Adrien M. Buttram1, Stephanie Gibson1, Joel Hager1, Karlie Abernathy1, José Canelon1, Benjamin Thomas1, Damon Knighton1, Daniele Piscitelli2, Stanislaw Solnik1. 1University of North Georgia, Dahlonega, GA. 2University of Connecticut, Mansfield, CT.

BACKGROUND: The central nervous system organizes motor elements (e.g. muscles, joints, fingers) into task-specific synergies to stabilize motor task performance. The Uncontrolled Manifold (UCM) hypothesis quantifies synergies using analysis of covariation between motor elements. Recently, the UCM has been proposed as a biomarker of movement quality to investigate sensorimotor impairments. However, methodological limitations, including unknown measurement properties, hinder the practical application of UCM in clinical practice. This study aimed to investigate the reliability (i.e., test-rest and measurement error) of UCM parameters in healthy young adults. METHODS: 15 subjects (24.8 ± 1.2 yrs old) used both hands index and middle fingers to press on four force sensors. At four experimental sessions separated by 1 hour, one day, and one week, subjects performed three 2-minute trials of cyclic total force production at 20% of maximal voluntary contraction (MVC). Each trial consisted of 2-second force production separated by 2-seconds rest intervals, with visual feedback on the target force. We computed the synergy index (ΔV) for all testing sessions to quantify between-hand synergies stabilizing the target force. We averaged ΔV values from trials within each session. We investigated the test-retest reliability of ΔV with the Intraclass Correlation Coefficient (ICC3,k) with 95% confidence intervals (95% CI). Standard Error of Measurement (SEM) and Minimal Detectable Change (MDC) were determined. RESULTS: The mean number of force cycles was 29 in all testing sessions. The average ΔV for all subjects across all sessions was 0.87±0.29. The test-retest reliability reported an ICC3,k = 0.88 (95%CI: 0.72, 0.95; F(14,42)=7.91, p<0.001), with SEM = 0.10, and MDC = 0.28. CONCLUSIONS: The test-retest reliability was excellent, with a value close to acceptable for clinical measures (i.e., ICC > 0.9). The findings show that ΔV values were consistent across 1-hour, 1-day, and 1-week testing sessions. Our study supports using UCM-based biomarkers of movement quality in healthy young adults. Our results may advance the incorporation of UCM into clinical assessment of movement quality and for tracking recovery over time. This will help bridge neuroscience with the study of movement quality for a variety of populations and impairments.

This document is currently not available here.