Australian Rules Football is a complex game consisting of multiple movement problems, all of which require the successful execution of a variety of functional movement solutions (Davids, Button, & Bennett, 2008). As kicking is fundamental to the game of Australian Rules Football (Ball, 2008), the ability to alter the kick to meet the demands of the game, therefore becomes vital. This blog will first analyse the biomechanics associated with a typical kicking pattern and will then discuss how adjustments to grip, angle of release, and angle of collision can be manipulated to solve movement problems during game situations.
BIOMECHANICAL ANALYSIS OF A 'TYPICAL' KICKING PATTERN
A typical kicking pattern mostly occurs on the sagittal plane (Blazevich, 2012; Pedler, 2012). However, as the kick is a whole-body movement, there are moments when different segments operate on the frontal and horizontal planes (Rath, 2000). This skill is described as a throw-like movement characterised as an open kinetic chain movement (Blazevich, 2012). Momentum is generated through the proximal segments, and then sequentially transferred to the distal segments. As a result of this kinetic chain, momentum is transferred systematically to the foot, producing a high-end velocity (Blazevich, 2012).
RUN UP AND BACKSWING
The backswing starts when the toe leaves the ground after the final step. Through rotating the hip and pelvis to create a maximum hip angle, the distal segments are further away from the axis of rotation (Blazevich, 2012). Therefore, shank and foot segments have more time to accelerate before ball contact.
Please note: Decreasing the hip angle will decrease the velocity of distal segments, therefore decreasing the force applied to the ball.
WIND UP
During the wind up phase a minimum knee angle (maximum knee flexion) is created, resulted in a maximum shank angle (refer to figure 2) (Pedler, 2012). This simultaneously occurs as the thigh moves forwards while the shank moves backwards (Kellis & Katis, 2007). By creating this tight knee angle between the shank and the thigh, the radius of gyration is therefore closer to the axis of rotation, thereby decreasing the moment of inertia (Blazevich, 2012). Angular velocity is created as the thigh begins to move forwards (Kellis & Katis, 2007).
Please note: The larger the knee angle (radius of gyration is further away from the axis of rotation), will increase the moment of inertia, which will decrease the acceleration of the shank and foot segments.
FOWARD SWING
The pelvis and hip continue to rotate forwards during the forward swing, reducing the hip angle and resulting in flexion of the hip (refer to figure 2). As the thigh segment reaches maximum angular velocity, the knee starts to extend, subsequently resulting in increased shank angular velocity. Kellis and Katis (2007) discuss that the angular velocity of the thigh and shank are equal at the point at which the knee starts to extend. Towards the end of the forward swing phase, the hip of the kicking leg is at maximum flexion as it comes to the end of its movement plane. As a result, the angular velocity of the shank increases, while the angular velocity of the thigh decreases (summation of forces). Just before ball contact, the angular velocity of the thigh dramatically decreases while the shank and foot segments reach maximum angular velocity (Blazevich, 2012; Kellis & Katis, 2007).
Please note: The final angular velocity of the foot segment, is then ultimately dependent on the force produced by the proximal segments.
Please note: The final angular velocity of the foot segment, is then ultimately dependent on the force produced by the proximal segments.
BALL CONTACT
During the ball contact stage the pelvis rotates above the supporting leg, and the head is in line with the supporting foot (Rath, 2000). Through doing so, the player is able to evenly distribute their centre of mass, allowing for a greater base of support (Blazevich, 2012). During this phase the knee angle of the support leg is also slightly flexed, lowering the centre of gravity, further increasing stability (Dichiera et al., 2006).
While the foot has the potential to transfer the velocity to the ball (Young & Rath, 2011), this is dependent on the quality of contact with the ball. The coefficient of restitution (COR) of a football is typically 0.8 (Cross, 2010.), meaning that approximately 80% of energy will remain with the ball after the collision (Blazevich, 2012). However, because the football is an oval shape, the distance the ball will travel will ultimately depend on the angle of collision and the force applied to the ball (Young & Rath, 2011). In order to contact the ball with greater momentum, the foot should be plantar flexed and stiff.
