Hodder, Ryan ORCID: 0000-0001-8847-5876 (2022) Investigation of key tactical variables impacting on elite netball performance. PhD thesis, Victoria University.

Abstract

The collective positioning and behaviours of elite netball players are an important concept to understand, as they relate to the tactical plans and overall performance of a team. However, this is currently an under-researched field in most indoor team sports owning to previous limitations in indoor tracking systems. Thus, this thesis investigated the use of collective tactical variables in elite netball matches and training, captured using a local positioning system (LPS). Collective tactical variables were used to explore collective movement and positioning behaviours in matches, examining the more successful movement patterns and how these varied in small sided games (SSGs), commonly used in training. Study 1 assessed the validity of the Catapult T6 LPS to measure inter-unit distance. Eight recreationally-active, female indoor team-sport players completed a circuit comprised of seven movements (walk, jog, jump, sprint, 45º change of direction and shuffle), on an indoor court. Participants wore a receiver tag (ClearSky T6, Catapult Sports) and seven reflective markers, allowing for comparison with the reference system (©Vicon Motion Systems, Oxford Metrics, UK). The criterion validity against the reference system resulted in a root mean square error of 0.20 ± 0.05 m. Additionally, analysis was conducted on five distance bands to assess the association between distance and inter-unit distance validity. The resulting mean bias presented an overestimation for the LPS in all distance bands, while the percentage of variance accounted for remained stable for all distance bands, excluding the > 20 m band. These results suggest the Catapult T6 LPS has acceptable accuracy - within 20 cm - for measuring inter-unit distance, as such opening up opportunities for further research into collective tactical variables for indoor team sports. Study 2 of this thesis used the validated ClearSky LPS to explore collective tactical variables during seven elite netball matches at the team and sub-group level. Collective tactical variables were explored during attacking and defending possessions and included; inter-player distance, width, length, surface area, centroids, width-per-length ratio and stretch indices. During attack, the team and all sub-groups adopted greater lateral dispersion between players, while on defence there was generally greater longitudinal dispersion. Additionally, greater irregularity (measure of predictability within time-series data) was observed in sub-groups most present and active in the play (forwards on attack, defenders on defence). Study 3 followed on from the results of the previous study, by modelling the effects of collective tactical variables and contextual predictors on scoring probability in elite netball. The effects were estimated via a logistic-regression version of the generalized linear mixed model, with adjustments for several predictor variables. Extremely short possessions were associated with decreased scoring probability, while lateral dispersion negatively affected the probability of scoring for both teams. These results indicated that, in general, it is more favourable to maintain positioning and ball movement in the middle of the court. Finally, Study 4 focused on SSGs, which are commonly used in training to replicate match outputs. The collective tactical variables of four attacking and four defending elite netball players were analysed to compare three SSG conditions: 4v4, 5v5 and 6v6. Two, 20-min SSGs for each condition were analysed using a linear mixed model. The irregularity of width-per-length ratio of the four attacking and four defending players was greatest in 4v4, the attackers’ inter-player distance and length variability was greatest in 5v5, while the four attacking players had the smallest mean surface area in 6v6. This thesis provides an exploration into the use of collective tactical variables in elite netball. As a combination of studies, this thesis is an important investigation into methods available for performance analysis research in netball and other indoor team sports. The key findings showing tactical analysis via collective tactical behaviours hold useful information for elite netball. Of interest, different patterns of positioning and movements exist between attacking and defending phases of play and sub-groups. All sub-groups displayed increases to their lateral dispersion during attack and active sub-groups presented greater irregularity, aligning with the positional dependencies and restrictions of netball. Also, certain collective tactical variable outputs are more successful than others, most prominent being shorter possession associated with decreased score probability, suggesting maintaining ball possession early is a key driver in score probability. Finally, in training SSGs differ tactically with different number of players included in the drills, with lower numbers causing defenders to exhibit greater irregularity while for greater numbers, players were closer to their teammates, both results displaying specific coaching principles that can be trained.

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