Exploration of collective tactical variables in elite netball: An analysis of team and sub-group positioning behaviours

Collective tactical behaviours are aspects of player interactions that are particularly important in netball, due to its unique restrictions on player movement (players unable to move when in possession of the ball and positional spatial restrictions). The aim of this study was to explore variables representing collective tactical behaviours in netball. A local positioning system provided player positions of one team throughout seven elite-level netball matches. The positions were analysed to provide mean, variability (standard deviation) and irregularity (normalised approximate entropy) for each attack and defence possession (470 and 423, respectively) for the team and positional subgroups (forwards, midcourts and defenders) for 10 position-related variables. Correlational analyses showed collective tactical variables could be grouped as lateral and longitudinal dispersion variables. The variables were each analysed after log transformation with a linear mixed model to compare attack and defence and to estimate standardised effects on attack and defence of possession outcome, possession duration, score difference, match time, opposition strength and season time. During attack, the team and all sub-groups adopted greater lateral dispersion between players, while on defence there was generally greater longitudinal dispersion. The team also showed increased longitudinal dispersion when home and opposition possessions ended in a score. Additionally, greater irregularity was observed in active sub-groups (forwards on attack, defenders on defence). Score difference and opposition strength had trivial-small but generally unclear effects. In conclusion, these effects show that analysis of player positions on attack and defence is a promising avenue for coaches and analysts to modify collective tactical behaviours in netball.

Criterion Validity of Catapult ClearSky T6 Local Positioning System for Measuring Inter-Unit Distance

The validity of a local positioning system (LPS) to measure inter-unit distance was investigated during a team sport movement circuit. Eight recreationally active, female indoor team-sport players completed a circuit, comprising seven types of movements (walk, jog, jump, sprint, 45° change of direction and shuffle), on an indoor court. Participants wore a receiver tag (ClearSky T6, Catapult Sports) and seven reflective markers, to allow for a comparison with the reference system (©Vicon Motion Systems, Oxford Metrics, UK). Inter-unit distance was collected for each combination of participants. Validity was assessed via root mean square error, mean bias and percentage of variance accounted for, both as an overall dataset and split into distance bands. The results presented a mean root mean square error of 0.20 ± 0.05 m, and mean bias detected an overestimation for all distance bands. The LPS shows acceptable accuracy for measuring inter-unit distance, opening up opportunities to utilise player tracking for tactical variables indoors.

The pharmacokinetics of sodium cromoglycate in man after intravenous and inhalation administration

The pharmacokinetics of sodium cromoglycate in four healthy volunteers after slow intravenous infusion have been evaluated following measurement of plasma concentrations by radioimmunoassay. The results confirm earlier findings that sodium cromoglycate is rapidly eliminated from the body and that the data can be fitted to a two compartment open model. The pharmacokinetic parameters derived from the intravenous administration were used to evaluate the pharmacokinetics after inhalation administration via the Spinhaler. A model for absorption from the lungs is described which involves absorption at two different rates; this gives a better fit to the observed data than a single absorption rate. A fast absorption rate constant with a mean value of 0.54 min-1 and a slower rate constant with a mean value of 0.0097 min-1 were found. Of a mean total of 2.84 mg absorbed from a 20 mg inhaled dose, 0.68 +/- 0.15 (s.e. mean) mg were absorbed at the fast rate and 2.17 +/- 0.37 mg at the slower rate. These rates probably reflect absorption from different sites within the lungs. The results may have important implications for interpretation of clinical findings.