JcvPCA and JsvCRP : a set of metrics to evaluate changes in joint coordination strategies

TL;DR

This paper introduces two novel metrics, JcvPCA and JsvCRP, to better analyze and differentiate changes in inter-joint coordination strategies during movement, addressing limitations of existing methods.

Contribution

The paper presents two new metrics for evaluating inter-joint coordination, improving the understanding of temporal and spatial changes in joint contributions and synchronization.

Findings

Metrics successfully differentiate coordination strategies

Application to simulated and experimental data validates effectiveness

Potential for clinical and ergonomic applications

Abstract

Characterizing changes in inter-joint coordination presents significant challenges, as it necessitates the examination of relationships between multiple degrees of freedom during movements and their temporal evolution. Existing metrics are inadequate in providing physiologically coherent results that document both the temporal and spatial aspects of inter-joint coordination. In this article, we introduce two novel metrics to enhance the analysis of inter-joint coordination. The first metric, Joint Contribution Variation based on Principal Component Analysis (JcvPCA), evaluates the variation in each joint's contribution during series of movements. The second metric, Joint Synchronization Variation based on Continuous Relative Phase (JsvCRP), measures the variation in temporal synchronization among joints between two movement datasets. We begin by presenting each metric and explaining their derivation. We then demonstrate the application of these metrics using simulated and experimental datasets involving identical movement tasks performed with distinct coordination strategies. The results show that these metrics can successfully differentiate between unique coordination strategies, providing meaningful insights into joint collaboration during movement. These metrics hold significant potential for fields such as ergonomics and clinical rehabilitation, where a precise understanding of the evolution of inter-joint coordination strategies is crucial. Potential applications include evaluating the effects of upper limb exoskeletons in industrial settings or monitoring the progress of patients undergoing neurological rehabilitation.