Emma Roberts and Zoe Gerasimopoulos
Sport Skill:
Major Question:
The Answer:
Drop Punt
Drop Punt
The drop punt is the most used kick in AFL used both for short and long distances. Knowing the biomechanics of this kick will help to improve technique, as well as accuracy and power. The image below demonstrates the various stages involved in a drop punt kick.
The breakdown of a drop punt kick (Barr, 2015).
1. Run Up
Utilising the use of a run up can help to serve two important biomechanical purposes, firstly to increase stability and secondly to increase force behind the ball (Aside, 2014). While it is important to have increased velocity when running, accuracy also needs to be considered.
Stability ensures accuracy of the kick. The velocity of the run should be at a steady and comfortable pace. While it is important to run up quickly to increase power behind the ball, moving at a steady pace will improve stability of the body. Inertia has an influence on running and in order to swing the legs back, and forth the inertia of the leg has to be overridden. Because of inertia, if force is not acted upon the leg, then it will remain in its own state of motion as stated by Newton’s first law “An object will remain at rest or continue to move with constant velocity as long as the net force equals zero (Blazevich, 2010, p.42). In order to run quicker the athlete needs to swing the legs back further in order to increase momentum.
In the drop punt the momentum in the kicking leg is being transferred into the ball. This means that the momentum, velocity and acceleration of the kicking leg will influence the distance the ball will travel. This force begins in the run up and begins with a push and lift motion as the foot hits the ground. When the foot hits the ground, the ground produces a reaction force. The more force produced when the foot hits the ground, and the longer its on the ground the more momentum and velocity it will produce (Blazevich, 2010). Therefore in this initial run up stage the athlete should try to run with the greatest impulse, as this will result in the an increased change of momentum. This term is known as the Impulse-Momentum relationship and helps us understand how to best move the body forward.
2. Planting the supporting leg
Planting the supporting leg provides a stable base of support for the kicking leg, as well as helping to maintain correct positioning of the hips (Aside, 2004). The foot braces the player and absorbs force generated by the initial run up (Gricho, 2013). The supporting leg as defined by Barr (2015,) provides the player with flexion, absorption and extension, which helps to provide power through the football. This is demonstrated in the image below where the importance of the supporting leg is being outlined. The image shows how the leg is transferring force from the leg to the ball.
The role of the supporting leg (Barr, 2015).
3. Ball Drop
It is important to have a correct trunk position when dropping the ball to perform a drop punt . This will allow for optimal accuracy and generation of power. If the centre of mass is too far forward in relation to the planted foot, then accuracy will be decreased as the ball is being dropped from a higher point. This means that control of the ball is decreased. Therefore, it is important that the trunk position of the ball is forward when releasing the ball to maintain control; this is evident in the first picture where the player’s body is slightly forward just as he releases the ball. The lower point at which the ball is dropped, the less time it has to move throughout the air. The vertical distance between the landing of the ball (the foot) and the release point (the hands) is decreased; hence the trajectory of the ball is improved (Blazevich, 2010). Inertia guides the ball down from the hands to the foot as it allows the ball to drop while maintaining its state of motion. As the ball drops it will maintain its angular velocity and the motion will remain the same.
The grip of the ball also has an influence on how the ball moves throughout the air. The drop punt and check side punt have very different grips altering the direction the ball will travel. As the aim of a drop punt is to kick straight ahead, the hands are placed evenly over the ball as demonstrated in the image below. Although this does not have any biomechanical principals, it has a major impact on the outcome of the kick.
Drop punt grip (Balfour, 2014)
4. Swing of the leg
Gricho (2013) explains that “The key goal of the leg swing is to increase the speed, and therefore force, of the foot during collision with the ball to exert more kinetic energy into the ball”.
The swing of the leg or foot is related to angular velocity. The angular velocity of the leg can hugely influence the distance of the kick (Millar, 2004). Angular velocity as defined by Blazevich (2010), is “the rate of change in the angle of the thrower” (p.16). This similarly applies to the leg. The faster the player swings the leg (the higher their angular velocity) the quicker, therefore further the ball will travel. If the athlete has a longer leg then they will have a faster linear foot speed and body movement velocity (Blazevich, 2010).
