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The Ice
One of the most unique aspects of hockey is the
surface on which the game is played: the ice itself. The players talk about the
quality of the ice; they've helped coin the terms "fast ice" and "slow ice."
Scientists, on the other hand, are still studying the chemistry of the ice. In
just the last few years, there have been major discoveries which have changed
our understanding about the nature of the ice.
Fast Ice and Slow Ice
Anyone who has watched a hockey game on
television has heard the announcers use the the terms "fast ice" and "slow ice,"
or even "good ice" and "bad ice." What's the difference? Fast ice is harder and
colder with a smoother surface, while slow ice is warm and soft and may have a
rough surface. For the players, the difference seems to be that "fast ice" is
less "chippy" and there is less "snow." Passing and skating are easier when the
ice is "fast." The quality of the ice differs during the course of the game and
it even changes how teams play the game. Sharks defensemen Doug Bodger told us,
"At the end of periods when the ice tends to get 'snowier', and the puck tends
to bounce a little bit, you might not try to 'stick-handle' as much-you might
just try to get the puck out the zone." In other words, players tend to make a
safe play rather than a finesse play when "slow ice" or "bad ice" conditions
exist.
Oh, Canada
Certain arenas seem to have better ice than
others. Bodger thinks the difference is the hardness of the ice. Rinks in Canada
are well known for the quality of their ice. Edmonton in particular was
mentioned by Bodger as having fast ice. Why is the ice so much better in Canada?
One of the differences may be climate. Bruce Tharaldson, the ice maker at the
San Jose Arena, cited deliveries to the arena as a concern. Opening the delivery
doors of the arena and letting in heat and humidity is a problem in San Jose,
California. This is not as much of a concern for a rink in Edmonton, Alberta,
especially in the middle of winter. Apparently, the freezing and refreezing of
the ice brings impurities to the surface.
Keeping the ice cold is one of the
keys to maintaining fast ice. Bruce Tharaldson keeps the temperature of the ice
at sixteen degrees Fahrenheit (-9 centigrade) for hockey and twenty-two degrees
(-5.5 centigrade) for figure skating. Apparently, the figure skaters prefer
softer ice for their landings and the six-degree temperature difference provides
that.
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Skating
To be in the NHL you need to be, among other
things, an exceptional skater. The players and coaches seem to agree that to be
an effective skater, you need a combination of good technique and physical
strength (although individual responses differed as far as which was the more
important quality). The scientists in this section help break down the mechanics
and physics of skating. Our exploration starts with the interaction between the
blade and ice surface.
Slippery when not wet?
The nature of ice was examined in "The Ice"
section--including the latest findings by chemist Gabor Somorjai. This new
information about ice changes the way we look at skating. For a number of years
before Somorjai's research, there was a debate as to whether pressure or
friction created the water lubricant that was believed to be required for
skating. Most scientists seemed to think that it was pressure. According to
Somorjai's findings this is not the case. So what do you skate on? Well,
actually you skate on vibrating molecules.
Professor Somorjai and his team used new
methods developed in the last 10 or 15 years to examine the surface structure
and composition of the atoms and molecules that make up the ice. These
techniques were developed for high-tech applications--like studying the surface
of materials that can be used for magnetic disk drives, for example. Somorjai
used these same methods to examine ice. What he found was rather surprising.
Somorjai told us, "the structure we determined was an almost impossible
structure, indicating that every second water molecule on the surface was
missing. Since that was not possible, we decided to go back and understand why
[this was the case]." After further study, Somorjai's team found that the
"missing" water [or ice] molecule was indeed there-- but it was vibrating so
rapidly that it was invisible to the technique they were using. Once Somorjai
and his team found this out, they could change the conditions to further study
these molecules.
Up and down
After further study, Somorjai found that these
molecules behave like a liquid, but they only move up and down; they do not move
from side to side on the surface of the ice. This is an important distinction.
If the atoms moved side to side, the "liquid-like" layer would literally become
liquid (which is what happens when the temperature rises above 32 degrees
Fahrenheit). This "liquid-like" layer is thought to be what makes the ice
slippery.
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The Gear
Carbon-graphite sticks, aluminum shafts, and
fiberglass/kevlar goalie masks are a few of the technological advances that have
changed hockey gear, and consequently the game itself. In the game of hockey,
the gear is uniquely personalized and meticulously prepared. The gear, like the
players themselves, is placed in a hostile environment and receives a lot of
abuse. Players, equipment managers, and scientists talk about the sticks,
skates, pads, helmets, and other gear that help protect players and play a role
in the game itself.
The "Hollow-Grind"
Everyone knows that skate blades are made of
steel. What most people don't know is that the surface of the blade is not flat,
but concave. A process called hollow-grinding carves out the center steel in a
blade and produces two sharp edges. These edges give players the ability to dig
into the ice--to stop, start, or change direction.
