Tuesday, March 27, 2012

Get it through the sticks - thinking about goal kicking performance in Australian football

Get it through the sticks - thinking about goal kicking performance in Australian football
The footy season has started and goal-kicking has been on mind. Specifically, the factors that affect goal kicking performance and the implications they have on the preparation of players for this task. This is not a straight forward reflection as goal kicking can be from a 'set shot' resulting from a mark or free kick, or from a kick resulting from the dynamics of play as it unfolds - a quick 'snap' at goals, a kick on the run, a kick forced onto the non prefered leg due to defence action or defence pressure restricting time to position onto a preferred kicking leg.
With this dynamic in mind I embarked upon research to find what was 'out there' that could inform my understanding of goal kicking and influence my coaching of this part of the game. What I found is that there is actually 'not much out there'. However, I'll begin with what I did find before looking at research from some other sports to see what that might reveal to assist coaching development of goal kicking.

The biomechanics of kicking
As a phys ed teacher I am well aware that biomechanics affects performance efficiency. To consider the mechanics of kicking in Australian football I looked at the work of Kevin Ball. He has researched the biomechanical aspects of kicking and set shot accuracy in AFL football and found the following technical factors influence set-shot accuracy:
- the approach line (the least accurate kicks in the study had a curved approach that did not conclude in a straight line before the kick)
- ball movement during the approach (should be minimised)
- ball position at drop (drop the ball in line with the kicking thigh)
- ball contact
- follow through position (leg should point towards the goals)
While comparing the kicking mechanics of elite juniors (U18) to one of the more consistent set shot kicks of recent times, Matthew Llyod, Ball found that Llyod was more upright, guided the ball down further and released the ball closer to the ground than most of the U18 players. He also found that Llyod maintained his vision through the goals while approaching his kick - he did not look toward the ground or at the player guarding the mark which U18 players were prone to.
Coaches need to pay attention to the mechanics of players set shot kicks during practice and to the visual display of the players as they approach the kick

Fatigue, Concious Control and Perception
Ball also found that in a relatively'self paced' skill like a set shot at goals, fatigue and an attempt to consciously control the kick can lead to changes in technique that are detrimental to performance.
Although NFL field goal kicking was the context, Witt & Dorsch (2009) found that kickers who made more successful kicks perceived the goals to be further apart, while the more kicks that are missed the narrower the goals were perceived
Coaches should assist players develop a routine that provides time to lower heart rate and 'calm the mind' so the set shot routine becomes more 'instinctive' rather than robotic

Asymmetrics
Nicholls, Loetscher & Rademacher (2010) reviewed AFL goal kicking data from the 2005-2009 seasons to consider whether one side of the goals was favoured when a point was scored rather than a goal. They found more right points than left points were scored (left or right were considered from the kickers perspective), and that there was a clear interaction between the side the kick was taken and side of the 'miss' (a point scored instead of a goal). That is, kicks from the right side were more likely to result in right 'point' scored, and vic-versa for the left. I think we would expect that, but what I found most interesting was that the research found that when players aimed for the mid-point between the goal posts there was a bias toward a right deviation with the kick. Right foot players may shift their spatial attention to the right when estimating the mid-point of the goals in 'far space'.
Perhaps coaches need to consider where they tell players to 'aim' when kicking as it may not be quite as simple as telling players to 'kick it through the middle'

Angles of Opportunity
Galbraith & Lockwood (2010) performed a mathematical deconstruction of two parameters that affect set shot difficulty - angle and distance. While the goal-width (post-to-post) is 6.4m, they found that the available goal width changes with distance and angle. No surpises there, but while the central corridor from goal-to-goal is the most favoured place to be when kicking for goal they suggest the mathematics points to this perception being an illusion as mathematically there are may positions, some at quite a substantial angle, which afford better opportunities (The key variable being distance from goals. For example, a kick from directly in front of goals/90degrees from a distance of 50m provides only a 7degree angle of oportunity - the same as a kick from 30m at 45degrees).
Gallbraith & Lockwood suggest creating 'circles of oportunity' using markers to create specific target locations with respect to distance and angle for set shot goal kicking....all points on a given circle define the same goal angle and so are points of equal opportunity for a successful kick. By putting this idea into practice in forward entry play-practices and goal kicking drills coaches open up goal kicking spaces more expansively and are not restricted to a 'hot-spot' directly in front of goal - making it harder for oposition defenses to get organised.

Unfortunately, I couldn't find any research pertaining specifically to goal kicking performance in Australian football emerging from the dynamics of play. I therefore looked for research from other invasion sports that provided ideas I could take into my Australian football coaching. The emerging constraints-led skill learning perspective from a consideration of a sport as a dynamic 'non-linear' system provided interesting reading. In summary, Davids et al (2004) considered soccer as a dynamic system and observed that movement decisions are made in response to position, movement and speed of team-mate's and opponents - order and disorder can emerge from play at any moment. Chow et al (2009) argued that practice activities that are representative of performance demands lead to more likely transfer of skills between practice and performance environments. Button et al (2003) looked at basketball shooting and concluded movement solutions need to be developed under realsitic task constraints. Wende (2005) investigated water-polo shot outcomes and found the removal of a defender and goalkeeper in practice results in changes in the relative coordination and timing of the shot, so shot practice needs to replicate defensive game pressure.
Coaches need to replicate the potential movement solutions that occur in a game during practice in order to rehearse optimal team and individual movement responses - goal kicking should be practiced under variable defensive pressure similar to what can be expected in game situations

Although the research literature on Australian football goal kicking is sparse, this review of literature has provided 5 clear directions for me to pursue in future planning of goal kicking practice. I hope readers may also find it useful.

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