While the foot has the potential to transfer the velocity to the ball (Young & Rath, 2011), this is dependent on the quality of contact with the ball. The coefficient of restitution (COR) of a football is typically 0.8 (Cross, 2010.), meaning that approximately 80% of energy will remain with the ball after the collision (Blazevich, 2012). However, because the football is an oval shape, the distance the ball will travel will ultimately depend on the angle of collision and the force applied to the ball (Young & Rath, 2011). In order to contact the ball with greater momentum, the foot should be plantar flexed and stiff.
FOLLOW THROUGH
Follow through is important for injury prevention as well as the successful execution of a kick (Orchard, 1999; Rath, 2000). Swinging the kicking leg through after contact with the ball helps to slowly dispel the momentum that was built up through the kinetic chain (Blazevich, 2012). If the body were to suddenly stop, muscles, bones, ligaments and tendons would be under a lot of strain to overcome the momentum.
Please note: Because the production of force is greater for a long distance kick, greater leg swings (during follow through) are required for longer kicks.
Please note: Because the production of force is greater for a long distance kick, greater leg swings (during follow through) are required for longer kicks.
AERODYNAMICS
The ball can experience both lateral and longitudinal motion after ball contact (Alam et al., 2009). As illustrated in figure 3, 'perfect' longitudinal rotation occurs at a spin axis of 0 degrees, while 'perfect' lateral rotations occurs at a spin axis of 90 degrees (Fuss, Smith, & Leali, 2013).
HOW Can physical educators build on from these principles based on the dynamics of a game?
While all kicks in Australian Rules Football utilise the same kicking pattern outlined above, the angle of collision and force applied to the ball will ultimately impact the flight path of the kick and the subsequent outcome of the kick. As force production, is central to this equation, the kicking pattern above can be manipulated to produce more or less force (please refer to the please note additions above). The second part of this blog will now explore how adjustments to grip, angle of release and angle of collision can be manipulated to solve movement problems during game situations. With the aim to inform practice environments and instructions within an education or coaching setting, suggested skill cues will also be provided.
how can a player quickly execute an accurate kick to another player down the mid-field?
The drop punt is the preferred kick in Australian Rules Football (Millar, 2004; Orchard, 1999) due to its accuracy, distance and speed of execution (Ball, 2008). For this reason the drop punt is commonly used for goal kicking and passing down the field (Millar, 2004).
The drop-punt is the most accurate kick due to its end over end spinning torque action (Fuss, Smith, & Leali, 2013). This spinning motion (refer to figure 4) provides the ball with a torque vector, consequently providing the ball with angular momentum (Blazevich, 2012). As the ball is spinning through the air, the laminar air flow is separated, consequently resulting in a pressure difference (Blazevich, 2012). Because the ball has backspin, air particles attach to the ball (as a result of friction) creating a boundary layer (Blazevich, 2012). As the air particles are only being ‘grabbed’ from one side of the ball, a difference in air flow becomes present. Due to the difference in air pressure, a ball with backspin will create vertical-perpendicular force that lifts the ball higher into the air. This is referred to as a Magnus force.
Based on these principles, the collision between the ball and the foot must result in backspin. In order to create backspin, the following skill cues apply:-
1) The ball is gripped either side of the laces (refer to figure 4). WHY: to prepare to kick the football on the base of the longitudinal axis.
2) Release the ball with the laces (of the ball) facing in the direction of the intended kick (longitudinal axis - vertical). Why: so the foot contacts the ball on the longitudinal axis and travels in the intended direction.
3) Aim to kick the ball on the boot laces, on the base of the longitudinal axis. Why: to give the ball backspin.
Please note: The number of approach steps and force applied to the ball will depend on the length of the kick and task constraints posed by the context of the game. For example, if more force is required, then a larger final step (greater hip angle during backswing), a tighter wind up (smaller knee angle during wind up) and a greater follow through swing would be required.
