Electromyography study of the portions of the abdominal rectus muscle.

This study objective was to verify the behavior of three portions of the abdominal rectus muscle through a quantitative analysis of the electromyographic signal in different types of abdominal exercises. Ten young male between 16 and 27 years old were studied and they had no previous history of muscle and joint illness. They were well-trained and did seven abdominal exercises chosen considering the types of contraction (isotonic and isometric) as well as the muscle fixation points. The electric activity of the superior, medium (above umbilicus) and inferior (below umbilicus) portions at the left side of the abdominal rectus muscle was taken using Beckman type surface mini-electrodes. The registers were collected from computerized 8-channel Nicholet electromyography equipment, model Viking II. The signals were quantified using the MVA (Maximum Volunteer Activity) software, being considered for analysis the values of RMS (Root Mean Square). The obtained data were submitted to a parametric analysis using the variance analysis (F test) and also the Tukey test, besides a descriptive graphic analysis starting from the average RMS values of each muscle portion. This study results suggest that for the majority of the subjects, the functional activities of the abdominal rectus muscle are performed with electric activity differences among their portions, showing a tendency of producing more electric activity in the superior portion than in the medium and inferior portions. The experiment also demonstrated an absence of a common behavior pattern in the three portions of the ten tested subjects.