Evaluation of muscle contraction by electromyography and sonography: For early diagnosis and prevention of sarcopenia

Abstract

Diagnostic methods leading to the prevention of sarcopenia are required. We evaluated quadriceps femoris muscle contraction using electromyograms (EMGs) and ultrasound (US) images. Surface EMGs were recorded in the rectus femoris muscle, vastus lateralis and vastus medialis during knee extension with a load. We obtained three muscular discharge ratios, and they were evaluated in terms of the amount of muscular discharge in search of the repand area by integration. From the US image, we determined the circumference and cross-sectional area on the transverse image and measured the pennation angle on the sagittal image. Under isometric contraction conditions, the amount of muscular discharge increased with the strength of contraction from weak to strong. In the rectus femoris muscle, there was a significant positive correlation between the imposed weight and the muscular discharge. Since the circumference was more stable than the cross-sectional area, it was selected for evaluation. The pennation angle was larger during traction than during resting. The circumference and pennation angle tended to increase owing to voluntary contraction. However, the values did not change when the weight exceeded a certain value. We found the possibility of muscle weakness evaluation by functional and morphological analysis using EMGs and US images.