More on the "Hollow"
Each team's equipment manager is responsible
for sharpening the team's skates, and even the referees' skates during a home
game. Sharks equipment manager Mike Aldrich took us through the process. The
skate--consists of a boot, the blade holder, and a steel blade, with the holder
attached to the boot with rivets. Once the skate is assembled it is taken over
to the sharpener.
The sharpener has a rotating stone wheel that
creates the "hollow." The stone wheel itself is first shaped with a diamond tip,
then the skate blade is passed over the stone a couple of times to identify the
exact center point of the wheel. Once the center point is established, the skate
blade is passed over the wheel a number of times, each time becoming smoother. A
final pass is made with a light coat of oil to give the blade a polish and to
remove any excess debris. The skate then gets a couple of passes with a hand
stone and then it is wiped clean with a cloth.
Each player has his own personal preference as
to how much hollow he has in his skates. Goalies, for example, like less hollow
in their skates. This makes sense since they need to move quickly from side to
side, and a deeper hollow may cause an edge to catch in the ice. Each player
also has his own preference as to how often his skates are sharpened. Some
players may go a couple of games between sharpenings, while others may even
request that their skates are sharpened between periods. Occasionally, a player
will even change the depth of his hollow depending on ice conditions.
Losing an Edge
When these edges get dulled, players will sometimes have their skates come out
from under them. This phenomenon is called "losing an edge." A variety of
factors can contribute to losing an edge. Sometimes the skate blade will come in
contact with sand or dirt in the bench area or with a goal post. Most commonly,
the skate comes in contact with another skate blade, during a collision or rough
play near the boards. Players usually don't realize their blade has been dulled
until they try to make a sharp turn or a stop and find themselves sprawled out
on the ice.
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Making Saves
Hockey goalies have one of the most challenging
occupations on the planet. Imagine trying to stop a six-ounce piece of frozen
rubber traveling at speeds in excess of 100 mph (160 km per hour). Or wearing 50
pounds (22 kg) of equipment and losing 5 to 7 pounds (2-3 kg) of your own body
weight in just a few hours during a game. Goalies do all of these things and
more. Reaction time, mental preparation, and other facets of life in the net are
examined by players and scientists in this section.
Fractions of a second
Goalies have many unique qualities, one of
which is excellent reaction time. In a game where the puck travels at high
speeds, the difference between a goal and save can come down to milleseconds.
How do you develop reaction time? Is it something you're born with? "I really
don't think that you take anybody off the street without some prior God-given
ability," Sharks Goalie Kelly Hrudey told us. The Exploratorium's Director of
Life Sciences, Charles Carlson seems to agree, stating that reaction time is a
"genetic trait." However he believes that you can improve your ability to react
through practice since it is also a "memory function." Reaction time depends on
both genetics and training.
Saves
Goalies make several different types of saves depending on the situation.
Stick-saves, glove-saves, blocker saves, and kick-saves are all part of the
hockey vocabulary. Which type of save does a goalie employ? The answer seems to
be that when he only has a fraction of a second to stop the puck, he uses
whatever part of his body or equipment is closest. If you watch a goalie's save
closely. you'll see that if he's in position he'll need to move only a very
small distance to stop the puck.
Reaction time
In a high-speed sport such as hockey, players'
reflexes are of supreme importance. A player's reaction time can often determine
the outcome of a game. A notable example of this is the reaction time of a
professional hockey goalie. Many a fan of the game has watched in bewilderment
as a goal keeper's limbs are flailing about saving pucks left and right. It's
amazing that most most of the games remain relatively low scoring after watching
powerful players rip 90-mile-per-hour (144 km per hour) slapshots at the goal.
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Shooting The Puck
"How do you hit a puck 100 miles per hour?" was
one of the first questions we asked when we began to examine the science of
hockey. The slapshot is certainly one of the most exciting aspects of the game,
and when properly implemented, the puck becomes the fastest moving object in any
major professional team sport. Players talk about what goes into slapshots and
wrists shots, and the scientists in this section will examine the physics behind
shooting the puck.
Slapshots
Every year before the NHL All-Star game
players' slapshots are clocked with a radar gun. The San Jose Sharks have
arguably the fastest slapshot in the league in defenseman Al Iafrate. He has
been clocked at well over 100 miles (160 km) per hour. So how does he hit a puck
that fast? Where does the power come from? Defenseman Doug Bodger believes that
a good slapshot is mostly technique and that the power comes from a weight
transfer. The weight of the player transfers from his back legs right through to
the stick in his hands.Using a high-speed video camera we examined Sharks
forward Jeff Friesen's slapshot and found that this was true, but there was more
going on than just that.