In order to produce greater acceleration of the ball, an increase in force and velocity is needed; ultimately increasing the distance the ball travels (Iaconis, 2014). This theory relates to Newtons second law of motion “the acceleration of an object is proportional to the net force acting on it and inversely proportional to the mass of the object: F=ma” (Blazevich, 2010, p.43). In football this means in order to increase acceleration on the ball, a bigger force needs to be applied (Blazevich, 2010).
The swing of the leg can be resemblant of a throw-like pattern, as it is effectively a moving chain of body parts otherwise known as Kinetic Chain (Blazevich, 2010). The joints of the kinetic chain extend sequentially, one after another as demonstrated in the image below.
The swing of the leg can be resemblant of a throw-like pattern, as it is effectively a moving chain of body parts otherwise known as Kinetic Chain (Blazevich, 2010). The joints of the kinetic chain extend sequentially, one after another as demonstrated in the image below.
Kinetic chain extending sequentially (Blazevich, 2010)
The swinging of the leg begins with the leg being drawn backwards rapidly, before swinging it forward. As stated previously this increases momentum in the leg, therefore power is transferred into the ball. The muscles around the hip accelerate the thigh, resulting in fast extension of the knee and high foot speed, which result in a larger force on the ball. Therefore, the speed of the foot swing will determine the distance of the football, due to a greater power generated through the summation of forces.
5. Ball to foot contact
As stated by AFL experts, the ball to foot contact is one of the most crucial elements of the football drop punt (AFLcommunityclub.com.au, 2014). Therefore, being able to perform this correctly is a must for all football players. When the foot makes contact with the ball, the ball is being produced with proportional acceleration. This is associated with Newtons second law of motion as the ball will not accelerate through the air if there is no force. The force in this instance is coming from the players foot. The ball to foot contact is demonstrated in the video below.
How to do a drop punt. (AFL AusKick, 2008)
The Magnus effect explains how the ball moves throughout the air, affected by different types of spin (Blazevich, 2010). In the drop punt kick the ball is influenced by a backspin motion as the ball is kicked on the underside of the ball. The Magnus effect shows how backspin increases the time the ball is in the air (hang time), making it an ideal kick for players (Gricho, 2013). The Magnus effect is related to Newton’s third law of “for every action there is an equal and opposite reaction” (Blazevich, 2010, p.43). Often if you kick a ball straight with no spin it can curve off to the side, this is due to another force acting upon the ball after the kick. This is often due to higher pressure being on one side of the ball (Blazevich, 2010). The shape of the football allows the players to put a tight spin on the ball, helping it to keep on its intended path. The ability to kick such a tight spin ball comes from the fact that it spins on its axis (Stem in Sports, 2015). If a player wants the ball to remain stable throughout the air then the player will spin the ball to create a torque vector through the axis of the ball (Blazevich, 2010). Every spinning object has a torque vector allowing the object to stabilise throughout the air.
Once the ball makes contact with the foot it is important that the foot is firm, with toes pointed. The ball needs a solid surface to react with. If the foot is floppy then some of the force upon contact will be lost, resulting in decreased speed. Therefore, when contact is made the player needs to make sure the ball is dropped on the middle of the foot, rather than near the toes, to produce more force. This relates to Newtons third law of action-reaction. The action is the ball moving through the air, and the reaction is the contact made between the ball and foot (Higgs, 2013).
6. Follow through after the kick.
The follow through of the kick is important as accuracy and power will be maintained with the ball throughout the air. If the player comes to an immediate stop after kicking then they may lose momentum (Higgs, 2013). The player should land on the foot they just kicked with then run through at a steady pace and slowly come to a stop or move forward to where the ball was kicked. These different aspects help with both power and accuracy of the ball.
Check Side Punt/Banana
The Check side punt, often referred to as a Banana kick is used to kick the ball sideways, often to increase accuracy when kicking for goal from difficult positions such as the boundary line near the behind posts. This can be a difficult kick to master, but if successful a very useful skill in the game of football. The video below demonstrated by Western Bulldogs star Chris Grant shows the skills and technique behind this kick including grip and angle on the ball.
As you can see in the diagram above, the ball curves around as the player is in a difficult angle to kick for goal.
1. The grip of the ball/body positioning
In a check side punt the ball is held with the right hand forward for a right foot kick, and the opposite for the left foot kick. (AFL AusKIck, 2008) The ball is placed off its centre of gravity. This is demonstrated in the image below. Unlike the set drop punt the body is not faced towards the intended target and is angled in the other direction. The nose of the ball however, is pointed downwards facing the goal (Balfour, 2014). The ball is kicked in a different direction and curves to the intended area (e.g. goal square).
