The within-day reliability of scapular and shoulder emg measurements in asymptomatic individuals during shoulder abduction

Abstract

The purpose of this study was to assess the within-day reliability of scapular and shoulder surface electromyography (sEMG) measurements during shoulder abduction. Twenty asymptomatic individuals performed 10 repetitions of shoulder abduction, which was then retested 10 minutes later. sEMG was used to record the activity of upper and lower trapezius; anterior, middle and posterior deltoids; supraspinatus; infraspinatus; and serratus anterior muscles. Muscle activation was expressed as a percentage of maximum voluntary isometric contraction (MVIC). The intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were used to assess within-day reliability for concentric and eccentric phases of shoulder abduction. For the concentric phase, ICC values ranged from 0.87 to 0.98 and SEM values from 8.6% to 18.9% MVIC. For the eccentric phase, ICC values ranged from 0.65 to 0.97, and SEM values from 9.8% to 24.4% MVIC. In asymptomatic individuals, EMG measurements of the scapular and shoulder muscles during the concentric phase of shoulder abduction had excellent reliability, and for the eccentric phase, had good to excellent reliability depending on the analysed muscle. These findings provide valuable information on reliability of sEMG for assessing muscle activity of scapular and shoulder muscles.