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Osouli Odlu H, Moradi H. Auditory Stimulus on Anticipatory Postural Adjustments in Patients with Multiple Sclerosis. MEJDS. 2020; 10 :54-54
URL: http://jdisabilstud.org/article-1-1251-en.html
1- University of Tehran
Abstract:   (1132 Views)
Background & Objective: Impaired balance and gait pattern are a major features of multiple scle¬rosis (MS) disease. Studies of postural adjustments in patients with MS have shown decreased magnitude and increased latency of muscle activations in anticipatory postural adjustments (APAs) during voluntary load release tasks and also in response to external perturbations (i.e. pendulum impact). Upright posture is an essential feature of human beings that enables functional activities and movements, but is known to be inherently unstable as center of mass of the body is located high with the relatively small base of support. To avoid losing balance, therefore, postural components must be controlled effectively in concert, when performing a purposeful movement. One of the strategies applied by the central nervous system to maintain balance and upright posture is an APA, which occurs during voluntary step initiation. The aim of this study was to compare the influence of an auditory stimulus (AS) on anticipatory postural adjustments in multiple scle¬rosis patients during a choice step reaction task.
Methods: The present study was a semi-experimental study. For the purpose of the study, 14 male people (mean age: 32.4±2.32 years) with MS from the members of the Tehran Multiple Sclerosis Association, were selected using purposeful and available sampling method. Each of the subjects performed a block of 20 trials of the choice reaction time (CRT) task on the force plate. The electromyography signals of the lower limb muscles recorded using an electromyography device during the assignment. Participants stepped forward in response to a visual imperative stimulus of an arrow (with the left or right foot in accordance the arrow direction) .The AS was presented randomly and simultaneously with the visual stimulus. The distribution of each direction in the presence or absence of audio stimuli counterbalanced (for each five attempts). Electromyography (EMG) activity of muscles was recorded from four right and left lower extremity muscles: medial gastrocnemius (GASM), tibialis anterior (TA). The RT was determined as the time at which the vertical force under either foot exceeded a threshold of 5% body weight from the baseline set as half body weight. Foot–lift time was detected as the time at which the vertical force under either foot became zero. Integrals of anticipatory and compensatory EMG activity were derived using average trials for each subject. Integrals of the EMG activities (IntEMGi) were calculated for four different epochs, each of 150 ms duration in relation to T0. The time windows for the four epochs were: 1) from −250 ms to −100 ms (anticipatory adjustments, APA1); 2) −100 ms to +50 ms (anticipatory adjustments, APA2); 3) +50 ms to 200 ms (compensatory reactions, CPA1); and 4), +200 ms to 350 ms (late compensatory reactions, CPA2). The reaction time was calculated using vertical ground reaction forces (vGRF).
Results: The results of the multidisciplinary t-test showed that the response time was faster in the presence of auditory stimuli in multiple sclerosis patients (p = 0.024). Also, the rate of predictive status adjustments in the presence of auditory stimuli was higher than in the absence of this stimulus (p <0.001).
Conclusion: Findings from this study provide a background for the development of perturbation–based training programs aimed at balance improvement and fall prevention by restoring mechanisms underlying balance impairments.
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Type of Study: Original Research Article | Subject: Rehabilitation
Received: 2018/11/19 | Accepted: 2018/12/8

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