Is the EMGs Amplitude Distribution Spatially Localized in the Pectoralis Major Muscle During the Inclined Bench Press?

This study implements the novel high-density surface electromyography (EMG) to investigate the distribution of pectoralis major (PM) muscle activity during the inclined bench press exercise. Six healthy male individuals participated in this study. Subjects performed one set of eight repetitions of the inclined (45°) bench press exercise. They used 70% of their one-repetition maximum load. EMGs activity was recorded with an array of sixteen electrodes perpendicularly placed above PM muscle fibers between innervation zone and sternocostal tendon region. For each contraction, the root mean square value (RMS) was computed. Additionally, active channels were defined as EMGs with RMS amplitude greater than 70% of the maximum amplitude for each contraction, respectively. Considering the active channels, the barycenter coordinate was calculated indicating the mean position of the RMS distribution along cranio-caudal axis of PM muscle. For all the volunteers, we identified the barycenter coordinate located near to the clavicular portion, indicating that there is a localized activation on PM during 8 repetitions of the inclined bench press.