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Introduction

The water polo shot is a unique skill in which the player attempts to score a goal by throwing the ball as fast and accurately as possible at the goalie. The throw is an overhand throw, similar to that used by a skilled baseball pitcher. Since the player is in the water, the skill is more difficult as they have no firm surface from which to push off. The skill is also difficult because the rules allow only one hand on the ball, so the ball must be controlled with only one hand throughout the shot. The ball is about twice as large as the average male’s hand, so it is difficult to control. It is even more difficult for the average female to control the large ball with one hand and the ball has to be balanced on the hand during the preparation for the throw.

The shot has some similarities to the overhand throw in baseball and softball. The following description applies to the right handed thrower. The ball is brought back behind the head and the trunk is rotated away from the direction of motion so the left shoulder faces the direction of motion of the throw. The throw is initiated by trunk rotation forward in the direction of the throw. In baseball, the hips begin the rotation and this is followed by the mid trunk, then the shoulder girdle, as the trunk acts as a 3 segment model. The throwing arm is abducted 90 degrees to the trunk and the trunk leans laterally away from the throw during delivery. The throwing arm then goes from shoulder lateral rotation and lower arm supination to shoulder medial rotation and lower arm pronation, usually accompanied by elbow extension and wrist flexion. The fingers remain extended during the throw in order to apply spin to the ball at release.

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Video 1: Above View of the Shot

The water polo shot differs from the baseball throw in several important respects, notably that the water polo shot is performed while the athlete is suspended in water and therefore lacks a firm base of support on which to push down and back. The legs and arms must therefore continue to perform sculling movements to help keep the trunk upright during the throw. The trunk often does not perform segmented rotation, but it usually rotates as a single unit. It is more desirable for the trunk to perform segmented rotation in which the hips move forward first and the shoulders follow (Ball 2005). The trunk rotation does provide an important source of power to the shot, as the trunk rotation helps to place the throwing arm in the optimal position to produce a powerful shot by maximizing lateral rotation. The trunk rotates forward and leaves the throwing arm and ball behind the body, producing a position of maximal lateral rotation. The angular momentum created by the trunk rotation is then transferred to the shoulder joint and to the throwing arm. The trunk rotation has been estimated to provide 30-35% of the contribution to ball speed (Ball 2005). The joint movements of the joints of the arm also contribute to the velocity of the hand, and the ball at release (Newland 2005).

There are two types of arm action seen in the water polo shot on goal, the more common overhand technique in which the ball is released from a high point above the head using primarily shoulder medial rotation for ball speed; and the sweep technique in which the ball is swept horizontally across the water surface using primarily horizontal adduction (Feltner and Taylor 1997). The technique described here is the overhand technique as it is more commonly used. It has been suggested that muscular strength is the main determinant for technique chosen in the penalty shot. Subjects who were stronger were found to be able to create the necessary muscle strength to use the overhand technique (Feltner and Taylor 1997).

Description of the skill

Preparation and Backswing

The shot starts with the player facing the goal with the ball in the shooting hand. Prior to the shot, the ball must be lifted upwards from the water. The rotation lift is a lift in which the hand is placed on top of the ball and a downward pressure is applied as the hand is rotated under the ball (Armour and Elliott 1989). This lift was found to produce a higher ball velocity in a group of elite players compared to the lift from underneath in which the hand is placed under the ball and the ball is raised directly from the water.

Figure 1. Hand on top of ball for rotation lift in preparation for shot

Figure 2. Underwater view of preparation for shot with hips and knees flexed and trunk turned sideways.

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Video 2: Underwater View of the Shot

The shooting arm is then raised above the shoulder (shoulder abduction) while the trunk is rotated away from the goal. At the furthest rear point of the backswing the shoulders should be almost in line with the target (Armour and Elliott 1989). This rotation places the trunk in position to apply the full forces of trunk rotation to the ball during the throw. The non throwing arm is abducted in front of the front shoulder and points in the direction of the throw. The throw is often initiated by the rotation of the front arm in the direction away from the throw to pull the front shoulder around and initiate trunk rotation. The front arm is horizontally abducted and extended to start the trunk rotation.

Figure 3. Ready position for the shot- hand on top of ball.

Figure 4. Top of backswing for the shot, ball over shoulder and chest out of the water.

The height of the trunk out of the water during the throw is a critical factor in shooting technique (Newland 2005). Players should be able to raise their bodies out of the water a sufficient distance (.2m above start height) to allow the best use of trunk rotation and upper limb action in the throw (Armour and Elliott 1989). Since the resistance of water to movement is greater than that of air, the more movements that occur out of the water the faster the shot should be. As well, the higher the shot at release the less chance that the shot will be blocked by a defender (Feltner and Taylor 1997).

