Biomechanics is the sport science field that applies the laws of mechanics and physics to human performance, in order to gain greater understand of performance in athletic events through modelling, simulation and measurement (Blazevich, 2010, p. 3). In relation to the game netball accurate shooting is critical to the success of the netball team. To answer this question properly we first need to identify and understand the biomechanics of this activity.
Preparation of the netball shot
Figure 1.1 shows how the body’s centre of gravity can shift depending on the body’s movement and position. When shooting a goal in netball often the athlete is in a static position meaning when the body is at rest (Blazevich, 2007, p. 125). It is important to note, however, that a body may be stable in one direction but not in another. For this reason, it is essential to consider the orientation of the base support to the force being applied. For example as there is not much force needed to shoot the netball the athlete will only have their feet shoulders width apart, however, a wrestler for example wanting to prevent being pushed back will brace himself by placing his feet in a wide stance and having one foot behind the other (Hede et al., 2011, p. 7). A study by Elliot and Smith (1983, p. 14) found that skilled netball shooters also maintained a relatively upright trunk position, leaning backwards slightly with their head upright and cantered in the midline of the body to help a balanced shooting stance.
How close to the ring ?
Another aspect to consider when shooting the netball is the
distance the player is from the netball ring. Often netball players are aware
of their shooting percentages over different distance ranges (Steele, 1993, p.
4). The further away the netballer is to the ring the less chance they will
have of getting it in. As the netballer is further away from the ring they need
to demonstrate greater flexion of the knees and shooting elbow to create more
force while also increasing release height and greater velocity (Steele, 1993,
p. 5). Shooting goals further from the post required changes in the mechanics
of the shooting action. These technique changes may account for the loss of
accuracy in the longer shots (Knusdon, 2007, p).
Shooting Action
Force is anything that causes or has the potential to cause
the movement, diversion or slowing of the object on which it acts. This relates
to Newton’s second law, the acceleration of an object is proportional to the
net force acting on it and inversely proportional to the mass of the object (Blazevich, 2007, p. 125). All forces have four common properties, magnitude, direction, a point of application and a line of action.
Figure 1.2 ( Knudson, 2007, p.7)
Figure 1.5
Projectile motion
From the above information we now know that balance and
force are two important biomechanic principles when shooting netball. However the projectile motion of the netball
shot is also important. Projectile motion refers to the motion of an object
projected at an angle into the air(Blazevich, 2007, p. 125). The angle of projection is an important factor
affecting the projectile range. If an object is projected vertically, it will
land back as its starting point, after gravity has pulled it back to earth. The
maximal range of projectile is determined partly by its angle of projection.
When the angle is greater the object attains a great vertical height but lesser
range. A study done by Elliot and Smith (1983, p. 7 ) found that the average
angle of release in netball shooting equalled 59.8 degrees from the
horizontal. The release of the netball would slightly be above 45 degrees and between 70
degrees. However, it also depends on the
height of the defender this effects the angle of realise. As you can see in figure 1.6 the defender from Victor Harbor netball club is very tall. The Netballer must project the ball with greater angle and veloicty height to aviod the netballers hand.
The relative height of projection is also important when trying to improve accuracy of the netball shot. The height of projection is the vertical distance between the projection point of an object and the point at which it ands ( Blazevich, 2007, p. 130). When shooting the netball close to the ring players need to project the ball with maximum vertical velocity the netball will therefore not travel horizontally over the ring (Blazevich, 2007, p. 125). A high release of the ball contributes to accuracy as it also shortens the pathway the ball has to travel to reach the goal ring. Once a projectile has been released, its horizontal velocity remains constant for the duration of its flight.
Often when a projectile is thrown, techniques are used to cause the projectile to spin. The Magnus effect occurs when a spinning object is moving through air or water, this can be seen in figure 1.6. As
shooting a netball is more about accuracy often netballers decrease the release
speed placing more emphasis on perfecting the angle and height of release (Blazevich, 2007, p. 125). However,
a study by Elliot and Smith (1983, p. 5) found that skilled netballers implied
a small amount of backspin to increase the entry angle of the ball to rebound
off the ring into the net. This is because when a spinning ball bounces, it
always bounces in the direction of the sin on the ball. A backspin on the ball
tends to make it bounce backwards into the net.
The Anwser
How does understanding all this allow us to determine how a
goalie can improve the accuracy of her netball shot? The factors we need to
consider when working out how a netballer can improve the accuracy of her
netball shot can be summarised as:
- Preparation:
In preparing to shot place the foot corresponding to the shooting side of the body either slightly forward or aligned both feet parallel to point directly at the goal ring, spaced approximately shoulder width apart or less. The knees should also be slightly bent. This foot placement facilities accuracy by providing a stable base support minimising trunk rotation. The centre of gravity is lowered by slightly bending the knees assisting the base of the support even more.
Implications: minimise head and trunk movement while preparing to shoot to ensure stability.
To enhance the accuracy of the netball shot athletes should be encourage to manoeuvre the ball as close to the goal ring as possible before shooting. A study by Elliot and Smith ( 1983) found that preferable between 0.9m and 1.5m from the post was the best spot for improved accuracy.
- Shooting action:
Flexing or sinking at the knees is
necessary to ensure sufficient force can be generated during the subsequent
extension phase of the shooting action to propel the ball to the goal ring. As already stated athletes must be able to
control both the amount and direction of force produced during the shooting
motion. Therefore to improve accuracy the netballer should slightly flex the
elbow, sufficient but not excessive hypertension of the hand to stabilise the ball,
minimisation of trunk, arm and forearm movements during the shooting action in
favour of increased hand motion, creating greater force for the release height
and release velocity.
Implications: To improve shooting accuracy players should extend shooting hand only as far as necessary , avoid hypertension of the hand at the wrist and decrease movement of the trunk and forearm is recommended in the shooting motion.
Implications: To improve shooting accuracy players should extend shooting hand only as far as necessary , avoid hypertension of the hand at the wrist and decrease movement of the trunk and forearm is recommended in the shooting motion.
- Projectile motion
To improve accuracy of the netball shot
when close to the ring, the athlete needs to shot the ball at a greater angle
to attain greater vertical height and less range. The relative height of
projection is also important. The athlete needs to project the ball with
maximum vertical velocity. A high release of the ball contributes to accuracy
as it shortens the pathway the ball has to travel to reach the goal range.
The Magnus effect occurs when a spinning
object is moving through air or water. To improve the accuracy of the netball
shot the athlete should use backspin to assist the flight direction. It also
reduces the ball speed impact with the goal ring which, in turn provides better
opportunity for the ball to rebound off the ring and into the net. Wrist
Flexibility can be modifies through using appropriate training exercises.
Implications: Release
height in shooting could be improved by increasing extension at the knees and
at the elbow of the shooting arm. Optimal shot for goal would be realised at an
angle of approximately 60degrees, with a backward spin of 1 to 1.5 revolutions
in relation to its direction of travel.
How else can we use this information
We see this shooting technique in many other sports.
In basketball, and other throwing games accuracy is vital to the success of the
game. We can now use our understanding of the biomechanical principles such as
balance, summation of forces, Magnus effect and projectile motion to improve
performance in other sports. For example in cricket the bowler’s main aim to is
bowl the ball with the correct angle of release, height of release and enough
force to get the batter out.
References
Blazevich, A. (2007). 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, 4-334.
Steele, J. ( 1993). Biomechanical factors affecting performance in netball. Department
of Biomedical Science. 3, 1-18.
