Prediction of soccer penalty kick direction from single-joint kinematics using the Echo State Network

Abstract

Anticipating soccer penalty kick direction is crucial for goalkeepers because reaction time alone is often insufficient after ball contact. This study examines whether kick direction (right vs. left) can be predicted from pre-impact kinematics estimated by markerless pose tracking. Four participants performed left- and right-targeted penalty kicks, and 2D coordinates of 25 joints were extracted using OpenPose. Echo State Networks (ESNs) were trained in a joint-wise manner using single-joint coordinate time series, with a ridge-regression readout. High prediction performance as achieved under kicker-specific conditions, whereas cross-subject generalization was limited. A decision-basis analysis using the decision-axis projected update (DAPU) further revealed time intervals that consistently contributed to decision formation.