At the top of the backswing the throwing shoulder is first medially rotated, then laterally rotated prior to the forward movement of the ball and hand. The amount of medial rotation at the top of the backswing is dependent on the size of the hand and the ability of the player to control the ball in one hand. Few female players are able to hold the ball in one hand with the ball facing the water- usually the hand is under the ball to support it. At the furthest point of the backswing the mean elbow angle was 107º for elite male players while the ball was held on average 19 cm above and 33 cm behind the ear. The top female athletes in a sample of elite Australian players recorded similar angles and distances to the males (Armour and Elliott 1989). Wrist hyperextension is a key feature of the arm position during the backswing, and was found to average 70º from the anatomical position (Armour and Elliott 1989).

The legs also have an important role in force production in the overhand throw, as they are forcefully extended during the throw. The eggbeater kick increases in speed during the preparation for the throw, and helps to raise the body for the throw. Hips, knees and trunk are flexed maximally just before the shot, then are forcefully extended to raise the upper body out of the water for the shot- called the boost. This forceful extension of the hips and knees, especially the left hip and knee, also provides the necessary reaction force required to take up the rotation of the trunk and throwing arm. Skilled throwers exhibit very forceful extension movements of the legs, primarily the front leg which is flexed at the hip and extended at the knee to take up trunk rotation while the trunk is rotating forward.

Figure 5. Trunk rotation prior to release in the throw. Left leg is used to take up the rotation of the upper body by extending and abducting.

Forward Swing to Release

The technique of the water polo shot on goal is similar to that seen in a skilled baseball pitcher. The larger muscles of the trunk act first, producing trunk rotation in the direction of the throw as well as trunk flexion forward during the throw. The trunk starts the throw in a position of hyperextension and moves into 20 degrees of flexion during the throw. This trunk motion can also assist in producing ball velocity during the throw. The most important muscles in the trunk are the anterior trunk muscles that pull the right side of the trunk around to face the target (Newland 2005), as well these muscles are active in flexing the trunk forward. Trunk strength is a critical aspect of the water polo shot, as the contribution of the trunk to the speed of the shot is up to 30-35% of ball speed (Ball 2005). As the player rotates the trunk (shoulder girdle) forward to face the goal, the ball and the throwing arm are left behind. It has been reported that female water polo players use very little hip and shoulder rotation compared to the male players, and are often facing forward already at the end of the backswing (Elliott and Armour 1988).

The shoulder moves into lateral rotation, the elbow is flexed (Armour and Elliott 1989) and the ball is resting on the palm of the hand. This action of leaving the ball behind the body is critical in producing maximal force on the ball, as the anterior shoulder muscles and the triceps are placed on a stretch prior to forceful contraction during the throw. The throwing shoulder should maintain an angle of 90 degrees of abduction during the throw, to prevent impingement that may occur if the arm is abducted to an angle greater than 90 degrees. It has been reported that the predominant injuries seen in water polo athletes are subacromial impingement and rotator cuff tendonitis resulting from combined adduction, horizontal adduction and medial rotation of the throwing arm (Rollins, Puffer et al. 1985; Whiting, Puffer et al. 1985). Hyperabduction is the main factor in producing subacromial impingement, as the supraspinatus tendon is pinched under the acromion and tendinitis often results. Players should attempt to keep the abduction angle close to 90 degrees to prevent these type of shoulder injuries. Increased height of release of the ball is gained by lateral trunk flexion to the left, away from the throwing arm, which allows the abduction angle to remain close to 90 degrees as well as increasing the moment arm for spinal rotation.

Figure 6. Arm position at top of backswing, trunk rotated sideways.

Figure 7. Arm position at release, trunk facing forward

As forward trunk rotation is nearing completion the arm action begins, so the movements occur in a sequence from larger to smaller joints. The shoulder is medially rotated and horizontally adducted by the anterior shoulder muscles, the elbow is moved toward extension and the lower arm pronates to apply additional force and spin to the ball. The range of motion of medial rotation during the throw has been reported to range from 40 to 80 degrees, with velocities approaching 500 deg/s (Ball 2005). These values are quite high, but are not comparable to those attained by skilled baseball pitchers whose peak medial rotation velocities approach 7000 deg/s (Feltner and Dapena 1986). The horizontal adduction of the upper arm during the throw ranges from 50 to 80 degrees, with angular velocities approaching 80 deg/s. It has been estimated that medial rotation and horizontal adduction contribute 20-30% to developing ball speed (Ball 2005).

