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Intra-rater Reliability of the ElectromyographicSignals of the Scapular Rotators Using the MVIC and RVICNormalizations

肩胛旋轉肌電活動以最大收縮及參考等長收縮方法標準化之信度研究

摘要


Background and Purpose: The electrmyographic (EMG) activity was often normalized by the maximum voluntary isometric contraction (MVIC) or a standardized reference voluntary isometric contraction (RVIC) task. The purpose of this study was to establish the intrarater reliability of the scapular muscle EMG activity during the MVIC and RVIC tasks, and to assess the correlation between these two normalization tasks for scapular rotators. Methods: Twenty healthy subjects without shoulder pain were recruited. Surface EMG signals were collected from the serratus anterior, upper trapezius and lower trapezius of the dominant arm during two sessions of MVIC and RVIC tasks. The subject performed the MVIC tests by exerting maximum contraction against a fixed resistance in 125∘ scaption (30∘horizontal shoulder abduction from the frontal plane) for the serratus anterior, 90∘scaption for the upper trapezius, and overhead arm elevation in the line of the muscle fibers for the lower trapezius. EMG activities during the RVIC task were recorded while the subject holding a 2-kg weight in 125∘arm scaption. Each contraction lasted 5 seconds for 3 times, with a 20-second rest period. The EMG signals were filtered (10-500 Hz) and root-mean-squared (RMS) with a window of 50 msec, and then averaged for the 5 seconds contraction. The two largest of the three contractions were selected and averaged for the final analysis. The reliability of the EMG activity was analyzed by the two-way mixed-effects model intraclass correlation coefficient (ICC(subscript 3.2)). The correlation between the EMG activities during MVIC and RVIC was calculated by Pearson's product moment correlation coefficient. Results: The reliability of EMG activity of the scapular muscles during the RVIC task (ICC>0.95) was higher than that during the MVIC tasks (ICC>0.91). In addition, the EMG activities of the scapular rotators during the RVIC task correlated significantly with those during the MVIC tasks (p<0.01). Conclusion: The scapular muscle EMG activity during the RVIC task proved to be a stable and valid value for the normalization purpose. The submaximum exertion during the RVIC causes less fatigue and pain problems when testing symptom subjects and the method was a good alternative method for the EMG normalization.

並列摘要


Background and Purpose: The electrmyographic (EMG) activity was often normalized by the maximum voluntary isometric contraction (MVIC) or a standardized reference voluntary isometric contraction (RVIC) task. The purpose of this study was to establish the intrarater reliability of the scapular muscle EMG activity during the MVIC and RVIC tasks, and to assess the correlation between these two normalization tasks for scapular rotators. Methods: Twenty healthy subjects without shoulder pain were recruited. Surface EMG signals were collected from the serratus anterior, upper trapezius and lower trapezius of the dominant arm during two sessions of MVIC and RVIC tasks. The subject performed the MVIC tests by exerting maximum contraction against a fixed resistance in 125∘ scaption (30∘horizontal shoulder abduction from the frontal plane) for the serratus anterior, 90∘scaption for the upper trapezius, and overhead arm elevation in the line of the muscle fibers for the lower trapezius. EMG activities during the RVIC task were recorded while the subject holding a 2-kg weight in 125∘arm scaption. Each contraction lasted 5 seconds for 3 times, with a 20-second rest period. The EMG signals were filtered (10-500 Hz) and root-mean-squared (RMS) with a window of 50 msec, and then averaged for the 5 seconds contraction. The two largest of the three contractions were selected and averaged for the final analysis. The reliability of the EMG activity was analyzed by the two-way mixed-effects model intraclass correlation coefficient (ICC(subscript 3.2)). The correlation between the EMG activities during MVIC and RVIC was calculated by Pearson's product moment correlation coefficient. Results: The reliability of EMG activity of the scapular muscles during the RVIC task (ICC>0.95) was higher than that during the MVIC tasks (ICC>0.91). In addition, the EMG activities of the scapular rotators during the RVIC task correlated significantly with those during the MVIC tasks (p<0.01). Conclusion: The scapular muscle EMG activity during the RVIC task proved to be a stable and valid value for the normalization purpose. The submaximum exertion during the RVIC causes less fatigue and pain problems when testing symptom subjects and the method was a good alternative method for the EMG normalization.

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