Effects of Dual-Task Conditions on Cervical Spine Movement Variability

Abstract

Although sensorimotor function and motor output during dual-task conditions are of increasing interest in biomedical research, effects of such conditions on movement consistency have not yet been investigated. PURPOSE: To further explore the effects of simple motor tasks’ adaptations on cervical movement variability. METHODS: Nineteen healthy subjects (9 male; 24.5±3.3 yrs) performed 10 repetitive maximal cervical movements in an upright sitting position at self-determined velocity. Motion characteristics in (1) flexion/extension and (2) lateral flexion were assessed during one single- and two dual-task test conditions (cognitive, motor). Latter consisted of a working memory n-back task (n = 2) and a repetitive ankle movement task. Tasks were performed in a randomized and cross-over sequence. Coefficient of variation as the primary outcome was calculated from raw 3D ultrasonic data. Data were statistically analyzed for differences between conditions and controlled for variances in intra-individual movement characteristics. RESULTS: Friedman and post-hoc Bonferroni-adjusted confidence intervals for the differences from single to dual-task values revealed significant changes in movement variability in flexion/extension for motor (+.02±.02 (97.5% CI: .01; .03); p= .01) but not for cognitive dual-task condition (+.01±.02 (97.5% CI: .003; .02)) nor for lateral flexion tasks (p> .05). Pearson regression analyses revealed a significant negative (p< .01) influence of coefficient of variation in flexion/extension on differences from single to both cognitive (R2= .47) and motor dual-task (R2= .55). Results for lateral flexion are comparable, baseline movement variability negatively impacts differences to cognitive (R2= .2) and motor dual-task performance (R2=.76; p< .01). CONCLUSIONS: Subjects with comparable low cervical movement variability at single-task display a profound increase of this variability during dual-task conditions while participants with a higher initial variability remained almost stable or showed a decrease. The results point toward a complex interrelationship of simple motion patterns and adaptation processes during more challenging tasks in respect of cervical motor variability. These findings might have impact for the development of motor learning processes and the detection of musculoskeletal malfunctions.