AFL check side punt grip for a right foot kick (AFL Auskick, 2008).
2. Making contact
When the ball makes contact with the foot, it needs to be at an angle across the boot to create side spin. This is demonstrated in the picture below.
Foot-ball contact in a check side punt (AFL Aus Kick, 2008).
As stated in the drop punt kick, back spin on the ball results in Magnus force that creates greater hang time (vertical force) on the ball. When performing a check-side punt, it is essential to create a side spin on the ball, manipulating the Magnus force. Creating a right side spin produces high pressure to the left of the ball and low pressure to the right of the ball (Blazevich 2010). Therefore, creating a curvilinear path as a result of a side Magnus force.
Magnus force impacting the path of the check side path (Blazevich, 2010)
Magnus force is created from the amount of force applied to the ball as well as the correct positioning when making contact with the foot. The reason a check side kick is difficult to master, is because both these elements impact the magnitude and direction of the Magnus force. Therefore, for the kick to successfully hit the target the foot must contact the ball at the right position in order to produce the right amount of Magnus force (Blazevich 2007).
3. Follow through after the kick
Like the set drop punt, the follow through is essential in maintaining accuracy and power through the ball. The principals of this follow through are very similar to the drop punt follow through, but instead of running straight where their leg is pointed, the player runs to where the ball lands. Often, the check side punt is used for kicking goals, therefore if a goal is scored they will run through at a steady pace, slowly coming to a stop.
How else can this information be used?
The information provided above would be useful for football coaches, both amateur and professional in perfecting players kicking techniques. The biomechanics can be used to explain why certain techniques players are using are wrong or while optimal performance is not being achieved. Although the same skill can be performed in different ways, the basic biomechanical principals are the same.
Physical Education teachers can also use this in the higher levels (year 11 and 12) in improving technique and understanding how different biomechanical skills can be applied to various movements. Students can begin to understand different biomechanical principals (e.g. Magnus force) and relate them to specific movements in various sports.
Furthermore, the biomechanics explained in this blog can be transferred into any skill that involves a kick like action. The best example of this is soccer, as like football the kicking action is the most used skill and fundamental to the game. The soccer kick and football kick have the same basic movements such as a run up and swing of the leg and many of the same biomechanics can be applied. For example, the Magnus force used in the AFL check side punt, can also be applied in a corner kick for soccer, as they both travel along a curved path.
Reference List
AFL AusKick,. (2008). Skills - Drop Punt. Retrieved from https://www.youtube.com/watch?v=YsuzLq-n6m4
AFL AusKick,. (2008). Skills - Banana Kick. Retrieved from https://www.youtube.com/watch?v=DuaSpU8IqI8
Aflcommunityclub.com.au, (2014). AFL Community: Basic Mechanics of Kicking. [online] Available at: http://www.aflcommunityclub.com.au/index.php?id=424 [Accessed 17 June. 2014].
Aside (2014). What biomechanical principles can be applied to the effective kicking of a drop punt over distance in Australian Rules Football (AFL) consistently?. Retrieved from https://toom0011biomechanics.wordpress.com
Barr, S. (2015). What biomechanical principals apply to increase kicking distance in Australian Rules Football. Retrieved from, http://kickingbiomechanics.weebly.com
Balfour, C. (2014). How can players manipulate kicking variables in Australain Rules Football based on the dynamics of the game? Retrieved from http://balfbiomechanicsblog.weebly.com
Blazevich, A. (2010). Sports biomechanics, the basics: Optimising human performance. A&C Black
Higgs, M. (2013). How can the kicking technique in a short drop punt be optimised to maximise speed and accuracy?. Retrieved from http://michaelhiggshlpe3531.blogspot.com.au
Iaconis, n. (2014). What biomechanical principles affect the distance achieved in an AFL drop punt kick?. Retrieved from http://niacbiomechanicsblog.blogspot.com.au
Millar, J. S. (2004). Kinematics of drop punt kicking in Australian rules football-comparison of skilled and less skilled kicking (Doctoral dissertation, Victoria University).
Stem in sports. Football Learning Guide for Parents and Educators, Retrieved June 5 2015, from, https://www.connectamillionminds.com/assets/media/sis/downloads/football.pdf
