Selective Activation of the External Obliques during Twisting

This study investigated selective activation of different regions of the external obliques. Six subjects performed sub-maximal isometric axial twisting exertions (20%, 40%, 60% of MVC) while assuming six different postures defined by three levels of axial rotation (-20°, 0°, 20°) and two levels of sagittal flexion (0° and 20°). As the subjects performed these isometric exertions, the integrated EMG activity was sampled at five different locations on both the right and the left external oblique muscles. The results showed significant differences in the activation of different regions of each of the external obliques. The implications of selective activation of these muscles on spine biomechanics are discussed.