Figure 8

Kinematic analysis. (a, b) compare the normalized biological hip torques, hip joints’ angles, and normalized assistive torques for the subjects with the highest and lowest metabolic rate reductions. The start of the gait cycle is at the heel-strike instant of the right leg, and the torque profiles in (a) and (b) are for the right leg. The swing phase is shown with a dashed line over the horizontal axes. Gray areas define the difference between the zero points of the biological hip torque and assistive torque. As it is clear, gray areas are much narrower for the subject with the highest metabolic rate reduction. (c–e) Compare three different defined kinematic indexes for estimating the metabolic rate reduction. In figures (c–e), each color indicates one subject. As can be seen, P value and goodness of fit are improved from RM, SM, and RS \(=\) RM \(\times\) SM, respectively. In (c), the linear regression (pink line) cannot properly estimate the metabolic rate such that there is an outlier (pink star) in this figure; by excluding the outliers based on the Jack-knife criterion (significance level \(=0.05\)), the goodness of fit of the linear regression (gray line) is improved. However, in (d, e), the outlier approaches to the linear regression and the goodness of fit improves further. Accordingly, the best index for having a good linear relation between metabolic rate reduction and kinematic parameters is RS.