Jobe
Watson handballing
The handball skill in Australian Football is one of two main
methods of disposing the ball. Handball
is an important skill in today’s game, allowing individuals to pass the ball
accurately, quickly and effectively down the ground to team mates to score, whilst
catching the opposition off guard (Australian Football League, 2009). It is vital handball is performed effectively
and efficiently with optimal force, placing the ball in a position for team
mates to receive easily without changing momentum (Marano, 2013). This can be determined by considering a range
of biomechanical factors such as summation of forces, the kinetic chain and
projectile motion.
The
Answer
Figure 1: Summation of forces for the handball
Figure 2: Standing still handball
Where is the best part of the ball to make contact with and why?
For an accurate and powerful handball, it is best to strike the
ball at the cross made by the seams at both ends of the ball, with stitching on
top (Figure 3) (aussierulesuk, 2008) . Striking the ball at the cross is perfect because
it’s the smallest surface area, allowing an individual to have more control
over the handball technique (United States Australian Football League) .
The shape of an AFL football is oval. Therefore, the accuracy within a handball is
largely affected by its centre of mass. The
centre of mass is located through the seams of the ball. Centre of mass allows the football to travel
with accuracy aiming and reaching its correct target. This can be explained by the ball having larger
coefficient restitution at the side of the ball and a smaller coefficient
restitution that meets at the four seams at each end (Blazevich, 2010) .
As a result, the ball has more power when striking it on its side but will
usually have less accuracy as the surface area of the ball is much larger than
the side of the hand striking it.
This is the opposite effect when contact is made at the point of
the ball where the seams meet. Why?
Because the ball has a smaller coefficient of restitution that will decrease
the power of the handpass due to the point of impact having a smaller surface
area. The striking hand contacting the
point of the ball is closer in size; which allows the ball to travel on a
trajectory with more suitable accuracy (Blazevich, 2010) .
Therefore, the centre of mass is highly desirable for an accurate
handball because of the seams located through the ball. As a result, striking the ball at the seams allows
the ball to spin backwards in the path of the handballer but moves
forward. This technique is most
effective when delivering the ball through the air because of less air
resistance. Less air resistance causes
the football to drop or rise but allows for spinning, which is most effective
and simplest way for a team mate to catch (Blazevich, 2010) .
Figure 3: Seems of the ball
What is the optimal release for ball trajectory and why?
In Australian Rules football a handball can be executed in a
number of ways. While the standing
position is the most ideal way to complete the skill, handball can also be
executed whilst players are prone on their front or back as well from a kneeing
stance (figure 4) (Australian Football League, 2009) . The optimal angle of release for a projectile
to cover the greatest distance is 45 degrees from ground level (Blazevich, 2010) . Why? Because a projectile released at a
higher or lower angle will decrease the distance travelled. A higher trajectory will travel higher and
shorter and a lower trajectory will travel lower and fall to the ground due to
gravity. Therefore, it is important to
perform a handball with an optimal angle of release at approximately 43-44
degrees with the ball held 1 metre above ground level (Blazevich, 2010) .
However, the technique and physical characteristics of an athlete will
determine the height of the delivery point.
Projectiles are affected by several external influences that
include gravity, drag force and air resistance.
These external influences are the reason projectiles, which in this case
the AFL football either rise or fall and potentially move from side to
side. Drag force affects a football when
fluid air molecules are present and causes the projectile to lose kinetic
energy with reducing the amount of velocity on the projectile (Blazevich, 2010) . The laminar flow is the flow of air that is constant
and travels in the opposite direction to the projectile. Laminar flow passes over and around the
object as seen in figure 5. After the
air is passed over the projectile, the flow becomes non-laminar which changes
the direction of air flow. Non-laminar
flow is also called turbulent flow. The
change of air flow causes the projectile to lose energy but turbulent air flow
allows the projectile to gain energy. Gravity
is a natural force that constantly affects a projectile. An example of this is gravity pulls the
projectile down to the earth’s surface (Blazevich, 2010) .
Figure 5: Laminar Air Flow
How
else can we use this information?
Force of
summation and kinetic chain
Force summation and kinetic chain is useful information that can
be used when teaching an individual skill and technique. Each individual is diverse and has different
levels of strength and physiological appearance. For example when some individuals perform the
shot put action, they may find using a push like technique will be easier to
perform whilst others may find a chest-pass technique is simpler (Blazevich, 2010) .
Coefficient
of restitution
Another way the coefficient of restitution can be explained is
reducing the impact of collisions to improve and reduce injuries. An
example is gridiron is using padding as this will reduce energy imparted whilst
helping improve the dissipation of energy to reduce the impact of
collisions. Another implication of the
coefficient of restitution is to improve tactical thinking of coaches and
managers. Why? Because in wet conditions
on field sports a greater energy must be imparted into the ground to get the
same rebound and output as if in playing in dry conditions. If this tactical thinking is implemented an
attacking team will play a style of sport that will reduce their need to
run. Therefore, this tactical thinking
will see the oppositions legs become fatigued (Blazevich, 2010) .
Angle of
release
The angle of release at 45° is not always possible as an individual’s
technique and physical attributes will cause the optimal angle to change as the
position of the projectile is released.
If the athlete can get a higher velocity at a lower angle, then there
has to be a trade-off between the optimum release angle and maximum release
velocity. In soccer it is believed that
the optimal angle of release for a throw in after the ball has been kicked out
is approximately 30° (Blazevich, 2010) .
Centre of
mass
The centre of mass can be manipulated in other sports to evade
opponents when the player is carrying the ball down the field. It can also be manipulated when having a jump
shot in basketball when the player raises their body of the ground in what’s
known as the ‘hang’ phase. The ‘hang’
causes the centre of mass to rise and become centred. The balanced body allows for the shot to be
performed with an already upward force as the upper body momentarily remains stationary
in the air (Blazevich, 2010) .
Drag
The information relating to drag can be useful in most sports that
require a projectile to be either thrown or kicked. This is also useful in creating clothing and
trying to gain an advantage in making individuals performance better through
the use of aerodynamics. Drag has been
tested by many sporting experts and it is now known that oval shaped balls can
reduce the amount of drag in flight by imparting the ball with a spiral spin so
that the ball remains stable and can create what’s known as a ‘torque vector’ (Blazevich, 2010)
References
aussierulesuk. (2008, January 2). AFL Skills Video -
Handball Pass [video file]. Retrieved March 29, 2014, from
http://www.youtube.com/watch?v=Do2plgdfYYw&NR=1&feature=endscreen
Australian Football
League. (2009). NAB AFL Auskick. Skills Guide, 61. Retrieved April 8,
2014, from
<http://www.afl.com.au/portals/0/afl_docs/development/coaching/junior_manual/AFL_Junior_Coaching_Manual_5.pdf>
Blazevich, A. J.
(2010). Sports Biomechanics, The Basics: Optimising human performance
(2nd ed.). London: Bloomsbury.
Marano, J. (2013). Biomechanically
what is the most effective way to improve the accuracy and power in an AFL
Handball. Retrieved March 29, 2014, from Blogger: www.biomechanics-handball.blogspot.com.au/
Parrington, L., Ball,
K., MacMahon, C., & Taylor, S. (2009). Biomechanical analysis of the
handball in Australian Football. School of Sport and Exercise Science.
United States
Australian Football League. (n.d.). Handball and Types of Handball.
Retrieved from Us Footy: http://www.usfooty.com