Electromyographic Responses during Elbow Movement at Two Angles with Voluntary Contraction: Influences of Muscle Activity on Upper Arm Biceps Brachii

Abstract

Analysis of Electromyography (EMG) signals generated by individuals is part of human musculoskeletal system research and signals are always influenced by the electrode placement in the muscle. This characteristic is also obvious at Biceps Brachii (BB) muscles during the movement of elbow at different angles. The purpose of this study was to monitor and determine the BB muscle function in 3 conditions: (i) electrodes were placed at 3 locations on the BB, (ii) elbow was fixed at the two angles (90° and 150°) and (iii) isometric contractions were performed to record EMG data. EMG data were obtained from six healthy subjects (n=6, mean±SD age=24.4±3.1 years, body mass=68±6.3 kg, height=164±4.1 cm, BMI=21.2±2.3, right arm dominated). A Bluetooth-enabled laptop, wireless EMG sensors, digital dynamometer and angle meter were used for data recording. EMG data were calculated and analyzed by average value, standard deviation, Root Mean Square (RMS) and highest peak of the signal during maximum voluntary contraction. All the dependent variables were calculated using repeated measures Analysis of Variance (ANOVA). The results from the research showed that (i) according to the calculation of average RMS and the maximum peaks of EMG signals, there was a significant difference between 2 angles (p=0.047, i.e., p＜0.05), but no interaction at the same angles when overall average EMG and standard deviation value are considered and (ii) majority of the outcomes showed that EMG activity is higher in the order of middle, upper and lower BB muscle. It is therefore important that electrical signals generated upon different electrode placements and angles on the BB muscle are used for biceps rehabilitation and other physiological measurements on upper arm.