Biomechanics integrates the biological and mechanical principles of an activity for the purpose of improving human movement (Knudson, 2007 p 3). Understanding the biomechanical concepts of a skill is essential to improving the overall performance of that specific skill.
To propel a netball down a court using a system of throws from one player to another appears to be a simple process requiring speed, accuracy and distance. However, in reality it is far from simple. The effectiveness of a player’s ability to successfully pass the ball is essential for the success of the team as a whole.
The purpose of this blog is to examine the biomechanical principles behind several different passes including the chest pass, the single arm shoulder pass, the double handed over head lob throw and the bounce pass, all passes used within a game of netball.
The Chest Pass
In order to successfully execute a chest pass in netball all of the joints in our kinetic chain are required to simultaneously move in a single push-like movement pattern (Blazevich, 2007 p 196). The cumulated forces (or torques) generated from each joint results in a high overall force and a straight-line movement at the end point in the chain (in this case the hands) which makes the movement highly accurate.
Although the chest pass allows the ball to move at a higher force and more accurately, the push-like pattern of the pass has a slow movement speed, thus the speed of the pass movement is restricted by the shortening of our muscles (Blaxevich, 2007 p 197-198). However, stepping forward as the pass is initiated contributes to forward velocity and increases the momentum in the upper body and arms (Blazevich, 2007 p 202).
The use of two hands moving in a symmetrical forward direction provides the accuracy of the throw, and having the fingers spread helps to steer the direction of the chest pass (Russo & Izzo, 2011 p 43). This is why chest passes are generally used to cover small distances (relatively small forces are required). A chest pass is very efficient and one of the most commonly used movements in a netball game.
Image from: Blazevich, 2007 p 202.
Figure 1 shows the push-like pattern of the chest pass and how the symmetrical movement of the throw provides high levels of accuracy.
The Over Arm Shoulder Pass
A single arm shoulder pass requires the joints in the kinetic chain to extend sequentially (one after the other), unlike the simultaneous movement in the push-like movement of the chest pass (Blazevich, 2007 p 198).
An over arm throw movement begins in what is called the wind-up phase. During this phase the shoulder begins to extend (before the elbow and the wrist) and whilst the elbow is flexing by being drawn backwards. As the sequence continues there is a significant increase in the extension velocity of the hand and fingers, which results in a high ball release velocity. This flick movement of the wrist and fingers at the end of the over arm throw contributes to the speed at which the ball is released. During each of these sequential movements more momentum is generated and transferred through the production of large muscle forces. When a ball is thrown in this way it is given what is called ‘angular momentum’.
The efficiency of the throw-like pattern for gaining distance is the result of using tissues that have the fastest shortening speeds, the tendons. A tendon has high kinetic energy and stores elastic potential energy, so when it is released it recoils very quickly (at high speed).
This is why the over arm throw is used to pass the netball over larger distances. Although the larger distance causes the throw to be less accurate due to the hand and ball (end points of the chain) following a curved direction, the high speed and power generated through the ball allows the pass to be very effective for a longer distance throw. Flattening the arc of the throw by rotating the hips improves the over all accuracy of the throw (Hede et al. 2011 p 95).
Images from: Blazevich, 2007 p 198 & 203
As shown in figures 2 and 3, the over arm throw occurs in a sequential pattern. The movement begins with shoulder and hip rotation before moving to elbow acceleration, wrist acceleration and lastly a finger and ball acceleration.
The Double Handed Over Head Lob Pass
The double-handed lob pass or overhead throw is one of the least commonly used passes within a netball context. This throw requires the arms to be lifted and extended to where the back is slightly arched and the elbows are bent allowing the ball to be placed just behind the head. An appropriate amount of force is then applied to offload through the tension in the back and arms, and concludes with a fast outward movement that comes from the thumbs and fingers to propel the ball forward to its destination (Russo & Isso, 2011 p 44). The force used to propel the pass will be greater, more direct and more accurate, if the player steps forward as they throw because the wider base of the stance increases the stability of the player as they throw, and there will be some forward velocity and an increased momentum in the upper body and arms.
Whilst this pass still makes use of both hands in producing a relatively straight forward directed throw, elevating the arms to head height or above means that at the end point of the kinematic chain (the hand and ball) this pass may follow a slightly curved arc of motion and therefore be less accurate than a chest pass (Blazevich, 2007 p 203). Although, raising the arms will elevate the height of the pass with the possible advantage of clearing an opponent.
Figure 4 shows the extension of the arms over the head in preparation for an overhead lob throw.
