Change-of-Direction (COD) Biomechanics in Sport: A Systematic Review of the Possible Use of IMU

Abstract

Background/Objectives: Change-of-direction (COD) movements represent a fundamental component of performance in multidirectional sports and constitute one of the primary mechanisms of knee injury. The biomechanical assessment of such movements has traditionally relied on optoelectronic systems and force platforms, tools characterized by high accuracy but limited applicability in field settings. Inertial measurement units (IMUs) represent a promising alternative; however, operational doubts and uncertainties frequently persist. Therefore, the purpose of this systematic review was to critically evaluate the concurrent validity and practical utility of IMU sensors for detecting the biomechanical characteristics of COD maneuvers in sport. Methods: The bibliographic search was conducted in March 2024 across the PubMed MEDLINE, Scopus, and Web of Science databases, using Boolean combinations of the following keywords: IMU, “inertial measurement unit”, CoD, “change of direction”, “cutting maneuvers”, sport, and soccer. Study selection and analysis were performed, and methodological quality was assessed using the QUADAS-2 tool. Results: In the original search (March 2024), ten studies were included, involving 208 participants; a formal update of the search (through August 2026), conducted with the same protocol, identified two additional candidate studies (14 and 30 participants), bringing the total to twelve studies and 252 participants; both supplementary studies underwent the same four-reviewer independent screening, full-text data extraction and QUADAS-2 appraisal applied to the original ten studies. The findings indicate that IMUs demonstrate good concurrent validity for kinematic variables in the sagittal plane, particularly at the hip and knee joints, with ICC values up to 0.99 and a mean RMSE below 2°. Performance decreases substantially in the frontal and transverse planes. Regarding ground reaction forces, IMUs provide acceptable estimates of mean values, but not of instantaneous forces. For temporal variables, IMUs proved comparable to timing gates in the assessment of explosive actions. Conclusions: Based on a limited and heterogeneous evidence base of twelve studies, IMUs appear to be a promising and accessible technology for specific field-based applications, particularly for the assessment of CODs at 0°, 45°, and 90° in the sagittal plane, for monitoring right-left asymmetries, and for counting explosive actions. Given the small number of included studies and their methodological heterogeneity, these findings should be interpreted with caution. IMUs cannot yet be recommended as a complete replacement for gold-standard systems in applications requiring high precision or detailed analysis of instantaneous forces.