Quantifying soccer penalty kick technique using wearable sensor data: a principal component analysis-based evaluation of whole-body movement changes due to shot placement

Abstract

A player’s kicking technique strongly influences penalty-kick outcomes, such as shot placement accuracy, yet it remains challenging to quantify holistically. Traditional analyses often focus on isolated biomechanical variables, which may not capture the integrated nature of whole-body movement or translate well into practical coaching. This study introduces an IMU-based principal component analysis (PCA) framework to quantify practice-oriented movement patterns in penalty kicks. The objectives were (1) to develop and validate interpretable “technique components” that represent practically executable movement strategies and (2) to apply them to examine how kicking technique varies practically with shot placement. Sixteen male amateur soccer players completed two tasks: (1) penalty kicks using deliberately exaggerated technique variations and (2) uninstructed self-selected kicks aimed at predefined goal zones. Whole-body kinematics (3D segment positions) were recorded with an Xsens IMU system. PCA was applied to time-normalized, mass-weighted segment positions centered to each participant’s baseline kick of the instructed technique extremes, yielding distinct and practically interpretable technique components. These represented continuous scales between opposing extreme strategies and were statistically validated using statistical parametric mapping (SPM). Valid components captured horizontal, vertical and lateral body movement, upper-body rotation, leg-swing strategy, sagittal and frontal arm swing, and head orientation. Subsequently, projecting the uninstructed kicks onto these components revealed systematic technique differences associated with shot placement (SPM rmANOVA). Shots to upper goal zones were characterized by a lower vertical body position and a stronger lateral lean toward the standing leg. By applying PCA to purposefully demonstrated technique variations, this study provides an objective framework for quantifying complex whole-body movement patterns in penalty kicks. The approach yields continuous, interpretable measures aligned with coaching terminology and can be applied to evaluate and monitor technique in practical settings. It offers a promising basis for data-driven feedback and future real-time training applications.