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. 2014 Dec;61(12):2891-8.
doi: 10.1109/TBME.2014.2333034. Epub 2014 Jun 25.

Examination of hand muscle activation and motor unit indices derived from surface EMG in chronic stroke

Xiaoyan Li, Jie Liu, Sheng Li, Ying-Chih Wang, Ping Zhou

Examination of hand muscle activation and motor unit indices derived from surface EMG in chronic stroke

Xiaoyan Li et al. IEEE Trans Biomed Eng. 2014 Dec.

Abstract

In this study, we used muscle and motor unit indices, derived from convenient surface electromyography (EMG) measurements, for examination of paretic muscle changes post stroke. For 12 stroke subjects, compound muscle action potential and voluntary surface EMG signals were recorded from paretic and contralateral first dorsal interosseous, abductor pollicis brevis, and abductor digiti minimi muscles. Muscle activation index (AI), motor unit number index (MUNIX), and motor unit size index (MUSIX) were then calculated for each muscle. There was a significant AI reduction for all the three muscles in paretic side compared with contralateral side, providing an evidence of muscle activation deficiency after stroke. The hand MUNIX (defined by summing the values from the three muscles) was significantly reduced in paretic side compared with contralateral side, whereas the hand MUSIX was not significantly different. Furthermore, diverse changes in MUNIX and MUSIX were observed from the three muscles. A major feature of the present examinations is the primary reliance on surface EMG, which offers practical benefits because it is noninvasive, induces minimal discomfort and can be performed quickly.

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Figures

Fig. 1
Fig. 1
Computation of MUNIX in (a) FDI, (b) APB, and (c) ADM muscles in both the paretic and contralateral sides of a stroke subject (Subject 9). Paretic: solid lines with stars; contralateral: dotted lines with squares. MUNIX is defined as the ICMUC value (Y-axis) when the surface EMG area (X-axis) equals 20 mV ms.
Fig. 2
Fig. 2
Comparison of (a) hand CMAP amplitude; (b) hand MUNIX; and (c) hand AI values between paretic and contralateral sides of 12 stroke subjects. The bars represent standard errors. The asterisk (*) indicates significant difference between the two groups. For detailed comparison of specific muscles please refer to the text.
Fig. 3
Fig. 3
Correlations between the hand CMAP amplitude and MUNIX values for both paretic and contralateral sides of stroke subjects.
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