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# Biomechanics of a Hockey Shot

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## Ben Shapiro

on 10 January 2014

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#### Transcript of Biomechanics of a Hockey Shot

Biomechanics of a Hockey Slapshot
Overview of Hockey
History of Hockey
5 Phases of
A Hockey Slapshot
1. Preliminary Movement
2. Backswing/Wind-Up
3. Force Producing Movement
4. Critical Instant
Expert Preliminary Movement
Expert Backswing/Wind-up
Expert Force Producing Movement
Expert Critical Instant
Novice Preliminary Movement
Novice Backswing/Wind-up
Novice Force Producing Movement
Novice Critical Instant
7 Principles of Biomechanics
Stability
Principle #1:
The lower the center of gravity, the larger the base of support, the closer the line of gravity to the center of the base of support, and the greater the mass, the more STABILITY increases.

Maximum Effort
Principle #2:
The production of maximum force requires the use of all the joints that can be used.

Principle #3:
The production of maximum velocity requires the use of joints in order – from the largest to the smallest.

Linear Motion
Principle #4:
The greater the applied impulse, the greater the increase in velocity.

Principle #5:
Movement usually occurs in the direction opposite that of the applied force.

Angular Motion
Principle #6:
Angular motion is produced by the application of force acting at some distance from an axis (or a torque).

Principle #7:
Angular momentum is constant when an athlete or object is free in the air.
Principle 2
Principle 3
Principle 4
Principle 5
Principle 6 & 7
Conclusion
Principle 1
Expert Hockey Shot
Novice Hockey Shot
In the preliminary movement of a slap shot, the expert stands with his skates, hips, and shoulders square to the puck. He has a relaxed grip on his stick and the puck is cradled within the curve of his stick to place it in the ideal position for a shot. This ideal position is about one and a half feet ahead of him and in line with his back foot. One of his hands is on the end of the stick while the other is a third of the way down. He is in a balanced, slightly forward stance with his centre of mass just in front of him. His stick is also on the ice to provide a full range of motion for the backswing.
In the preliminary movement for the novice's slapshot, he is positioned very differently. His feet are pointed outwards and slightly too narrow. His back is hunched over, causing his centre of mass to be too far forward and throwing off his balance. His bottom hand is over halfway down the stick which is too far. Since it is so far down, he will have to hunch over even more than he already is to reach the puck during his shot, thus sacrificing more balance. He is holding his stick at his waist instead of on the ice, causing the puck to be way too far ahead of him and not in his control.
When the expert executes his backswing, he widens his stance to improve his base of support and balance. He pushes the puck forward so that the it will be in the exact spot that he strikes the ice on his shot. He shifts his weight to his right leg and slightly draws his left leg backwards to get a better angle on the puck. His torso completely rotates so his shoulders are perpendicular to his hips for maximum rotational velocity. His arm slides down the shaft of the stick, closer to the middle, so he can achieve more power and control on the downswing. His left hand is completely across his body to allow the stick to be as far back as possible. This will provide a larger distance to build up speed on the downswing.
When the novice winds up, he doesn't change his foot position. Because of this, he can't generate power from his legs for the shot through weight transfer. Since his preliminary movement didn't start with his stick on the ice, the puck is stationary and the position can't be adjusted to a place where he can contact it easily. The puck is now too far in front of him and too far to his left to hit from a balanced position. His right arm is at his left hip which is restricting the distance the his stick can wind-up. The novices barely rotates his trunk which will cause a sever reduction in power and backswing distance. As shown by the yellow lines on the pictures, the novice's stick doesn't even reach 90 degrees whereas the expert's stick is almost at 180 degrees.
In the expert's force producing movement, he uncoils his trunk completely while shifting his weight to his front foot. This generates the maximum amount of power possible. To maintain control, he slides his hand down the shaft of the stick to shorten the distance between his body and the point of contact with the puck. The blade of his stick connects with the ice just before the puck to allow for the stick to flex for more power. He digs his left skate into the ice to establish a base and to prevent his body from drifting. He strikes the puck with his hip and shoulders pointing in the direction that he wants the puck to go.
Hockey is a sport in which players from two opposing teams, each composed of 5 players and a goalie, attempt to shoot a rubber puck into into a net on either side of an arena using "L" shaped wooden or composite sticks. It is played on an ice surface with each player wearing skates (boot with sharpened metal underneath). Each time one team puts the puck in the back of the other team's net, it is a goal. The team with the most goals at the end of the game wins. The game is split into 3 periods, each 20 minutes. If the score is tied after 3 periods, the game goes into a 5 minute overtime. In overtime the rule is "golden goal", which means which ever team scores first in the 5 minutes wins the game. If both teams fail to score, then the game goes into a shootout if not playoffs, and if it is a playoff game, into another overtime. In shootout, each team takes turns taking shots, one player at a time, at the opposing team's goalie, in 3 rounds.
The novice doesn't start with his trunk coiled so all the power from the force producing movement comes from his left tricep extending. since he is far away from the puck, he has to lean forward and down, destabilizing him and sacrificing power and balance. Just before he strikes the puck, he has built up virtually no angular momentum on the blade of his stick. His hips and shoulders are still pointed perpendicular to the direction that he wants the puck to go, causing an awkward motion when he shoots.
The expert strikes the ice just before the puck, in line with his front foot. His shoulders and hips are facing the direction that he wants the puck to go and his torso is completely uncoiled. His hands have moved up the shaft of the stick towards him to provide more of a sling-shot effect on the puck. His stance is wide and his whole body is stabilized. All of the power from his body is focused on the blade of the stick.
During the critical instant, the novice hasn't generated much power or balance. He is hunched over because of the puck's distance from him and his hand's position on the shaft. He has an equal amount of weight placed on both feet so he is not generating power from his legs. His feet are also narrow which causes an unstable base of support. He used only his left arm to swing the stick and hit the puck instead of his whole body (which the expert used).
The expert has his bottom arm outstretched and forming a straight line because during the shot, he utilized his joints from largest to smallest and his wrist was the last joint to act. His hips and shoulders are rotated slightly more to the left to dissipate the force of his previous uncoiling. His front foot is still planted and stationary, keeping his stability and his back foot is outstretched to ensure a base so he won't fall during the follow through. His eyes and the blade of his stick are pointed in the direction that the puck went in order to transfer all of the force in that direction.
The novice is still facing perpendicular to the direction that the puck traveled. Because of this, the force that he used to swing the stick is being transferred in front of him and causing him to fall forward. He also has his trunk completely flexed, moving his centre of mass far in front of him and throwing off his balance. His feet have still not moved from their original position so it is evident that no weight transfer has occurred. His shoulders form a vertical line with the ice, making it very likely that he will fall and is a hard position to recover from.
As we can see with the expert, his stance is a lot lower than the novice. He bends his knees and makes sure he doesn't lean too far forward or backwards so that he keeps his center of gravity close to his center of the base of support. The novice, however, keeps his legs fairly straight, and even leans a bit forward, causing his center of gravity to shift forwards. Thus, the expert has much greater stability. As we can see in the video, the expert remains stable the entire time, while the novice almost falls forward after performing his slap shot.
With the novice, we see he uses his joints correctly, from largest to smallest, in the preliminary movement. However for the actual slap shot, he first swings with his arms and then his core follows, which does not produce maximum force in the shot. The expert on the other hand, makes sure to first lead the shot with his core. Once his core has reached a half way point, he then swings his arms downward. His core then twists to face where he wants the puck to travel, and his arms follow suit.
In order for maximum force to be applied in the slapshot, the athlete needs to undergo a large range of motion. Although the novice underwent a similar range of motion with his arms, momentum wasn't 'carried through' the exercise and because of his minimal arm strength, the shot wasn't effective. Additionally the legs and core went through a larger range of motion and worked in conjunction with the arms to help the expert produce maximal impulse. Without incorporating any range of motion with the core/legs, the novice relied solely on force produced by the arms.
The hockey stick almost acts as an extension of the arm. The length of the stick adds to the distance of the axis - the point where the sweet spot of the hockey stick meets the puck - from the force producing muscles of the body, thus generating torque. The torque produced by the rotation of the whole body, individual body segments and the puck itself will be explored:

