Fig. 3

Weight-bearing asymmetry and prosthetic knee torque. (A) Index of Asymmetry (IOA) of the vertical GRF during sit-down with passive (gray) and powered (black) prostheses for all subjects from 0 to 100% of sit-down completion. Negative IOA indicates more weight on the prosthesis; positive IOA indicates more weight on the intact leg. Lines indicate across-subject means and shading indicates standard error (N=10 subjects). (B) Average IOA calculated between 0 and 100% of sit-down completion. Bar heights indicate the across-subject mean IOA (the across-subject average of the single-subject IOA means), and error bars indicate standard error (N=10 subjects). A paired t-test compared the across-subject means for passive and powered and found a significant difference (p = 0.0012). Colored dots overlaid on the bar plots indicate the single-subject IOA average (3 trials per subject) for each subject. The legend on the right shows which colored dot corresponds with each subject. (C) Prosthesis knee torque calculated using inverse dynamics. Shown during sit-down with passive (gray) and powered (black) prostheses for subjects who did not use hands, from 0 to 120% of sit-down completion. Knee extension torque is negative. Lines indicate across-subject means and shading indicates standard error (N=7 subjects). (D) Relation between prosthesis knee position and prosthesis knee torque during sit-down with passive (gray) and powered (black) prostheses for subjects who did not use hands, from 0 to 100% of sit-down completion. Lines indicate across-subject means and shading indicates standard error (N=7 subjects). Circle indicates start of the movement (standing), square indicates the end of the movement (sitting)