Evaluating Postural Control and Lower-extremity Muscle Activation in Individuals with Chronic Ankle Instability

Summary

Individuals with chronic ankle instability (CAI) exhibit postural control deficiency and delayed muscle activation of lower extremities. Computerized dynamic posturography combined with surface electromyography provides insights into the coordination of the visual, somatosensory, and vestibular systems with muscle activation regulation to maintain postural stability in individuals with CAI.

Abstract

Computerized dynamic posturography (CDP) is an objective technique for the evaluation of postural stability under static and dynamic conditions and perturbation. CDP is based on the inverted pendulum model that traces the interrelationship between the center of pressure and the center of gravity. CDP can be used to analyze the proportions of vision, proprioception, and vestibular sensation to maintain postural stability. The following characters define chronic ankle instability (CAI): persistent ankle pain, swelling, the feeling of “giving way,” and self-reported disability. Postural stability and fibular muscle activation level in individuals with CAI decreased due to lateral ankle ligament complex injuries. Few studies have used CDP to explore the postural stability of individuals with CAI. Studies that investigate postural stability and related muscle activation by using synchronized CDP with surface electromyography are lacking. This CDP protocol includes a sensory organization test (SOT), a motor control test (MCT), and an adaption test (ADT), as well as tests that measure unilateral stance (US) and limit of stability (LOS). The surface electromyography system is synchronized with CDP to collect data on lower limb muscle activation during measurement. This protocol presents a novel approach for evaluating the coordination of the visual, somatosensory, and vestibular systems and related muscle activation to maintain postural stability. Moreover, it provides new insights into the neuromuscular control of individuals with CAI when coping with real complex environments.

Introduction

Computerized dynamic posturography (CDP) is an objective technique for the evaluation of postural stability under static and dynamic conditions and perturbation. CDP is based on the inverted pendulum model that traces the interrelationship between the center of pressure (COP) and the center of gravity (COG). COG is the vertical projection of the center of mass (COM), whereas COM is the point equivalent of the total body mass in the global reference system. COP is the point location of the vertical ground reaction force vector. It represents a weighted average of all the pressures over the surface of the contact area with the ground¹. Postural s....

Access restricted. Please log in or start a trial to view this content.

Protocol

Prior to tests, the participants signed an informed consent after receiving information about the experimental process. This experiment has been approved by the ethics committee of Shanghai University of Sports.

1. Equipment setup

1. Turn on the CDP system, complete self-calibration, and ensure that the instrument operates normally at 100 Hz sampling frequency.
   NOTE: Each of the two installed independent force plates measures three forces (Fx, Fy, and Fz) and three moments (Mx, My, and Mz). The x-axis is in the left–right direction and is perpendicular to the sagittal plane. The y-axis is in the forward–backward direction and is perp....

Access restricted. Please log in or start a trial to view this content.

Results

Representative CDP Results
Sensory organization test
The system evaluates the participant’s ability to maintain COG in the predetermined target area, when the environment changes as the peripheral signal input. Equilibrium score (ES) is the score under conditions 1–6 that reflects the ability to coordinate the sensory system to maintain postural stability (Equation 6). The composite score (COMP) is the weighted average score of al.......

Access restricted. Please log in or start a trial to view this content.

Discussion

The presented protocol is used to measure dynamic postural control and related muscle activity in individuals with CAI by synchronizing CDP with sEMG. CDP traces the trajectory of the COP and COG and provides insight into the interaction between sensory information (visual, somatosensory, and vestibular sensation) input and the external environment^8,21,22. It is an effective tool for the diagnosis of the functional activity limi.......

Access restricted. Please log in or start a trial to view this content.

Materials

Name	Company	Catalog Number	Comments
NeuroCom Balance Manager SMART EquiTest	Natus Medical Incorporated, USA		Its major components include: NeuroCom Balance Manager Software Suite, dynamic dual force plate (rotate & translate), moveable visual surround with 15” LCD display (it could provide a real time display of the subject’s center of gravity shown as a cursor during the task) and illumination, overhead support bar with patient harness, computer and other parts.
wireless Myon 320 sEMG system	Myon AG		The system consists of 16 parallel channels of transmitter signals, receiver, "EMG motion Tools" and "ProEMG" software,computer and other parts.