What biomechanics principles must be applied to best perform a goal shot in netball?
These principles include;
- Base of support/centre of gravity, line of gravity
- Push-like movement pattern/kinetic chain
- Angle of trajectory
- Force/inertia/momentum
These principles are all in conjunction with each other and result in a more efficient and effective netball game.
The Answer
How can the base of support increase balance?
A game of netball involves both static and dynamic balancing. The specific skill of netball goal shooting begins with the successful management of static balance. Static balance differs from dynamic balance, which involves controlling the balance of the body whilst it is in motion. Static balance is described by The United States Tennis Association as “The ability to control the body while the body is stationary.” The amount of balance that a person has is linked to their body’s base of support. The base of support will change depending on the activity being done – for example, in gymnastics a competitor’s base of support would be their hands when they are doing a cartwheel or handstand. This particular moment of shooting a goal in the netball game is primarily the base of support being the feet planted on the ground.
A shooter standing with their two feet placed on the ground, shoulder width apart increases the core stability of the player and keeps the centre of mass above the base of support - giving optimum stability. Figure 1 shows a person’s centre of gravity directly over their feet (base of support). The central person in the picture shows the line of gravity falling directly over the centre of gravity. This demonstrates the most stable way in which a player can stand when considering the forces relative to netball.
Figure 1. Centre of Gravity
On occasion, players may also reduce the stability of their base of support in order to give them closer positioning to the ring. This can be seen when a shooter lifts one leg off the ground and leans in towards the ring. The biomechanical principle encourages a larger base of support (both feet on the ground) however the game situation can often mean that players must compromise biomechanical principles in order to obtain a better end result.
Does the push-like or throw-like movement pattern provide a more beneficial outcome in a netball goal shot?
The action most commonly used to throw the netball into a goal ring is the push-like movement pattern. This is a movement that replicates the motion of pushing something and where all joints extend in conjunction with each other (Blazevich, 2010). The push-like movement often provides optimal outcomes in netball goal shooting because it allows the kinetic chain of the body to create a straight-line movement. This chain not only maximises the result of the forces being put into movement but also increases the accuracy by ensuring that all parts of the kinetic chain are aimed towards the goal.
The process can be thought of as;
- Stable base of support
- Slight bend in knees to build momentum
- Upwards motion using knees to project forward while pushing up on toes
- Extend shooting arm upwards
- Push ball off tips of fingers in an upwards movement
This sequence allows the energy to build up throughout all the joints being used in a way that maximises both force and accuracy.
Does the push-like or throw-like movement pattern provide a more beneficial outcome in a netball goal shot?
The action most commonly used to throw the netball into a goal ring is the push-like movement pattern. This is a movement that replicates the motion of pushing something and where all joints extend in conjunction with each other (Blazevich, 2010). The push-like movement often provides optimal outcomes in netball goal shooting because it allows the kinetic chain of the body to create a straight-line movement. This chain not only maximises the result of the forces being put into movement but also increases the accuracy by ensuring that all parts of the kinetic chain are aimed towards the goal.
The process can be thought of as;
- Stable base of support
- Slight bend in knees to build momentum
- Upwards motion using knees to project forward while pushing up on toes
- Extend shooting arm upwards
- Push ball off tips of fingers in an upwards movement
This sequence allows the energy to build up throughout all the joints being used in a way that maximises both force and accuracy.
Despite the beneficial elements of this approach, one major downfall of the push-like pattern is the slow movement speed (Blazevich, 2010). This slow speed may provide the opposing team with a chance to intercept the ball while it is in flight. The throw-like pattern provides more force and speed behind the object (the netball) but follows a curved pattern and therefore reduces the accuracy of the shot. As with all biomechanical principles, there is a compromise between accuracy and speed. The accuracy is paramount to scoring a goal – which is the main desire of the game of netball. Other factors can be taken into consideration to increase the chance of scoring a goal, even with the reduced ball speed.
How can the angle of trajectory provide better goal scoring results?
When an object is projected through the air at an angle, it is called projectile motion. A netball in projectile motion can be influenced by the angle that the ball is thrown at, the speed at which it is thrown and also the distance between the thrower’s release point and the height in which it must reach eg. the netball ring (Blazevich, 2010).