Figure 8. Front leg position at backswing- hip flexed 60 º and knee flexed 60 degrees.

Figure 9. Front leg position at release- hip flexed 20º and knee extended 150º

The elbow is flexed from 80-90 degrees during the forward swing as maximal lateral rotation is reached at the top of the backswing, and then goes through a range of extension prior to release. It has been suggested that elbow extension contributes 22-27% to development of ball speed at release (Ball 2005). The elbow does not completely extend at release, but the elbow angle at release is close to 150º for male throwers and 125º for female throwers (Armour and Elliott 1989). This partial flexion may be to prevent elbow injuries produced from high extension velocities near the end of the range of motion. It has also been reported that a group of injured water polo players (shoulder impingement) had less elbow flexion than a group of noninjured players (Whiting, Puffer et al. 1985). As well, increased elbow angles at release increase the moment arm for medial rotation during release by increasing the distance from the axis through the upper arm to the ball (Feltner and Taylor 1997).

Figure 10. Elbow position at release, elbow close to 155º, not at full extension.

Figure 11. Shoulder position at release, shoulder close to 90 º to the trunk to avoid impingement. Trunk leans 30º away from vertical position.

This will significantly increase ball speed at release from shoulder medial rotation. The wrist also makes a contribution to ball velocity (8-13%) by flexing during the forward swing and at release. Although an early study (Davis and Blanksby 1977)reported that there was no change in wrist angle prior to release, more recent studies have suggested that wrist flexion is an important aspect of force production in the throw. Male throwers were seen to experience some increased wrist extension during the forward arm swing, followed by wrist flexion at release. This increased wrist extension increased the range of motion for wrist flexion and increased the contribution of the wrist to ball velocity. The wrist angle was close to 155º at release, and the forearm is almost vertical (Armour and Elliott 1989).

Figure 12. Maximal lateral rotation of the shoulder occurs as the trunk rotates forward for the shot and leaves the hand and ball behind- places medial rotators on a stretch.

The non-throwing arm may assist with support while the trunk is rotating backward by performing sculling motions. These motions may assist with body support while the trunk is raised out of the water for the shot. The front arm may also assist with trunk rotation by horizontally abducting and extending during the throw. This movement may produce more forceful trunk rotation and also assist with lateral flexion.

Trunk lean is also an important aspect of the shot, as the arm actions are occurring the trunk leans to the left, away from the throwing arm. This position will increase the lever arm for rotation of the arm around the axis through the spine, and increase the velocity of the ball around that axis. Most skilled throwers will lean at least 30 degrees away from the throwing arm at release. This position will maximize the lever arm for trunk rotation as well as increase the height of release of the ball. A higher height of release will allow a flatter angle of release and greater horizontal velocity of the ball towards the goal. Skilled throwers were found to have greater angles of lateral trunk lean than unskilled players, and females were found to have more vertical trunk positions than males (Armour and Elliott 1989). The speed of lateral trunk movement was found to be related to the velocity of the ball at release. A study (Ball 2005) of a faster and a slower throwing group of elite water polo players revealed that the faster throwers had a significantly greater lateral trunk speed at release. The faster throwers had a trunk lateral flexion velocity of .77 m/s at release, while the slower throwers had a lateral trunk velocity of .406 m/s.

Figure 13. Wrist flexion during release helps increase the speed of the ball as well as impart backspin to the ball to stabilize flight.

Follow Through

Following ball release the elbow continues to extend, the shoulder flexes, the forearm continues to pronate and the wrist continues to flex to ensure that peak ball velocity was achieved at release. The body segments should slow down gradually over the greatest time and distance possible to prevent overuse injuries to the throwing arm. These injuries could include rotator cuff strains, impingement syndromes and elbow muscle strains.

Figure 14. Wrist flexion should be present in the follow through, as well as lateral trunk lean away from the ball.

The ball will leave the index and middle fingers last, allowing the backspin to be applied to the ball. Some throwers have the ball leaving both the 2nd and 3rd fingers last (Armour and Elliott 1989). The throwing arm will decelerate over a long follow through forward and to the left to prevent injuries to the throwing arm by decreasing the speed over the greatest time and distance possible.

