Measuring coordination and variability in coordination

This chapter reviews tools for measuring movement coordination and its variability and draws attention to the capacity of enhanced technology in motion analysis for providing detailed measurements of the coordination among limb segments and joints of the body. The review is highly relevant for theorists of motor control interested in measuring movement coordination and its variability during complex actions with multiple degrees of freedom such as locomotion. Key differences in methodological assumptions in the literature on biomechanics and motor control are identified, such as in assumptions regarding the definition of phase angle used when describing coordination between two segments. Decisions in measurement protocol, such as whether conventional linear statistics or circular statistical techniques should be used, can greatly influence the level of variability found in coordination. Although the literature is currently focusing a lot of attention on continuous relative phase and vector coding techniques, no single idea technique exists for measuring coordination and its variability over time. Consequently, researchers need to be aware of the strengths and limitations of existing methods and should state the rationale for using particular methodologies in their research studies to help readers interpret what amount of variability in the data is likely due to measurement errors and discrepancies. Measuring coordination and its variability is an issue that continues to challenge researchers in the movement sciences.