THE BIOMECHANICS OF THE AFL HANDBALL

 

The skill of the Australian Rules Football (AFL) Handball plays an important part in the game as it allows individuals to pass the ball quickly and effectively, down the ground, to teammates and as well as clear an area away from the other team. Therefore it is important that the skill of the handball is most effective and efficient, so that it can be performed with the optimal force and placed in a position that is accurate for their teammate to receive or collect the ball without being made to change their momentum.

 

THE ANSWER
 “How can force summation be used to impart the greatest velocity on the ball?”

 

 

 

 fig1. Summation of forces for the handball

 

Force summation or the kinetic chain can be imparted into the football through the hand allowing the ball to travel a greater distance than if a force came from a single movement. The simplest way to explain the concept of summation of forces is that a sequence of forces are added together to create a larger force, this differs from a single force in that it is created from one large force. A summation of forces begins with the larger muscle movements and flowing to the smaller muscles to the point of its release. In the image above (fig. 1) from 'Biomechanical Analysis of the Handball in Australian Football'  (Lucy Parrington, Kevin Ball, et al. 2009) , the sketch is holding the ball in the palm of their left hand placing the ball on a platform (therealglenoxo. 2008) and then taking a step forward (large muscles) with their left leg, then pulling back their right hand/ arm away from the ball in the backswing phase, they are then rocking back onto their right leg and starting to move their momentum forward with their right arm starting to come forward. The next phase has the body moving forward with the legs and torso as well as right arm all meeting the ball at the same time to create a massive force from the summation of forces beginning at the legs, moving up through the torso, then onto the upper arm and down the arm to the hand which strikes the ball. This large generation of force coming through the larger muscles to the smaller muscles and then into the ball allows the ball to travel greater distances as opposed to a handball that is done by just standing flatfooted without and forward movement from the legs (fig. 2). This summation of force will allow an individual to increase the power imparted into their movement and handball allowing them to handball further or at greater speed, this can also have a detrimental effect on their accuracy as their handball as the body is moving more(Blazevich, A. 2010).

fig 2. Standing handball

 “Where is the best part of the ball to make contact with and why?”

The best part of the ball to hit to receive the most accurate and powerful handball is at the cross made by the seams of the ball at either end, preferably you would have the stitching on the top of the ball (fig. 3).

fig 3. Handball positioning

This is the most accurate part of the ball to hit as it has the smallest surface area and allows you to have the greatest control over the handpass technique. An AFL football is of an oval shape, the accuracy of the handball is largely affected by its centre of mass which is located through the seams of the ball as seen in figure 4, the centre of mass on the ball will allow it to travel with accuracy and in the desired fashion. This means that the ball has a larger coefficient of restitution at the side of the ball and has a smaller coefficient of restitution at the meeting of the four seams at either end (Blazevich, A. 2010). Therefore the ball will have more power when hitting the ball on its side, however the ball will 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 hitting the point of the ball where the seams meet as the ball has a smaller coefficient of restitution which will decrease the power of the handpass, but the point of impact has a smaller surface area. The hand striking the point of the ball is closer to equal size, this will allow the ball to travel on a trajectory and an accuracy that is much more desirable. The accuracy of the handball is largely affected by its centre of mass which is located through the seams of the ball; the centre of mass on the ball will allow it to travel with accuracy and in the desired fashion. Hitting the ball at the cross on the ball, will cause the ball to spin backwards in the direction of the handballer while still travelling forwards, this is the most effective way for the ball to move through the air as when it travels through the air it is less affected by air resistance, which will cause the ball to travel at a different angle or can cause it to drop or rise. This is also the most effective and simplest type of spinning ball to catch.

fig 4. Centre of mass of AFL football

 

“What is the optimal release trajectory and why?”

 

 

 

fig 5. Projectile motion and moptimal angle of release

In Australian Rules football there are a number of different positions a handball can be completed from, as long as both arms/hands are free a hand pass can be completed, the most likely position to complete the skill is from a standing position. The optimal angle of release for a projectile to cover the greatest distance as seen in figure 4 above is 45^o from ground level (Blazevich, A. 2010); this is because if a projectile is released at a higher or lower angle there will be a decrease in the distance travelled as higher trajectory will travel higher and shorter and lower will travel at a lower trajectory and will drop due to gravity (fig. 4). For a hand pass, the ball is already approximately 1 metre above the ground level when its being performed therefore the optimal angle of release is approximately 43-44^o. However technique and physical attributes of the athlete will change as well as the position the ball is being handballed from, 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.

Projectiles are affected by a number of outside influences including; gravity, drag force and air resistance. These influences can cause the projectile in this case the football to rise or fall and potentially move from side to side. Drag force will affect a football when there are fluid air molecules; drag force will cause the projectile to lose kinetic energy and will reduce the amount of velocity on the projectile (Blazevich, A. 2010). The laminar flow is the flow of air that is constant and travels in the opposite direction to the projectile, it passes over and around the object as seen in figure 6. The air after it passed over the projectile becomes non-laminar flow or turbulent flow, this change of air flow causes the projectile to lose energy and the now turbulent air to gain energy. Gravity is a natural force that is constantly in effect, it's a downward force that affects projectiles by pulling them down back to the earth's surface.

fig 6. Drag force acting upon a projectile

How else can we use this information?

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, A. 2010).

Force Summation/Kinetic Chain- Useful information about force summation and Kinetic chain are that when teaching each individual is different and has a different level of strength or different physiological make up. Therefore some individuals in regards to shot put may find it easier to use a push technique, while others may find it simpler to perform a chest-pass technique (Blazevich, A. 2010).

Coefficient of Restitution- information regarding the coefficient of restitution can be useful in reducing the impact of collisions to improve safety and reduce injuries. Some implications in the improvement of safety measures are improved padding that will reduce the energy imparted and help improve the dissipation of energy to reduce the impact of collisions. Another useful implication of the coefficient of restitution would be the improvement of tactical thinking of coaches and managers, as in wet conditions on field sports a larger energy must be imparted in the ground to get the same rebound and output as if in playing in dry conditions, so then the opposition's legs will become fatigued or play a style of sport that will reduce their need to run (Blazevich, A. 2010).

Angle of Release- useful information in its application is not always at 45^o as an individual's technique and physical attributes will cause the optimal angle of release to change as the position the projectile is being released from. 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^o (Blazevich, A. 2010) .

Centre of Mass- Centre of mass can be manipulated in other sports to evade opponents when you are carrying the ball down the field, it can also be manipulated when having a jump shot in basketball when you raise your body off the ground and are 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, A. 2010).

References

Lucy Parrington, Kevin Ball, Clare MacMahon and Simon Taylor, 2009, Biomechanical Analysis of the Handball in Australian Football, School of Sport and Exercise Science, Victoria University, Melbourne, Australia

 

therealglenoxo. (2008 January 2). AFL Skills Video - Hand Pass [video file]. retrieved from http://www.youtube.com/watch?v=Do2plgdfYYw&NR=1&feature=endscreen

Australian Rules Football League, 2009, NAB AFL Auskick, Section 5 - skills guide, page 61
http://mm.afl.com.au/portals/0/afl_docs/development/coaching/junior_manual/AFL_Junior_Coaching_Manual_5.pdf

Blazevich, A. (2010). Sports biomechanics, the basics: Optimising human performance. A&C Black.