The Question
Biomechanics and its application sports is the science concerned with the internal and external forces acting on the human body and the effects produced by these forces. (Blazevich, 2010). Netball is both a popular form of recreational activity and a prevalent sport in Australia. It is important to consider and understand the biomechanical principles involved in performing a successful netball goal shot. This information can provide sporting personnel with a theoretical basis within which to teach the skill of netball goal shooting in order to optimise a player's technical performance. This post is directed at outlining the underpinning biomechanical principles involved in netball shooting such as; player's support/grounding (centre of gravity); the importance of force summation and the kinetic chain; and the trajectory motion/Magnus Effect.
Stability and Centre of Gravity - Preparation Phase
The centre of gravity refers to the point around which all the particles of the body are evenly distributed and therefore the point at which we could place a single weight vector is the body's centre of gravity (Blazevich, 2010). A solid grounding or base support is crucial when performing a netball shot in order to maximise potential balance and stability. This can translate into a more accurate skill execution. Excessive trunk movement during the skill execution can negatively impact on the stability of the athlete. With this in mind, the athlete benefits from performing minimal movement through their trunk and arms (Steele, 1993).
Figure 1.1 (Hede, Russell & Weatherby, 2011)
Figure 1.1 illustrates the body's centre of gravity shifting depending on movement and position. This shows that the larger the area of base support, the greater the stability.
Figure 1.1 suggests that a low centre of gravity, in regards to base support, can improve stability. Netball shooting differs from other sports in terms of biomechanical consideration. Shooters need to manage their static balance which differs from dynamic balance as the body is not in motion. The balance an athlete can achieve is linked to their base of support which, in the example of netball shooting, is the planted feet on the ground at a shoulder width distance apart with the trunk engaged. This keeps the centre of mass above the base of support which optimises stability. Skilled netballer shooters maintain a relatively upright trunk position and lean backwards slightly with their head upright and cantered in the midline of the body to achieve a balanced shooting stance (Steele, 1993). The described principles take place during the preparation phase of the skill sequence where the athlete is transitioning into the movement cues for the pre-release phase.
Force and Rapid Acceleration - Pre Release/Force Generation Phase
Newtown's Second Law states that "the acceleration of an object is proportional to the net force acting on it and inversely proportional the mass of the object" (Blazevich, 2010). Simply put, in order to change the motion of an object, a force needs to be applied. This principle relates to the force which is applied to the ball in order for it to travel towards to netball ring. In order to achieve maximum force during the execution phase, it is important to consider the combined forces of different body parts. This is called the summation of forces which is directly influenced by the number of body parts used in a movement, and the order and timing of their application (Blazevich, 2010). A goal shooter in the sport of netball uses the combined force generated through the legs, trunk, shoulders, arms and wrist throughout the different phases of delivery. This summation of force can be described as sequential from the legs, trunk, upper arm, forearm and the hand (Knusdon, 2007). This generation of force is made possible through the understanding of Newton's Third Law whereby "for every action, there is an equal and opposite reaction" (Blazevich, 2010).
Figure 1.2 (Beaumaris Netball Club, 2015)
Figure 1.2 displays the simultaneous flexion of the elbow and knees as described through the summation of forces. Force production is not necessarily just about producing the maximum force possible. In this example of netball shooting, accuracy is fundamental for successful skill execution. In Figure 1.2 we see a netballer in the shooting position, knees are slightly bent creating force on rigorous extension, trunk is in an upright position and elbows are bent ready for a soft extension with wrist extended backwards which increases hand motion. This summation of forces will allow for a greater release height and greater release velocity (Blazevich, 2010).
The Kinetic Chain - Execution Phase
The kinetic chain refers to a movement where all joints extend in conjunction with each other (Blazevich, 2010). In the example of netball shooting, this movement pattern provides optimal performance output as it allows the kinetic chain of the body to create a straight-line movement. This not only maximises the translation from force generation into execution but also increases the accuracy of the shot by ensuring all parts within the kinetic chain are directed towards to netball ring. This skill focuses on the push-like pattern within the principles of the kinetic chain. Again, this process utilises the athlete's stable base of support, the slight bend and upward propulsion of the knees, the extension of the elbow and final release point of the ball from the athlete's fingers. Inversely, a throw-like action would result in greater force generation yet would hinder the potential accuracy of the shot. As accuracy is the main determinant of successful execution, the push-like pattern is therefore the best design to utilise in netball shooting.
Trajectory Motion
The trajectory motion and angle of release are important principles to consider when performing a netball shot. Projectile motion refers to the motion of an object projected at an angle into the air (Blazevich, 2010). An example of how projectile motion can influence the outcome of a movement is that when a ball is thrown straight up into the air, it will stay in flight for a long period of time but only travel a small distance in terms of displacement, however, if a ball is thrown at an equal force but on a 45 degree angle of release, it will travel a further distance but stay airborne for a shorter amount of time. Therefore, we can see the importance of finding the optimal angle of trajectory through this combination. The factors that effect projectile motion include gravity and air resistance. This is influenced by Newton's Law of Gravitation, where the sum of forces dictates the acceleration of the object and the force of gravity acts downwards (Blazevich, 2010). The trajectory of a ball is influenced by projection speed, the projectile angle and the height. There is evidence to suggest that the optimal angle of trajectory is slightly above 45 degrees (Steele, 1993). The closer to the ring the shooter is, the greater the trajectory angle needs to be as the speed of the projected object will be determined by the height it reaches before gravity accelerates in back down towards earth (Blazevich, 2010).
