating multiplies while making contact with an opposing player or battling for a puck. Goalies adjust their position multiple times each time the puck is in their zone and often several times during each shot. The more agile athlete will have an advantage in almost all aspects of the game.