Wednesday, April 21, 2010

How Fast is a NHL Goalie?

In the NHL, saves win games and never more so than in the playoffs. The NHL goalie's quick reactions can mean the difference between a team advancing to the next round of the Stanley Cup and pulling out their Hawaiian shirts for  an early summer.

The shootout is one of the ultimate tests for the goalie. Goalie against shooter, one on one. Shooter tricks vs goalie nerve and reaction speed. Because of this one on one scenario, the shootout is a great way to analyze how fast a goalie reacts.

In the 2009-2010 season, Sidney Crosby of the Pittsburgh Penguins, has been the best shooter in a shootout, scoring 8 of 10 shots. In the goalie stakes, Ilya Bryzgalov of the Phoenix Coyotes has the best record saving 45 of 62 shots for a 72.6% save rate. There are goalies with better saving percentages but Bryzgalov has won the most games (8) with his 45 saves.

Below is some video of the top shootout saves from the 2008/2009 season. What is great about NHL TV coverage is the overhead view of shots on goal. This perspective allows us to easily calculate how quickly a goalie needs to react to make a save in a shootout situation.

To make a calculation of reaction time we will need to know some basic detail about ice hockey and to use some inexpensive or free video analysis software to do the calculations.
The NHL hockey net and goal crease gives us a scaling dimension in the pic below. We know that the goal crease (red block with arc in front of the net) is 8 foot wide and 6 foot from goal line to top of the crease. We can place a grid on top of this goal crease and estimate from this that each block is 6/8 foot wide and 1 foot long.

Now we can look at 2 snap shots of the 2nd save in the video above by Jason LaBarbera.
We have included a time clock along with the grid so we can see how long it takes from shooting the puck until the puck hits the glove and therefore how much time LaBarbera had to react.
We can see that from the moment Schremp makes his move to shoot until the puck is in the glove is 0.5 or half a second. This may be an over-estimation of the time but it will work for our analysis.

With our grid and knowledge of the grid dimensions we can also measure how far the puck traveled over this time. In our first pic we can see the puck is at the bottom corner of the goal crease and in the last pic the puck is in the glove almost on the goal line 0.5 seconds later. The puck therefore traveled 2.5 grid spaces in length and 6 in width or about 2.5 ft in length and 4.5 ft in width. If we use a basic Pythagorean equation we know that the puck traveled about 5.15 feet.

We can calculate that LaBarbera had 0.5 of a second to react to a puck traveling at approximately 10.3 feet per second over a distance of 5.15 feet.

Some video analysis tools make this calculation much easier to do by allowing you to set scaling distances in the video and calculate the distance the puck traveled and even its speed.

The speed of the puck from a slap shot in ice hockey can reach as high as 105 mph, which is 15 times faster than the shot we have just analyzed. However it is not only the speed of the puck that is important for a goalie to make a save. The distance the puck needs to travel and the time available are all important factors. In one on one shootouts it is often the speedy reactions to skilled stick work, that keeps the puck out of the net.

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