Influence of age on postural control during dual task: a centre of pressure motion and electromyographic analysis

Background: Dual task influences postural control. A cognitive task seems to reduce muscle excitation during a postural balance, especially in older adults (OA). Aim: The aim of this study is to evaluate the effect of three cognitive tasks on muscle excitation and static postural control in OA and young adults (YA) in an upright posture maintenance task. Methods: 31 YA and 30 OA were evaluated while performing a modified Romberg Test in five different conditions over a force plate: open eyes, closed eyes, spatial-memory brooks’ test, counting backwards aloud test and mental arithmetic task. The surface electromyographic signals of Tibialis anterior (TA), Lateral Gastrocnemius (GL), Peroneus Longus (PL), and Erector Spinae (ES) was acquired with an 8-channel surface electromyographic system. The following variables were computed for both the electromyographic analysis and the posturographic assessment: Root mean square (RMS), centre of pressure (CoP) excursion (Path) and velocity, sway area, RMS of the CoP Path and 50%, 95% of the power frequency. Mixed ANOVA was used to detect differences with group membership as factor between and type of task as within. The analysis was performed on the differences between each condition from OE. Results: An interaction effect was found for Log (logarithmic) Sway Area. A main effect for task emerged on all posturographic variables except Log 95% frequencies and for Log PL and ES RMS. A main effect for group was never detected. Discussion and conclusion: This study indicates a facilitating effect of mental secondary task on posturographic variables. Non-silent secondary task causes increase in ES and TA muscle activation and a worsening in static postural control performance.