Electromyography analysis of the rectus abdominis and external oblique muscles of children 8 to 10 years old.

The objective of this work was to study through in the electromyography the upper and lower umbilical rectus abdominis and the anterior and posterior parts of the external oblique muscles of children 8 to 10 years old. The children studied practice artistic and rhythmical gymnastic sports at the training and learning level and the study was made during abdominal exercise in the dorsal decubitus position on the ground and on a board. The children were divided into 2 groups: Group I - ten already trained children; Group II - nineteen learners. The participants in Group I practiced an average of 5 times a week and those in Group II practiced 2 times a week. The exercises analyzed were: on the ground, lifting the legs 30, 20 and 10 cm high with the knees flexed 90 degrees; flexing the trunk while maintaining the legs elevated and the knees flexed; flexing the trunk with homo and heterolateral rotation of the trunk while maintaining the legs elevated and the knees flexed. On the board, flexing the trunk with the knees flexed 90 degrees on top of the board inclined 30, 20 and 10 cm; flexing the trunk with rotation of the trunk homo and heterolateral with the knees flexed on the board inclined 30, 20 and 10 cm. The results showed that the superior umbilical part of the rectus abdominis muscle presented more intense action potential than the inferior-umbilical part; the more intense action potential occurred at the flexing of the trunk and at the flexing of the trunk with homo and heterolateral rotation. The anterior part of the external oblique muscle presented more intense action potential than the posterior part; the more intense action potential occurred at the flexing of the trunk and at the flexing of the trunk with heterolateral rotation. In both of the muscles the more intense action potential occurred between 45 and 60 degrees of flexing the trunk; the children in Group I presented more intense action potential than those in Group II; the exercise of lifting the flexed legs did not prove efficient for strengthening the analyzed abdominal muscle structure.