The Bounce Pass
The bounce pass in netball is also one that is less commonly used. The bounce pass requires the flexion and extension of the arms and elbows similar to the double handed lob throw. By understanding Newton’s Third Law of Motion, the biomechanics of the bounce pass may be better understood. Newton’s Third Law states that “for every action there is an equal and opposite reaction” (Atherton & Young, 2009 p 273). A player exerts an action force onto the ball in a downward direction at which time the ball exerts a reaction force in an upright direction felt by a very slight increase in pressure on the fingers of the player. The ball travels downward before making contact with the court. The court exerts an upward reaction force back onto the netball causing it to bounce up and into the hands of the player receiving it.
Figure 5 demonstrates Newtons Third Law of Motion being executed through the biomechanical movements of the bounce pass.
So how can understanding the biomechanical principles and skill progression behind several different passes in netball allow a player to improve their effectiveness within a game?
A netballer must be aware of the desired outcome from the pass and select the pass that best suits the intended use. For example, how far does the ball need to travel to achieve the result, where are the players in the team in relation to the players from the opposing team and how are they obstructing the movement of the ball? A player must also take into account the rules of the game, as these will provide certain limitations in selecting the appropriate pass, for example the ball cannot be thrown longer than a third of the length of the netball court (Hetherington et al, 2009 p 1). All these considerations will affect the choice of the pass. Through understanding each type of pass a player is therefore able to determine whether a chest pass, a one-handed shoulder pass, a two-handed lob pass or a bounce pass is the best option to achieve the desired result within play.
It would appear that a chest pass is best used for accuracy and power over a short distance. Short powerful passes reduce the risk of interception from the opposing team’s players but still propel the ball down the court toward the goal circle. A one-handed shoulder pass is more effective when needing to cover longer distances or bypass areas of congested play to find a free player, but is less accurate and more likely to be intercepted. A two-handed lob pass is used to pass the ball with force and accuracy over shorter distances but at a higher directed height to try and clear an opponent. It is often used in and around the goal circle. A bounce pass is used to manoeuvre the ball around a defending player. If the opposition presents an obstruction to the movement of the ball towards the goal then a bounce pass around the defending player, or an overhead pass to surprise the opponent and clear their reach, may both be appropriate options.
Stepping forward in combination with each of these throws provides greater momentum and forward velocity to the pass due to the greater power and forward movement of the body (Atherton & Young, 2009 p 202).
There are however other biomechanical factors which could determine the result of each of these different passes. For example, the speed and angle at which a ball travels through the air may be influenced by gravity’s effect on the ball as it travels through longer distances, and the rotation of the player’s hips will alter the ball’s trajectory (Blazevich, 2007 p 204). It is also evident that further research into this area is required to gain a greater understanding of these principles and how they can be integrated within a sport such as netball; the use of video recordings is a great way to collect this type of data.
How else can we use this information?
Having a thorough understanding of these biomechanical principles not only allows a better understanding of how to improve results within a netball game context but the principles of each of these passes can be used in numerous other sports.
The push like movement pattern of a chest pass can be applied to other sports requiring a high degree of accuracy and force generation. Dart throwers make effective use of this pattern where the open kinetic chain nature of the movement allows the dart to be released with force over a relatively short distance, and with a deal of accuracy at the end point, as the dart continues in a straight line. It also has application in rugby, particularly in the scrum (Blazevich, 2007 p 197). Each upper limb joint generates a force and the accumulation of these forces produces a strong end force suitable for moving heavy objects such as the opposition players in the rugby scrum.
The biomechanics behind an over arm shoulder pass can be applied to javelin throwing where the aim is to cover as much distance as possible. Javelin throwers require large amounts of force and power to be able to effectively throw the javelin. This sport also incorporates a forward movement in the run up phase and rotation of the body to gain further distance.
The two-handed overhead lob throw is demonstrated within the game context of soccer during the soccer throw-in from the sideline. The player with the penalty must throw the ball over the heads of the opposition to land on the ground at the feet of a teammate, thus accuracy, power and executing this skill correctly is essential for maintaining possession within the game.
The bounce pass used in netball is very similar to the bounce passes which are sometimes used within the game context of basketball. A bounce pass may be effectively used to manoeuvre the ball around an opposing player at a lower ground level.
Today, netball is one of the most popular team sports within the Commonwealth. Understanding the biomechanical concepts of this sport allows players and coaches to improve their performance and skills. Although this blog has only focused on four of the most commonly used passes in the game there are so many skills needed in the game which could be improved by examining biomechanical principals, such as how to improve the accuracy and effectiveness of goal shooting, footwork and landings both in the goal circle and in general court play, or how to dodge around a player to receive a pass, as each type of pass that is thrown will affect the way in which the pass is caught (Steele, 1993 p 4). This information could not only improve a player’s skill but also teach them how to protect their body from injury by performing the skill correctly. Interestingly for example, Julie R. Steele suggests that changing passing techniques could minimise the potential risk for lower limb injury, in particular throwing higher passes such as the lob rather than hard and fast balls such as the one arm shoulder pass. It may be safer but is it as effective within a game context? (Steele, 1993 p 7).