What Biomechanical Factors can improve a
Netball Goal Shooter’s Accuracy?
Amanda Fairley 2106015
Biomechanics
is a science field that studies forces and their effects on human performance. It
applies the laws of mechanics and physics to gain a greater understanding of
athletic performance through simulation, modelling and measurement (Blazevich, 2010, p.3). By understanding the principles of
biomechanics, it can improve performance by optimising human movement patterns.
This can be applied to sport skill, such as netball goal shooting. In the game
of netball, an accurate goal shooter or goal attack is vital in a team being
successful. Biomechanics can be used to identify and research any technical
error and decrease the chance of injury within the goal shooter’s technique. To
answer this question thoroughly, first we need to understand the biomechanics
of the netball shot technique.
The
biomechanical principles of the netball shot include:
· Preparatory stance
· Shooting action
· Ball release
· Ball trajectory
Does the shooter’s stance affect their
accuracy?
Preparatory Stance
Balance and stability
are important factors when it comes to performing in sport, especially netball.
An athlete’s
loss of stability can have an adverse effect on their ability to perform the
skills of the given sport (Hede, Russell & Weatherby, 2011, p. 7). Netball involves both dynamic and static
balancing. 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). A goal shooter must control their body while
it is stationary. The amount of balance
required depends on the particular activity which is being performed. This is
linked to the body’s base of support. During the netball shot, the main base of
support for the shooter is their feet, which are planted on the ground.
All humans and objects have a centre of gravity. Blazevich
(2010) states “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”. The shooter should stand with their feet,
shoulder width apart. This increases the shooter’s core stability and aligns
the centre of mass above the base of support. Excessive trunk movement during the shooting action
could hinder the stability and balance of the shooter. A study by Elliot
and Smith (1983, p. 14) found that skilled netball shooters maintained a
relatively upright trunk position, leaning backwards slightly with their head
upright and their body centred over their base of support to help produce a
balanced shooting stance. Therefore, minimal movement of the truck is preferred (Steele,
1993). Having a solid structure for balance and stability will allow for
optimal performance to execute an accurate shot at goal. This provides the shooter with the optimal
amount of stability and balance they can achieve during the shot.
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.
How can force be applied
with the optimal result?
Shooting Action
Force is listed by Blazevich (2010) as being “The product of mass and
acceleration; induces a change in the mobile state of an object.” It is anything
that has the potential to cause the movement of an object which it acts upon. 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). The tendency for an object to remain in its present state is called
inertia, often referred to as Newtons Law of Inertia. The shooter
must use force to change the inertia of the ball which is the state of rest. 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. .If a
shot is to be taken from the outer edge of the goal circle, the shooter would
to apply more force horizontally than taking a shot within a metre of the ring.
This shot would require more vertical force to achieve the sufficient angle of
release. During the shot, a shooter uses their predominant hand to push the
ball while the non-preferred hand is used as a guide. This enhances the force
of the motion while sustaining accuracy.
Figure
1.2: the sequential summation of force from body parts is essential
to maximise force production
In the netball shot, the
ball is propelled through the legs, trunk, shoulders, arms and wrist. To begin
the shot, flexing at the knees is required to ensure adequate force could be
created during the extension phase of the shooting action to propel the ball to
the goal ring (Steele, 1993). To gain a more accurate shot for goal, many
shooters tend to flex their forearm at the elbow. The optimal angle for elbow
flexed is between 90 to 104 degrees (Steele, 1993).The predominant hand is
considered the shooting hand. This hand should extend as far as possible, while
attempting to avoid hyperextension of the hand, to stabilise the ball in
preparing to shot. Consistent shooters bend their knees, shooting elbow and
flex hand at the wrist in the same motion. This simultaneous motion is used to attain the
highest degree of accuracy rather than maximum velocity (Steele, 1993).
How can the angle of
trajectory provide higher accuracy?
Projectile Motion
As previously mentioned, balance and force are two important principles of
biomechanics featured in the netball shot. Another important principle is the
projectile motion of the ball. When an object is projected through the air at an
angle, this is referred to as projectile motion (Blazevich, 2007, p. 125). In the netball shot, environmental
factors like gravity and air resistance can affect the motion of the ball. The
speed of the projection object will be determined by height it reaches before
gravity accelerates in back down to earth (Blazevich, 2010). Besides
these, the trajectory of the ball is influenced by three biomechanical factors,
the projection speed, the projection angle and the distance between the thrower’s release point
and the height in which it must reach. The maximal distance the object will travel is
partly determined by the angle of projection. When the angle is greater, the
object attains a greater vertical height but will not travel as far. It has
been found that the average release angle in a netball shot is between 58 and
60 degrees from the horizontal (Elliot and Smith (1983, p. 7). However this can
be altered when facing a tall defender defending the shot.
When attempting to improve accuracy, the relative height of projection is
also important. 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. By aiming high, this
also 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. Once a
projectile has been released, its horizontal velocity remains constant for the
duration of its flight. Steele (1993) implies the average angle of
entry of a ball through the goal ring is 43.1 degrees. This angle of the shot
was proven to be optimal due for the tolerance for error. When a
shooter is close to the goal post the projectile motion is 90 degrees vertical
and zero degrees horizontal.
Follow Through
Figure 1.3 (Knusdon,
2007, p. 7)
When a
projectile is thrown, specific techniques are used to cause the projectile to
spin. As shown in Figure 1.6, the Magnus effect occurs when a spinning object
is moving through air. 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).
How does understanding these biomechanical principles assist to how a
netball shooter can improve their shooting accuracy?
The Answer
When considering the above information it can be
summarised as:
Preparatory When preparing to shoot, the foot corresponding to the shooting side of the body should be placed marginally forward or both feet are aligned to point directly at the goal ring. The feet are to be spaced approximately shoulder width apart and directly under the centre of the body. The knees should also be slightly bent. This foot placement improves accuracy by providing a stable base support which helps to minimise 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 and balance.
Flexing at
the knees is essential to ensure adequate force is produced during extension
phase of the shooting action to propel the ball up and into the goal ring.
Athletes must be able to control the amount of force and the direction of it
during the shooting action. To improve accuracy, the shooter should flex the
elbow and sufficiently, without hyperextension, extend the hall to stabilise
the ball.
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.
Angle of
Release/ Projectile Motion
When attempting
a shot close to the ring, the athlete needs to shoot 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.
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.
Also to
enhance the accuracy of the netball shot, shooters should attempt to receive
the as close to the goal ring as possible before taking their shot. The closer
they are, the more accurate they are likely to be. A study by Elliot and Smith (1983)
found that the most preferable distance was between 0.9m and 1.5m from the post.
Where else can we use this information?
The shooting
technique is used 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, 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.
Conclusion
After
investigating the biomechanical principles related to netball goal shooting, we
can use this information to improve the accuracy and work toward optimal
performance in sport. Understanding movement is an essential part of physical
education, for not only acquiring skills, but understanding concepts and game
awareness. In the game of netball, understanding movement is essential to successful
performance, especially when it comes to being an accurate goal shooter or
attack. 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.
(2007). Sports biomechanics the basics: Optimising human
performance. Bloomsbury Black Publishing.
Blazevich,
A. (2010). Sports biomechanics the basics: Optimising human
performance. Bloomsbury: Black Publishing.
Elliot,
B. and Smith, J. (1983). The relationship of selected biomechanical and
anthropometric measures to accuracy in netball shooting. Journal of Human
Movement Studies. 9:171-187.
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.
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