Postural Control and Ankle Muscle Stiffness During Continuous Cognitive Tasks and External Focus of Attention

• Main Author: Saunders, Deanna
• Other Authors: Lajoie, Yves
• Language: en
• Published: Université d'Ottawa / University of Ottawa 2017
• Subjects: Dual-task; Cognitive task; Postural control; Ankle stiffening; Attentional focus
• Online Access: http://hdl.handle.net/10393/36382; http://dx.doi.org/10.20381/ruor-20662

The objective of the present study was to; 1) determine if the use of a continuous cognitive task demonstrates distinct characteristics of a more automatic control of posture, compared to an external focus (EF) and feet together (FT) postural task, and to 2) examine which condition, if any, exhibits the characteristics of increased ankle stiffness proposed by Winter et al. (1998), as well as displaying increased ankle muscular co-contractions, which are a suggested neuromuscular mechanism that stiffens posture. Fifteen young adults stood on a force platform and performed 4 separate conditions: FT, EF, single number sequence (SNS), and double number sequence (DNS). Throughout the session, surface electromyography (EMG) signals were collected from the tibialis anterior (TA) and medial gastrocnemius (MG) of each leg. Each testing session consisted of 24 trials, with 6 per condition. Results displayed decreased sway area for SNS and DNS compared to FT. Sway variability in the anterior/posterior (AP) direction SNS and DNS were smaller compared to EF and FT. As well sway variability in the medial/lateral (ML) direction was smaller for SNS and DNS compared to FT. ML Mean velocity (MV) did not differ across conditions, though in the AP direction it was larger for SNS and DNS compared to EF and FT. AP Mean power frequency (MPF) was larger for SNS compared to FT. In the ML direction MPF was larger for SNS and DNS compared to FT. Co-Contraction indices revealed no differences across conditions. Conversely the left TA for DNS revealed increased EMG activation compared to EF and SNS.