Design and validation of an observational instrument for defence in soccer based on the Dynamical Systems Theory

Abstract

The research about soccer defensive phase shows many limitations regarding the procedures and operational definitions. The aims of this paper are to create an observational instrument based on Dynamic Systems concepts and evidence sufficient content validity to adequately and reliably recode defensive soccer behaviours. For these, a five-stage development process for validity was followed: (1) an initial literature review, instrument development, observation training; (2) adapting an existing systematic observational instrument; (3) pilot study with non-experts; (4) content validity with experts (coaches and researchers) and (5) inter- and intra-observer reliability. Using Aiken’s V coefficient and its cut-off value to determine validity content, consensus was found ( V > 0.67, n = 32, p < 0.05) for all items answered by participants in pilot study and for almost all subjects in the experts’ study ( V > 0.69, n = 12, p < 0.05). Also, Cohen’s Kappa shows inter- and intra-reliability values of 0.87 and 0.90, respectively. The final model, entitled Theoretical Dynamic Model of Soccer Defence, and the observational instrument, named Soccer-Defence, with 14 criteria and category systems, and 106 categories, seems to be suitable for analysing the defensive process in soccer and could be used to find strengths or weaknesses of tactical–technical defensive patterns of play and to help coaches to better prepare their teams.