Kinematics of drop punt kicking in Australian rules football - comparison of skilled and less skilled kicking

The types of kick that are performed in the football codes fall into two broad categories: punt kick and place kick. One type of punt kick is the major means of ball movement in Australian Rules football – the drop punt kick.\ud Past studies have investigated the biomechanics of kicking. The pattern of segmental interaction during the kicking motion – known as the proximal to distal sequence (PDS) – is the most consistent finding that is reported in the biomechanics of kicking literature. In this sequence the proximal segment (thigh) initiates the forward swing of the kicking limb towards the ball and the forward rotation of the distal segment (shank) follows. PDS motions are also typified by a higher angular velocity of the distal segment (shank). Studies that have compared the difference between skilled and less skilled kickers in Australian Rules football have found that the difference in performance is the result of 1) the position of the shank at the end of the backswing is higher above horizontal (further in the clockwise direction) for the skilled than it is for the less skilled, 2) the maximum angular velocity of the thigh during the forward swing is greater for the skilled than it is for the less skilled and 3) the skilled kickers demonstrate greater mean maximum angular velocity of the shank at foot – ball contact. Apart from these findings there is inadequate information about the mechanical features of a skillful drop punt kick. The objective of this study was to quantify and compare the kinematics of skilled and less skilled kicking. A general profile of the drop punt kick and the reliability of the kinematic variables were also reported. The reliability study was conducted first. Six subjects were tested on two occasions to establish the reliability of the equipment and methods. Variables were deemed to be reliable if they demonstrated an ICC equal or greater than r = 0.80. Of the 95 variables that were analysed 42% had an ICC greater than r = 0.79 and 25% were classified as having questionable to moderate reliability because r = 0.50 – 0.79. Only reliable variables were used to compare the skilled and less skilled groups.\ud Six elite skilled kickers and six elite less skilled kickers were used in the main study. All subjects used were AFL players at the time of the data collection. Two-dimensional video footage was taken of each kick using a high speed camera (200Hz). The camera was positioned so that its line of sight was perpendicular to the sagittal plane of motion. The video footage of each trial was processed through the Peak Motus motion analysis system.\ud The start of the kicking motion was identified by the maximum cw angle of the thigh. The time of foot – ball contact was the end of the motion. There were two phases that were identified during this time; transition and forward swing. The duration of each was 50% of movement time. The results of the current study showed that the skilled kickers held the ankle in a more plantarflexed position than did the less skilled kickers (skilled 46.7 degrees, less skilled 39.21 degrees, r = 0.70, ES = – 1.06, p = .071) at the time of foot – ball contact. This result indicates that a common trait amongst skilled kickers is the presence of a taut instep at foot – ball contact. This is one trait of skilled kickers that is often referred to by skills coaches within the AFL.\ud The maximum angular velocity of the shank (1402 degrees/second) was higher than that of the thigh (805 degrees/second). The mean knee extension angle at foot – ball contact was 50 degrees and the maximum knee extension angle occurred after foot – ball contact (150% movement time). There was no difference between groups in the magnitude of the angles or angular velocities (p &gt 0.2). There was a difference in the time between the maximum angular velocity of the thigh and the maximum angular velocity of the shank (p &lt 0.05). From this result we suggested that skilled kickers are distinguished from less skilled kickers based on the timing of the critical events not the magnitude of critical events