Based on these principles, the collision between the ball and the foot must result in backspin. In order to create backspin, the following skill cues apply:-
1) The ball is gripped either side of the laces (refer to figure 4). WHY: to prepare to kick the football on the base of the longitudinal axis.
2) Release the ball with the laces (of the ball) facing in the direction of the intended kick (longitudinal axis - vertical). Why: so the foot contacts the ball on the longitudinal axis and travels in the intended direction.
3) Aim to kick the ball on the boot laces, on the base of the longitudinal axis. Why: to give the ball backspin.
Please note: The number of approach steps and force applied to the ball will depend on the length of the kick and task constraints posed by the context of the game. For example, if more force is required, then a larger final step (greater hip angle during backswing), a tighter wind up (smaller knee angle during wind up) and a greater follow through swing would be required.
how can a player kick a ball to cover the most distance on the field?
As illustrated during the video below (AFLVideos2011's channel, 2011), long distance kicks were used to kick out from full-back (Ben Graham), as well as kicking goals from a long distance (Sav Rocca).
The ball was able to reach this range because the ball was projected at a 45 degree angle, providing the ball with equal vertical and horizontal velocity (Blazevich, 2012). As the ball was travelling with its longitudinal axis pointing in the direction of the flight (Blazevich, 2012), the ball experienced less drag forces, consequently allowing the ball to retain more kinetic energy and travel further than a drop punt (Blazevich, 2012). The ball was able to 'cut' through the air and stabilise in flight, due to the torque vector that was created because the ball was spinning on its longitudinal axis (spin axis close to 0 degrees).
In addition, a sufficient amount of force was applied to the ball. When considering Newton's second law of motion (F = m x a) (Blazevich, 2012), and with the assumption that we are unable to increase the mass of the leg, acceleration therefore needs to be increased. In comparison to a short-distance kick, the proximal to distal kinetic chain needs to produce a greater amount of angular velocity (Young & Rath, 2011). Therefore, during the backswing and wind up phase, greater hip and tighter knee angles are required in order to provide the thigh, shank and foot segments with more time to build up acceleration. As a result, more force is then applied to the ball, thereby impacting the distance the ball will travel. During the follow through phase, the leg will naturally swing up higher in order to compensate for the increased momentum.
Based on these distinguishing factors, a physical educator or coach might choose to adopt the following coaching cues to help their students or players perform a long distance kick.
1) Face in the direction of the target. Why: to produce linear momentum during run-up.
2) For a right foot kick, left hand should be slightly forwards on the ball, with the right hand towards the nose of the ball (as illustrated in figure 5). Use the right hand to hold the ball with the left hand to support the ball. Why: to prepare to drop the ball from the correct angle.
3) Decreased knee angle during wind up phase. Why: to decrease moment of inertia (radius of gyration closer to axis of rotation).
4) Larger final step strides. Why: to increase the length between thigh, shank and foot segments with axis of rotation (more time to accelerate).
5) Drop the ball down so that it contacts the ball on the same angle. Why: so the ball travels on its longitudinal axis.
6) Follow the ball through with a high leg swing. Why: to reduce chance of injury, and to dispel momentum AFTER ball contact.
In addition, a sufficient amount of force was applied to the ball. When considering Newton's second law of motion (F = m x a) (Blazevich, 2012), and with the assumption that we are unable to increase the mass of the leg, acceleration therefore needs to be increased. In comparison to a short-distance kick, the proximal to distal kinetic chain needs to produce a greater amount of angular velocity (Young & Rath, 2011). Therefore, during the backswing and wind up phase, greater hip and tighter knee angles are required in order to provide the thigh, shank and foot segments with more time to build up acceleration. As a result, more force is then applied to the ball, thereby impacting the distance the ball will travel. During the follow through phase, the leg will naturally swing up higher in order to compensate for the increased momentum.
Based on these distinguishing factors, a physical educator or coach might choose to adopt the following coaching cues to help their students or players perform a long distance kick.
1) Face in the direction of the target. Why: to produce linear momentum during run-up.