Friesen hit the ice a good foot or more before
the stick came in contact with the puck. This caused the stick to "bow"
considerably. When the stick did come in contact with the puck, the "bow" was
released, snapping the stick towards the puck just as Friesen was following
through with his swing (and transfering his weight). The overall motion is
combined with the stick snapping back, releasing energy into the puck. There is
also a slight snap of the wrists at the end of the motion--allowing the puck to
spin off the stick. This gyroscopic action allows the puck to remain stable in
flight, which helps the shot's accuracy
Breaking your stick
Just how strong is a hockey stick? After
watching Jeff Friesen's stick bend we wanted to see what takes to break a hockey
stick. In the Exploratorium shop, we used a vise, a spring scale, and a block
and tackle. The particular model we used was a fiberglass stick with wooden
replacement blades. After placing the stick in the vise we pulled on a rope
connected to the block and tackle and the spring scale. To make a long story
short, it took nearly one ton of force to break this particular hockey stick!
Anyone who watches the game knows that players' sticks are broken often. In
fact, most players tape up three or four sticks before a game just to make sure
they have enough.
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Checking
Checking is what makes hockey a "collision
sport" as opposed to "contact sports" such as basketball. The game of hockey is
rivaled only by football as being the most physical professional team sport.
While the object certainly isn't to "tackle" the opposing player, physical
checks slow down, take out, or otherwise affect the opposition's ability to play
the game. The players we talked to had different ideas about what makes an
effective check and we couldn't help but try to find out just how much energy is
released in a check.
How to check
Checking can be defined as using physical force (without breaking the rules) to
either gain possession of the puck or to disrupt the opposition's play. When we
interviewed Sharks players about checking we were somewhat surprised by the
variety of the responses. Each player seemed to have a different take on what
makes a check an effective one. All of the players felt that body positioning
was important. Sharks Defenseman Doug Bodger stressed it and the relationship
between where he and the opposing player were on the ice. Apparently, there is a
great deal of danger in throwing a check--it's not that you can get hurt
(although that is always possible) but rather that you can get burned by putting
yourself out of position. Sharks Forward Todd Ewen's concern was in keeping the
stick and his hands down. The object of a check is to take another player out of
the play or make him cough up the puck, but you don't want your team to wind up
a player short because you're in the penalty box.
Stick-checks, poke-checks, back-checks
When you think about checking, you think about
crushing hits against the board or open ice hits that send players flying
through the air. While those types of hits are certainly checks, there are other
more subtle types of checks. Poke-checks or stick-checks are when a player uses
his stick to "poke" the puck away from another player. Sometimes goalies will
use this technique to stop players who are trying to come around the back side
of the goal. Back-checking is when a player (usually an offensive one) comes in
behind the opposing player to get into the play. This situation usually occurs
after a play is broken up in the opposition's end, a breakaway situation
develops, and the players rush to their own end to get back into the play
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Hockey Fitness
The demands of the game of hockey, along with
an 82-game schedule, take their toll physically and mentally on the players. How
do players stay fit and focused during the season? How do they protect
themselves from injuries? We talked to the Sharks team doctor, conditioning
coach, and the players themselves. We looked at getting fit and staying that way
through the season.
Holding your breath
Most of the players work hard in the summer.
Long gone are the days when a professional hockey player could just take the
summer off. Weights, bicycles, running, inline skating --players do whatever it
takes in the off-season to stay fit. Sharks Defenseman Doug Bodger told us that
while they work hard all summer, the demands of the game itself are more intense
and it takes a while for everyone to get to point to where they feel comfortable
physically. So just how intense is it on the ice? Bodger told us, "I don't think
you're breathing half the time. You're mostly exhaling...pushing and
shoving...and concentrating so much you don't think about breathing at all.
That's why we can only stay out there for a minute at a time. It's like holding
your breath."
Crash Diet
During the course of an average game, some
players can lose as much as 5 to 8 pounds. This loss is mostly water, so players
are concerned about making sure they keep enough fluids in their bodies.
Goalies, who make it to the bench much less often than other players (who have
one-minute shifts), keep a water bottle on top of their goal. Goalies can lose
as much weight as a forward or defenseman. The water bottle on top of the net
has become a part of the game. Occasionally it will move when a goal is
scored--this has been used more than once by replay judges and announcers to
help determine whether a disputed goal should count.
Some players lose more than just water. Many
players will lose weight during the course of the season. In an extreme case,
Sharks Captain Todd Gill went from 180 pounds to 165 pounds (82 to 74 kg) over
the course of the 1996 season. Injuries to teammates and large numbers of
penalty killing situations gave the Sharks' captain more than his share of ice
time. Sharks Strength and Conditioning Coach Steve Millard told us that the team
monitors the players weight and that, "Fifteen pounds is more significant than
we like to see." They gave Gill nutritional supplements to help him keep his
body weight up. Millard told us that it was typical for a player to lose 6 or 7
pounds (3 kg) in fat and lean body mass during the course of the season. So why
is weight loss a concern? Apparently, losing that much weight indicates that a
player is constantly having his system broken down and he is not recovering. In
this situation, he is losing muscle mass and may be more susceptible to injury.
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