Assessing rugby place kick performance from initial ball flight kinematics: development, validation and application of a new measure

Abstract

The appropriate determination of performance outcome is critical when appraising a performer's technique. Previous studies of rugby place kicking technique have typically assessed performance based on ball velocity, but this is not the sole requirement. Therefore, a mathematical model of rugby place kick ball flight was developed to yield a single measure more representative of true performance. The model, which requires only initial ball flight kinematics, was calibrated and validated using empirical place kick data, and found to predict ball position with a mean error of 4.0% after 22 m of ball flight. The model was then applied to the performances of 33 place kickers. The predicted maximum distance, a single performance measure which accounted for initial ball velocity magnitude and direction, and spin, was determined using the model and was compared against ball velocity magnitude. A moderate association in the rank-order of the kicks between these two measures (ρ = 0.52) revealed that the relative success of the kicks would be assessed differently with each measure. The developed model provides a representative measure of place kick performance that is understandable for coaches, and can be used to predict changes in performance outcome under different ball launch or environmental conditions.

The approach towards the ball, rather than the physical characteristics of the kicker, limits accurate rugby place kicking range

“…Those studies which did employ explosive tests, such as maximal jumps, tended to identify stronger correlations but may also have been impacted by the varied experience of the participants and the lack of familiarisation provided. In addition to kicking foot velocity magnitude, it is also important to consider the direction of the foot velocity vector given the importance of an appropriate ball trajectory in rugby place kicking (Atack et al, 2019a). We found the lateral direction of the kicking foot velocity vector in the horizontal plane at BC was strongly correlated with maximum distance (r = 0.69, p = 0.002).…”

“…Although the magnitude and direction of the kicking foot velocity and the magnitude of ball velocity are associated with rugby place kick performance, these alone do not determine overall place kick success (Atack et al, 2019a). Therefore, to complete our understanding it is vital to consider the factors that contribute to true place kick performance outcome, namely maximum distance.…”

“…To determine the performance of each kick, an aerodynamic model of rugby ball flight was used to obtain the predicted maximum distance (Atack et al, 2019a) using the measured initial ball kinematics. The trial in which the participant achieved the greatest predicted maximum distance was used for subsequent analysis.…”

Kicking foot swing planes and support leg kinematics in rugby place kicking: Differences between accurate and inaccurate kickers

“…To analyse each kicker's kinematics, all marker coordinates from the corresponding trial were firstly expressed relative to the position of the ball centre when resting on the tee, and global x-axis co-ordinates for left-footed kickers were inverted. The kicking foot centre of mass (CM) location was determined (Winter, 2005) and its raw trajectory was resampled at equal (0.01 m) spatial intervals (Willmott & Dapena, 2012) using an interpolating cubic Atack et al, 2018)) yielded the threshold limits of 33.3 and 30.7 m. The accurate group contains only kicks with a predicted maximum successful distance ≥ 33.3 m. The inaccurate group contains only kicks with a predicted maximum successful distance ≤ 30.7 m because they would have missed to the left of the posts from any greater distance. Of the remaining kicks, two were removed because they lay within the threshold limits (i.e.…”

Interval Kicking Program for the Punting and Place-Kicking Athlete: A Systematic Literature Review and Need Analysis

“…This kick is a method of scoring by either field goal or the point after touchdown in American football and is responsible for 45% of points scored in rugby union [ 37 , 44 ]. In comparison to punting, place-kicking precision and accuracy are more important as it is used in a scoring capacity wherein the ball must pass between two uprights and above a crossbar [ 45 ]. The mechanics of the kicking leg during a place kick can be broken into two phases, the late approach phase and the kicking phase.…”