2) For a right foot kick, left hand should be slightly forwards on the ball, with the right hand towards the nose of the ball (as illustrated in figure 5). Use the right hand to hold the ball with the left hand to support the ball. Why: to prepare to drop the ball from the correct angle.
3) Decreased knee angle during wind up phase. Why: to decrease moment of inertia (radius of gyration closer to axis of rotation).
4) Larger final step strides. Why: to increase the length between thigh, shank and foot segments with axis of rotation (more time to accelerate).
5) Drop the ball down so that it contacts the ball on the same angle. Why: so the ball travels on its longitudinal axis.
6) Follow the ball through with a high leg swing. Why: to reduce chance of injury, and to dispel momentum AFTER ball contact.
how can a player kick a football when they are shooting for a set shot on a tight acute angle?
The situation illustrated in figure 6, emphasises a movement problem, which requires a perfect 30 degree angle kick, or a kick that can send the ball in a curvilinear-clockwise direction (McLester & Pierre, 2007). As demonstrated by Taylor Walker in the video below (Adelaide Football Club, 2011), the banana kick (also known as the checkside punt) is often the preferred kick to solve this movement problem.
As outlined previously, the backspin produced by the drop punt kick, results in a Magnus force that provides the ball with greater hang time (vertical force). Conversely, figures 6 illustrates a ball travelling in a curvilinear path, as a result of a side Magnus force. This is because the ball has right-side spin, which creates high pressure to the left of the ball and low pressure to the right of the ball (direction of the goals) (McLester & Pierre, 2007). Figure 7 below, illustrates the same scenario when kicking from the other side of the goals.
As this Magnus force is created as a result of Newton's third law of motion (action-reaction), the amount of force applied to the ball and the position of the collision, will impact the magnitude and the direction of
the Magnus force (Blazevich, 2012). As a result, this kick is often difficult to master because the force from the foot segment must contact the ball at the correct position in order to produce the desired Magnus force. In order to manipulate the point of collision, the player displayed in figure 8 stands at a slight angle away from the target. However, the nose of the ball is facing down, pointing towards the intended target (goals). As this is a set shot, rule requirements state that a player must stay on the 'line of the mark', otherwise the umpire will call "play on". However, from a biomechanical perspective, the player would need to move off the 'line of the mark'. Therefore, the player would need to dispose of the ball quickly and efficiently. As a result of the biomechanical principles above, coaching cues should aim to incorporate the following when teaching a banana kick.
1) Face away from the target, with the nose of the ball pointing towards the target. WHY: to prepare to drop the ball from the correct angle.
2) Hold the ball between a 45-60 degree angle in front of the body, with the right hand forward on the ball (figure 7), while the left hand is placed further down the ball (closer to the nose of the ball). WHY: to prepare to drop the ball from the correct angle.
3) Drop the ball down so that it contacts the foot on the same angle. WHY: so the foot segment collides with the ball on the correct angle and with enough force to create side spin.
1) Face away from the target, with the nose of the ball pointing towards the target. WHY: to prepare to drop the ball from the correct angle.
2) Hold the ball between a 45-60 degree angle in front of the body, with the right hand forward on the ball (figure 7), while the left hand is placed further down the ball (closer to the nose of the ball). WHY: to prepare to drop the ball from the correct angle.
3) Drop the ball down so that it contacts the foot on the same angle. WHY: so the foot segment collides with the ball on the correct angle and with enough force to create side spin.
Based on this biomechanical analysis of a typical kicking pattern, as well as key principles associated with the drop punt, the torpedo kick, and the banana kick; physical educators and coaches can use this information to inform skills cues and practice conditions. This blog has provided suggestions as to where specialised kicks can be used within a 'real-game' situation. Drawing from a Dynamical Systems Theory, physical educators and coaches might choose to manipulate the task constraints of the game in order to create similar contexts, encouraging the execution and practice of these specialised kicks (Davids, Button, & Bennett, 2008). As the literature suggests (Davids, Button, & Bennett, 2008; Pinder, Renshaw, & Davids, 2009; Tan, Chow, & Davids, 2012), this would lead to strong information movement couplings consequently enhancing skilled performance.