1. The expert rotates his whole body, there is rotation of the feet, legs, core and shoulders about the longitudinal axis, whereas the novice's body seems to bend forward at the hip along the horizontal axis as opposed to the other axes.

2. Both the novice and expert undergo a considerable range of motion in the arms but the novice relies solely on that relatively minimal force production because he doesn't recruit the larger leg or core muscles.

3. The projectile, in this case the puck, always goes in a parabolic pathway, but there are more efficient ways to make it go faster. Backspin or topspin would be incredibly detrimental when trying to perform a slapshot as this would increase the nutation or 'wobbling' of the puck in the air, thus increasing air turbulence and friction against it and ultimately slowing it down.
Streamlining the puck, where the side of the puck slices through the air and not the top/bottom, minimizes surface area, air friction, turbulence and maximizes angular velocity. Successfully streamlining the puck in layman's terms is called shooting a 'saucer', and is dependent on the conversion of force at the critical instant from the hockey stick sweet spot to the puck and the follow through, both of which the expert accomplished.

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A slap shot causes the puck to head in the direction the stick strikes it. During a game situation, where the puck comes from a pass called a 'one-timer', the athlete can, with careful timing, redirect the puck in the opposite direction by exerting a greater force on it. The resistance of the puck against the hockey stick exemplifies the movement occurring in the opposite direction of the applied force.
For maximum production of force, all the joints that can possibly be used for a movement must be used. For example, the expert is able to create maximum force because he bends his knees, then uses his hips, and after that his shoulders and even elbows. With all of these joints working together he is able to produce the desired force from the slap shot. The novice, however, only uses his shoulders, and basically relies all on arm strength to produce a shot. We can see however that the expert produces much more force by engaging all possible joints.
Principle 6 & 7 (Angular Displacement/Angular Velocity
When comparing angular velocity and angular displacement of the elbow joint, there are significant differences between the expert and novice. The five reference points were the preliminary movement, back-swing, force producing motion, critical instant and follow through

Angular Displacement
Although both athletes undergo a similar motion, the expert does it in less time and consequently performs it faster. The expert also experiences goes through a more sudden increase from the force producing motion to the critical instant and follows through effectively. The novice on the other hand goes from the force producing motion to the critical instant in a significantly longer time and instead of following though, cuts off the velocity of his motion drastically.

Angular Velocity
The difference between the techniques is shown much better in the angular velocity graph, because although both go through similar motions, the speed at which they're doing it is very different. The spike in the expert's angular velocity to almost 600 degrees/second versus the novice's pitiful 180 degrees/second critical instant speed indicates a successive transfer of force into the puck. In order for the novice to improve he must work on transferring maximal force at the critical instant and following through.

sweet spot
After considerable analysis of the 5 phases and 7 principles of biomechanics of slapshot technique by a novice and expert, numerous differences serve to explain what makes the expert more proficient. Recruiting larger muscles, effectively producing a larger amount of force, transferring that through the puck, following through with a fluid motion, and having a strong, wide base were some of the major differences between the two athletes. The expert was stabilized and balanced throughout his whole motion whereas the novice was constantly off balance. Through practice of the right techniques and increased strength by not skipping leg day, the novice can fix the errors in his form and make it into the NHL.
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