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

This protocol presents a novel approach for evaluating the coordination of the visual somata sensory and vestibular systems, and related muscle activation required to maintain postural stability. This technique can be used to perform a comprehensive investigation of the neuromuscular control for chronic ankle instability through the combination of computerized dynamic posturography, and related muscle activity. This method could also be used to explore postural stability and related muscle activity in other conditions such as neurologic or musculoskeletal system disorders.

Before beginning an analysis, turn on the CDP system and complete a self-calibration to confirm that the instrument is operating at a 100 Hertz sampling frequency. In the software, double-click Balance Manager System, Clinical Module, and New Patient. Input the participant name, height, ID, weight, and age, and select Assessment, Sensory Organization Test, Motor Control Test, Adaption Test, Limits of Stability, and Unilateral Stance.

Turn on the surface EMG system and double click the EMG motion tools icon. Specify the trigger signals and establish the participant ID.And place one wireless electrode onto the belly of each lower extremity muscle to be measured. Then use the synchronization line to connect the surface EMG system with the CDP system, and adjust the surface EMG system camera to capture the signal indicator light of the CDP system.

When both systems are ready, use a safety harness to fix the participant to the support bar, and carefully align the participant's bare feet with the force plates so that the participant is facing the visual surround. Then turn off the screen embedded in the visual surround. To conduct a sensory organization test, instruct the participant to stand upright with their center of gravity as stable as possible, and have the participant complete each test three times for 20 seconds per test under each condition as indicated in the table.

For a unilateral stance analysis, instruct the participant to place their hands on the anterior superior iliac spine with their eyes open and to consider the unstable ankle side as the support leg. Have the participant fully extend and bend the knee joint of their non supporting leg by approximately 30 degrees while standing stably for 10 seconds. After the third trial, have the participant repeat the same measurement with their eyes closed.

For a limit of stability test, instruct the participant to maintain their center of gravity in the central area until they hear a ring sound, at which point the participant should lean their body and quickly shift their center of gravity into the targeted frame in one of eight directions in the screen for 10 seconds. To conduct a motor control test, instruct the participant to restore their body stability in response to the unexpected slipping of the force plates. To perform an adaption test, instruct the participant to restore their body stability by directing the toes upward or downward in response to five consecutive unexpected rotations at a 20 degree per second velocity.

When all of the tests have been completed in the processing window of the surface EMG software import the CD3 file of the EMG raw data and MP4 file of the light video. In the processing pipeline operations, set the Butterworth filter with low pass to 450 Hertz and an order of two, the high pass to 20 Hertz with an order of two, the notch filter to 50 Hertz, and the root mean square smoothing window to 100 milliseconds. In the Generates Events tab, set all channels go above five X baseline noise standard deviations for at least 50 milliseconds to muscle on, and all channels drop below five X standard deviations over baseline for at least 50 milliseconds to muscle off.

Then in the Generate Parameters tab, select integral electromyography, root mean square, mean power frequency, medium frequency. In this analysis, as indicated by the green bars, the participant was able to better coordinate their three sensory systems and to more effectively respond than their age matched normative counterpoint in the dataset. Using their vision, proprioception, and vestibule sensory sensations to maintain balance throughout the sensory analysis.

The participant mainly relied on the ankle strategy and their ability to maintain postural stability. The total swing between the left and right legs was normal both when the participant's eyes were open and when they were closed. The participant exhibited a delayed reaction time between the sending of the move signal and the beginning of body movement, but a normal movement velocity.

For the forward and right end point excursions, the movement distance of the center of gravity did not reach the normal range. The maximum distance of the center of gravity movement was normal however. The participant demonstrated a normal weight distribution but an abnormal backward displacement response suggesting a unilateral orthopedic injury.

In addition, the increase in amplitude scaling was bipedaly symmetrical in relation to the amplitudes of the force plate slippage, and the sway energy score was normal. Be sure to accurately input the participant's age, height, and weight, and to correctly align the foot positions, as these parameters determine the location of the CDP and affect the postural analysis.