Furthermore, the above suggested skill cues, have been established based on utilising certain biomechanical principles to solve particular movement problems. These skill cues, therefore, can help the physical educator to correct certain aspects of performance that are of high importance, rather than concentrating on minor ‘text-book-technique’ corrections. In addition, these skill cues can easily be transferred to other sports including Rugby League, Rugby Union, Soccer, and Gaelic Football.
Furthermore, the above suggested skill cues, have been established based on utilising certain biomechanical principles to solve particular movement problems. These skill cues, therefore, can help the physical educator to correct certain aspects of performance that are of high importance, rather than concentrating on minor ‘text-book-technique’ corrections. In addition, these skill cues can easily be transferred to other sports including Rugby League, Rugby Union, Soccer, and Gaelic Football.
References
Adelaide Football Club. (2011, April 5). The checkside punt with Walker & Smart [video file]. Retrieved from http://www.youtube.com/watch?v=G9Nij38xTWY#t=13
AFL Community. (2012, August 2). AFL Skills Guide - 3. Specialised Kicks [video file]. Retrieved from http://www.youtube.com/watch?v=APcqcMIhDzY
AFLVideos2011's channel. (2011, July 7). Best Torps in AFL History [video file]. Retrieved from http://www.youtube.com/watch?v=CTN54I3E5Us
Alam, F., Subic, A., Watkins, S., & Smits, A. J. (2009). Aerodynamics of an Australian rules foot ball and rugby ball. In M. Peters (Ed.) Computational Fluid Dynamics for Sport Simulation (pp. 103-127). Springer Berlin Heidelberg.
Aussierulesuk. (2008, December, 16). Skills - Torpedo Punt [video file]. Retrieved from http://www.youtube.com/watch?v=PGexCyiQ1To
Ball, K. (2008). Biomechanical considerations of distance kicking in Australian Rules football. Sports Biomechanics, 7(1), 10-23. doi:10.1080/14763140701683015
Blazevich, A. J. (2012). Sports biomechanics: the basics: optimising human performance. A&C Black.
Cross, R. (2010). Bounce of an oval shaped football. Sports Technology, 3(3), 168-180.
Davids, K., Button, C., & Bennett, S. (2008). Dynamics of skill acquisition: A constraints led approach. Human Kinetics.
Dichiera, A., Webster, K. E., Kuilboer, L., Morris, M. E., Bach, T. M., & Feller, J. A. (2006). Kinematic patterns associated with accuracy of the drop punt kick in Australian Football. Journal of Science and Medicine in Sport, 9(4), 292-298. doi:10.1016/j.jsams.2006.06.007
Fuss, F. K., Smith, R. M., & Leali, F. (2013). Kick precision and spin rate in drop and torpedo punts. Procedia Engineering, 60, 448-452. doi:10.1016/j.proeng.2013.07.011
Kellis, E., & Katis, A. (2007). Biomechanical characteristics and determinants of instep soccer kick. Journal of sports science & medicine, 6(2), 154.
McLester, J., & Pierre, P. S. (2007). Applied biomechanics: concepts and connections. Cengage Learning.
NAB AFL Auskick. (2012). Auskick Skills Guide. Retrieved from http://mm.afl.com.au/portals/0/afl_docs/development/coaching/junior_manual/AFL_Junior_Coaching_Manual_5.pdf
Orchard, J., Walt, S., & Garlick, D. (1999). Muscle activity during the drop punt. Journal of Sports Science, 17(10), 837-838.
Pedler, A. (2012). The biomechancis of the drop punt: three-dimensional kinematics, variability and muscle activity. Unpublished PhD thesis, University of South Australia - Adelaide.
Pinder, R. A., Renshaw, I., & Davids, K. (2009). Information–movement coupling in developing cricketers under changing ecological practice constraints. Human Movement Science, 28(4), 468-479. doi:10.1016/j.humov.2009.02.003
Rath, D. (2000, December). Biomechanics of Kicking Presentation. Australian Rules Coaching Course. Amsterdam, Netherlands.