Figure 1.3 (Advantage Basketball Camps, 2002)
Figure 1.3 displays the difference in the angle of release and how this can affect the projectile motion of the ball on its path to the ring. This example can be directly transferred into netball shooting as the hand technique and movement outcomes are parallel to that of basketball.
The ball release in an important aspect to consider when performing a goal shot in netball. To achieve optimal performance, the ball should be released when the arm is straight but not in a rigid manner. The higher the release of the ball is recognised as being beneficial as this creates a situation where the ball is being released from its highest possible point and therefore reducing the distance the ball must travel in order to reach the ring (Steele, 1993) and reducing the likelihood of it being intercepted by a defending player.
The Magnus Effect
The use of biomechanical principles can also be used through the technique in which the ball is released when shooting. Influencing the ball with spin is referred to as 'The Magnus Effect' and can attribute the success in performing a netball shot. This refers to changing the trajectory of an object towards the direction of spin which creates a Magnus force. An easy way to understand this principle is to imagine a spinning ball; as the ball spins it generates friction between the ball and air and causes the air particles to spin in the same fashion as the ball (Blazevich, 2010). When the ball impacts with the ring, the spinning momentum (which has resulted in an increased velocity) will increase the likelihood of the ball rebounding into the ring as opposed to bouncing straight out upon impact. In order to achieve maximum performance when shooting in netball, a small amount of backspin should be imparted onto the ball during the release phase and this can be achieved by flicking the wrist as the ball is released.
Figure 1.4 (Knusdon, 2007)
Figure 1.4 demonstrates the collision between the oncoming air and the ball (which is influenced with spin) and has resulted in a decreased velocity on one side of the ball. Under the principles of 'The Magnus Effect' the other side of the ball is able to pass through the air unobstructed and has resulted in an increased velocity towards the direction in which the spin was applied (Blazevich, 2010).
The Answer
In summary, we have learned that in order to successfully perform a netball goal shot a series of biomechanical principles must be considered and applied to optimise performance:
- The importance of the preparation phase is to ensure the athlete has achieved a strong base of support in which provides the grounding for the following movement cues. Ensuring the athlete creates a consistent and solid centre of gravity will increase their stability when attempting to execute the skill. This can be achieved by maintaining their foot positioning to be a shoulder width apart distance with knees bent in order to allow for a smooth transition into the next phase
- The summation of force during the pre-release phase provides the generation of force that is required to execute a netball shot. While achieving maximum force is not an objective within netball shooting, the sequence in which this force is generated is of great importance. This process addresses the simultaneous rigorous extension of the knees and the soft extension of the elbows right up to the release of the ball from the upwardly extended wrist.
- The application and understanding of the kinetic chain also supports the combination of forces from different body parts. The kinetic chain also allows maximum accuracy to be achieved through the extension of the different body parts in a straight-line direction towards the netball ring.
- The trajectory motion and angle in which the ball is released will greatly influence the direction and therefore accuracy of the shot. The ideal angle of release is slightly above 45 degrees and when combined with a high point of release (final stage of the kinetic chain), will again optimise performance.
-The theoretical understandings of The Magnus Effect provides the athlete with the greatest potential to score from a rebounding ball situation. Through the use of spin, the ball will generate an increase in velocity in one direction and decreased velocity in the other, allowing the ball to travel through the air with greater ease. By influencing the ball with a small amount of backspin upon release will allow the ball to rebound into the ring instead of bouncing directly out as would occur without the spin.
How else can we use this information?
This shooting technique is seen throughout many other sports and the mentioned biomechanical principles can be translated into other sports such as basketball and projectile sports. It is important to consider how a certain relationship and sequence between biomechanical principles may be optimal within one sport yet detrimental in others. For example, in the sport of javelin, the athlete's goal is to achieve the longest distance possible which utilises the previously mentioned projectile motion principles.
However, accuracy is of much less concern than in the sport of netball or basketball in which force must be forfeited to achieve maximum accuracy.
The main objective within netball shooting is accuracy. Our understandings of the biomechanical principles such as stability and support, summation of forces and the kinetic chain, projectile motion and the Magnus Effect allow us to transfer this knowledge into other areas. It is also important to acknowledge the relationship each of these principles share with one-another and how we can use this within future context. A sound understanding of these biomechanical principles will allow coaches and teachers to be able to successfully instruct players in a meaningful learning environment where they can learn to execute the skill to their optimum (Steele, 1993).
References
Advantage Basketball Camp. (2002). Advantage Basketball Camp's Shooting Camp. Available at: https://www.advantagebasketball.com/shootingcamp.htm
Beaumaris Netball Club. (2015). Think about your shot. Available at: http://www.beaumarisnetballclub.com.au/player-development/player-tips/think-about-your-shot/
Blazevich, A. (2010). Sports biomechanics the basics: Optimising human performance. Bloomsbury: Black Publishing.
Hede, C.& Russell, K. & Weatherby, R. ( 2011). Applying biomechanics to sport(3rd ed). New York: University of Oxford
Knusdon, D. (2007).
Fundamentals of biomechanics. Department
of Kinesiology. California Springer Publishing. 2, pp. 4-334.
Steele, J. (
1993). Biomechanical factors affecting
performance in netball. Department of Biomedical Science. 3, pp. 1-18.
