Saskia Baltrusch

102 Chapter 4 Muscle activity The muscle activity of the trunk muscles over a stride is shown in Figure 9. The muscle activity of the back muscles did not show significant differences between the exoskeleton conditions at either of the walking speeds. With regard to the abdominal muscle activity, a significant increase in muscle activity of the m. rectus abdominus was found when walking with the exoskeleton at PWSX, at three different time instances during the gait cycle (p=0.036, 0.049 and 0.050). The muscle activity of m. external oblique significantly increased in the ipsilateral initial swing when walking with the exoskeleton at PWS (p=0.041), and in the ipsilateral mid stance when walking with the exoskeleton at PWSX (p=0.026). Muscle activity in the legs did not show any significant differences between conditions. Figure 9: Left: Averaged time series of muscle activity per stride for each condition, averaged over participants when walking with and without exoskeleton in the preferred walking speed without exo (PWS) and in the preferred walking speed with exo (PWSX) N=9; Right: One dimensional repeated measures ANOVA (SPM1D) of muscle activity of the control condition compared to the exoskeleton condition. The horizontal axis displays the normalized stride cycle. The vertical axis displays the one dimensional F-statistic. A significant effect is present at instances where the black line is above the dotted horizontal red line.