Surface electromyography assessment of the biceps brachii muscle between the endplate region and distal tendon insertion: Comparison in terms of gender, dominant arm and contraction

[Purpose] In some earlier studies of electromyography (EMG) of the upper arm biceps brachii (BB), researchers preferred to place the electrodes on the middle of the biceps muscle to analyze its function. This study investigated the BB muscle activity between the region of the endplate and distal tendon insertion (electrode placed on lower part of the BB muscle belly). [Subjects and Methods] Six right-arm dominant Asian subjects (n=6, 3 males and 3 females), age range 20–30 years, who were free from any musculoskeletal disorder in BB, participated in this study. EMG signals were recorded from 12 BB muscles (6 subjects × 2 arms) during two types of muscle contraction (concentric and eccentric). Mean ± SD was calculated and analysis of variance (ANOVA) was performed. [Results] The results indicate that, the dominant right arm (R) of both males (M) and females (F) showed significantly higher activity than non-dominant left arm (L). In addition, there were interactions between M(L) and M(R), F(L) and F(R), M(L) and F(L), M(R) and F(R), and both male BB and both female BB; but, no interactions were found between M(L) and F(R), and M(R) and F(L). We also discovered that eccentric contraction generates higher EMG signals than the concentric contraction of that muscle region. [Conclusion] These findings suggest that EMG data are random on the BB muscle area we investigated during arm movement. These results should be considered in biceps tendonitis rehabilitation, muscle coordination and other physiological measurements of the upper limb muscles.