As previously discussed, the speed of the ball release is slower because a netball goal shooter most commonly uses the push-like movement pattern. Due to this, the angle of projection must be measured with the force behind the ball in order to accurately shoot a goal. Blazevich (2010) notes that “At a projection angle of 45 degrees, the object will have an equal of vertical and horizontal velocity and its range will be maximised.” This relates back to the principle of gravity, which pulls an object back down to earth. For this reason, a netball shooter must take gravity into account and project the ball at an angle that allows it to travel horizontally towards the ring but also vertically upwards. By aiming high, this allows gravity to pull the ball back down into the ring rather than when the throw is more horizontal where the ball has a greater chance of rebounding off the ring rather than falling straight through the net.
How can force be applied with the optimal result?
Force is listed by Blazevich (2010) as being “The product of mass and acceleration; induces a change in the mobile state of an object.” When a player is in a state of static balance with the netball in hand, force must be exerted in order to change the inertia of the ball – the state of rest. Blazevich (2010) states Newton’s second law as being that, “The acceleration of an object is proportional to the net force acting on it and inversely proportional to the mass of the object.” Newton’s second law would say that the greater the mass of a netball, the more force that must act upon it. The force that must be applied to the netball when shooting for a goal is dependent on the distance in which the ball must travel. More force will move the ball further; though the angle of trajectory is just as important when calculating the release. The previously discussed push-like movement patters is a key component of controlling the direction of the force being applied during a netball goal shot. Someone who is standing on the edge of the goal circle will need to apply more force horizontally than someone who is right under the goal ring, but someone who is shooting from directly under the ring will need to apply more of an angle to increase the vertical travel of the ball. The arm length of each player is also a consideration when some can get the ball closer to the ring whilst still maintaining the ball in their shooting hand. Having one hand pushing the ball and the other hand as the guide also maximises the force of the motion whilst maintaining accuracy.
How else can we apply it?
The base of support is relevant to every sport; however each sport has different considerations based on game tactics and situations. For example, a basketball player is going to encounter opposition from the defending team so their base of support is often changing to accommodate the direction from which the other team is attacking from. Basketball players also need to use dynamic balance because the rules of the game allow for more motion and travelling. In the same way, a judo competitor would be constantly adjusting their balance in order to best his or her opponent but a basketball free-throw would use the same static balance as within the netball goal shooting context.
Figure 2 shows an example of the Stork Balance Stand Test. This test can be used to increase the balance and awareness of those within a variety of sports. The results found from these tests can be used as a key coaching and teaching point to give players feedback on their current levels. There may also be a consideration to the mass of the ball in the hands of a player. If greater mass provides greater stability, then hand size may even play a role in the balance of the ball in the hand whilst attempting the goal shot. For this reason that beginning sports players use modified equipment so that the mass of the equipment and player is more proportionate than using full-sized equipment.
Figure 2: The Stork Balance Stand Test
One individual factor relating to netball is the rules that prevent opposition from stepping within 3 feet of a player and also prevent them from making physical contact (Teach PE, 2013). Netball rules also dictate that a player can hold the ball for a maximum of 3 seconds so quick thinking is necessary to balance and then to also summate their forces. When looking at goal shooting in game context, it is visible that although an opposing player cannot physically change the position of the goal shooter, the shooter must still consider quickly and carefully the best way to place their body for balance when attempting to score a goal.
After investigating these biomechanics principles in the context of netball shooting, it can be said that the quality of game can be greatly increased by taking these factors into consideration. The study and teaching of these principles to beginners and elite players alike can provide a fantastic understanding and approach to netball and goal shooting in particular. The optimal performance in the shooting position is a vital strength of any team and it is therefore important to acknowledge the biomechanics behind successful technique and tactics.
References
Blazevich, A. J. (2010). Sports Biomechanics. London: Bloomsbury.
Teach PE. (2013). Netball Coaching. Retrieved from Teach PE: http://www.teachpe.com/netball/rules.php
United States Tennis Association. (2013). Sport Science. Retrieved from United States Tennis Association: http://www.usta.com/Improve-Your-Game/Sport-Science/114378_Technique_Basic_Terms_and_Principles_in_Biomechanics/
Sharkey, B. G. (2006). Sports Physiology for
Coaches. Champagne: Human Kinetics.
