The muscles of the abdominal wall: a new functional approach with anatomoclinical deductions.

The basic functional anatomy of muscle can be investigated by histochemical analysis of the muscle fibers and kinesiologic electromyography. The results of these techniques lead to anatomoclinical deductions based on the structure of muscle. Histochemical analysis of the striated fibers of a given muscle shows the existence of three functionally different populations of fibers. The relative abundance of each category of muscle fibers (expressed as a percentage) demonstrates the basic function of the muscle. The investigation of muscle function by kinesiologic electromyography shows that there are three categories of motor activity in the course of movement. These different types of motor activity are dependent upon the muscle fibers which display different physiological features, especially with respect to their contraction time. These two investigative techniques, the overall results of which are concordant, were applied to the study of the function of the muscles of the abdominal wall and led to the following anatomo-clinical deduction: tonico-postural motor activity is predominant in the rectus abdominis and flat abdominal muscles. Kinesiologic electromyography also allowed to demonstrate the functional development of these muscles according to the age, sex, corpulence and physical activity of the subjects studied.