Figure 1 : Co-contraction index (CCI).

The black area indicates the right internal oblique muscle (right IE), and the white area indicates the left internal oblique muscle (left IE). The gray area indicates overlapping of the two lines, indicating simultaneous contraction. CCI was calculated as follows; CCI = 2 gray/(black+white + 2gray).

Okazawa et al.Physical Therapy and Rehabilitation  2019 6:13DOI : 10.7243/2055-2386-6-13