Effects of dual-task conditions on cervical spine movement variability.

BACKGROUND The potential to accurately perform cervical movements during more challenging tasks might be of importance to prevent dysfunctional motion characteristics. Although sensorimotor function during dual-task conditions are of increasing interest in biomedical and rehabilitation research, effects of such conditions on movement consistency of the neck have not yet been investigated. OBJECTIVE In this crossover MiSpEx(Medicine in Spine Exercise)-diagnostic study, we aimed to explore differences between single and dual-task conditions on cervical movement variability. METHODS Nineteen healthy participants (9 male; 24.5 ± 3.3 y) performed 10 repetitive maximal cervical movements in (1) flexion/extension and (2) lateral flexion, during one single- and during two dual-task test conditions (cognitive, motor) in a randomised and cross-over sequence. Latter consisted of a working memory n-back task (n= 2) and a repetitive ankle movement task. Range of motion (RoM) was assessed using an external three-dimensional ultrasonic movement analysis system. Coefficient of variation (CV) for repetitive RoM was analysed for differences between conditions and controlled for variances in intra-individual movement characteristics. RESULTS Friedman and post-hoc Bonferroni-adjusted confidence intervals for differences from single- to dual-task values revealed changes in CV in flexion/extension from single-task to motor dual-task (+0.02 ± 0.02 (97.5%CI: 0.01; 0.03); p< 0.05) but not to cognitive dual-task condition (+0.01 ± 0.02 (97.5%CI: 0.003; 0.02)) nor for lateral flexion (p> 0.05). Pearson regression analyses revealed a linear negative (p< 0.01) influence of CV in flexion/extension on differences from single to both cognitive (R=2 0.47) and motor dual-task (R=2 0.55). Results for lateral flexion are comparable, baseline CV negatively impacts differences to cognitive (R=2 0.2) and motor dual-task performance (R=2 0.76; p< 0.01). CONCLUSIONS Participants with comparable low cervical CV at single-task display a profound increase during dual-task conditions while participants with a higher variability remained almost stable or showed a decrease. The results point toward a complex interrelationship of motion patterns and adaptation processes during challenging tasks in respect of cervical CV.