 

Speed of the Shot

The speed of a fast shot in water polo for highly skilled players can reach up to 22 m/s, which is close to 80 km/h or 50 mph (Ball 2005). The forward swing time for the ball from first forward movement to release was found to be .17 sec for the faster throwers and .16 for the slower throwers (Ball 2005). The angle of release for most shots was found to be close to 4º for both males and females. The speed of the ball at release is dependent on the strength and technique of the thrower, as well as on the length of his arms and amount of lateral trunk lean. A faster shot has a greater likelihood of scoring because the goalie has less time to react to the ball.

Figure 19. Stromotion sequence of arm positions during release of the ball. Note ball is released at peak height of forward excursion.

Figure 20. Stromotion sequence of the ball from release to scoring a goal in the right corner of the net.

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Video 3 & 4: Shooting to Beat the Goalie

Other Factors in Shooting on Goal

Water polo players usually have a defender between themselves and the goal, so they have to shoot around or through the arms of a defender. This action will alter the mechanics of the shot, and may not allow the player to use all of the joints through an optimal range of motion for every shot. Many shots feature a very quick release or one with a shortened backswing and decreased trunk rotation. Players often use the sweep shot which is a horizontal arm movement consisting of horizontal adduction that allows the shooter to shoot around the defender.

The player must also attempt to deceive both the goalie and the defender when taking the shot. This often forces the player to use head fakes or ball fakes to get the defenders moving in the wrong direction prior to the actual shot on goal. The player shooting on goal will often try to be deceptive by looking at one side of the goal and then shooting at the other side. The player may also point the shoulders in one direction, and then shoot to the other corner of the goal in order to be deceptive. Another deceptive move used in water polo is the delay shot, in which the shot is delayed in mid swing before accelerating into release to deceive opponents. Ball (2005) has reported that the delay shot is slower at release than the regular shot on goal, but the final arm movements prior to release are faster.

Variables to look at/measure when coaching the shot:

Range of trunk rotation at the end of the backswing- greater range of trunk rotation will produce a faster shot (at least 90 degrees) Height of the trunk out of the water during shot (20 cm is optimal) Height of the hand and ball above the head during the shot Amount of shoulder lateral rotation produced during the trunk rotation forward, prior to medial rotation at release Position of shoulder abduction during delivery- should be close to 90 degrees during shot; increased shoulder abduction angle can lead to shoulder impingement problems Amount of elbow flexion at release- should be close to 150º, or 40º short of full extension Lateral trunk lean during release of the ball- greater trunk lean will produce higher heights of release and lesser angles of shoulder abduction; increases the lever arm for shoulder rotation Angle of release of the ball should be close to the horizontal to maximize speed of ball Maintaining control of the ball during the forward swing- hand is kept under the ball and fingers grasp the ball Hips, knees and trunk are flexed maximally prior to the shot, then are forcefully extended to raise the upper body out of the water for the shot- the boost Not looking at the target point in the goal while shooting

Figure 21. This female athlete shows a good boost position out of the water during the shot; she could have greater trunk rotation backwards at this point in the shot.

References

• Armour, J. and B. Elliott (1989). "The overhead penalty throw in water polo." Sports Coach (January-march): 27-30.
• Ball, K. (2005) Biomechanical analysis of the water polo delay shot www.coachesinfo.com.
• Ball, K. (2005) Biomechanical analysis of the water polo fast shot www.coachesinfo.com.
• Ball, K. (2005) The Shot: Described www.coachesinfo.com/article.
• Davis, T. and B. A. Blanksby (1977). "A cinematographic analysis of the water polo shot." Journal of Sports Medicine 17: 5-15.
• Elliott, B. and J. Armour (1988). "The penalty throw in water polo: A cinematographic analysis." Journal of Sport Sciences 6: 103-114.
• Feltner, M. and J. Dapena (1986). "Dynamics of the shoulder and elbow joints of the throwing arm during a baseball pitch." International Journal of Sport Biomechanics 2: 235-259.
• Feltner, M. E. and G. Taylor (1997). "Three-dimensional kinetics of the shoulder, elbow and wrist during a penalty throw in water polo." Journal of Applied Biomechanics 13: 347-372.
• Newland, E. (2005) Good Outside Power Shooting www.users.bigpond.com/MSN/paulw01/shooting_knowledge.htm.
• Rollins, J., J. C. Puffer, et al. (1985). Water polo injuries to the upper extremity. Injuries to the throwing arm. B. Zarins, J. R. Andrews and W. G. Carson. Philadelphia, Saunders: 311-317.
• Whiting, W. C., J. C. Puffer, et al. (1985). "Three dimensional cinematographic analysis of water polo throwing in elite performers." American Journal of Sports Medicine 13(2): 95-97.