Tan, C. W. K., Chow, J. Y., & Davids, K. (2012). ‘How does TGfU work?’: examining the relationship between learning design in TGfU and a nonlinear pedagogy. Physical Education and Sport Pedagogy, 17(4), 331-348. doi:10.1080/17408989.2011.582486
Young, W. B., & Rath, D. A. (2011). Enhancing foot velocity in football kicking: the role of strength training. The Journal of Strength & Conditioning Research,25(2), 561-566.
AFL Community. (2012, August 2). AFL Skills Guide - 3. Specialised Kicks [video file]. Retrieved from http://www.youtube.com/watch?v=APcqcMIhDzY
AFLVideos2011's channel. (2011, July 7). Best Torps in AFL History [video file]. Retrieved from http://www.youtube.com/watch?v=CTN54I3E5Us
Alam, F., Subic, A., Watkins, S., & Smits, A. J. (2009). Aerodynamics of an Australian rules foot ball and rugby ball. In M. Peters (Ed.) Computational Fluid Dynamics for Sport Simulation (pp. 103-127). Springer Berlin Heidelberg.
Aussierulesuk. (2008, December, 16). Skills - Torpedo Punt [video file]. Retrieved from http://www.youtube.com/watch?v=PGexCyiQ1To
Ball, K. (2008). Biomechanical considerations of distance kicking in Australian Rules football. Sports Biomechanics, 7(1), 10-23. doi:10.1080/14763140701683015
Blazevich, A. J. (2012). Sports biomechanics: the basics: optimising human performance. A&C Black.
Cross, R. (2010). Bounce of an oval shaped football. Sports Technology, 3(3), 168-180.
Davids, K., Button, C., & Bennett, S. (2008). Dynamics of skill acquisition: A constraints led approach. Human Kinetics.
Dichiera, A., Webster, K. E., Kuilboer, L., Morris, M. E., Bach, T. M., & Feller, J. A. (2006). Kinematic patterns associated with accuracy of the drop punt kick in Australian Football. Journal of Science and Medicine in Sport, 9(4), 292-298. doi:10.1016/j.jsams.2006.06.007
Fuss, F. K., Smith, R. M., & Leali, F. (2013). Kick precision and spin rate in drop and torpedo punts. Procedia Engineering, 60, 448-452. doi:10.1016/j.proeng.2013.07.011
Kellis, E., & Katis, A. (2007). Biomechanical characteristics and determinants of instep soccer kick. Journal of sports science & medicine, 6(2), 154.
McLester, J., & Pierre, P. S. (2007). Applied biomechanics: concepts and connections. Cengage Learning.
NAB AFL Auskick. (2012). Auskick Skills Guide. Retrieved from http://mm.afl.com.au/portals/0/afl_docs/development/coaching/junior_manual/AFL_Junior_Coaching_Manual_5.pdf
Orchard, J., Walt, S., & Garlick, D. (1999). Muscle activity during the drop punt. Journal of Sports Science, 17(10), 837-838.
Pedler, A. (2012). The biomechancis of the drop punt: three-dimensional kinematics, variability and muscle activity. Unpublished PhD thesis, University of South Australia - Adelaide.
Pinder, R. A., Renshaw, I., & Davids, K. (2009). Information–movement coupling in developing cricketers under changing ecological practice constraints. Human Movement Science, 28(4), 468-479. doi:10.1016/j.humov.2009.02.003
Rath, D. (2000, December). Biomechanics of Kicking Presentation. Australian Rules Coaching Course. Amsterdam, Netherlands.
Tan, C. W. K., Chow, J. Y., & Davids, K. (2012). ‘How does TGfU work?’: examining the relationship between learning design in TGfU and a nonlinear pedagogy. Physical Education and Sport Pedagogy, 17(4), 331-348. doi:10.1080/17408989.2011.582486
Young, W. B., & Rath, D. A. (2011). Enhancing foot velocity in football kicking: the role of strength training. The Journal of Strength & Conditioning Research,25(2), 561-566.