Fig 1.
Experimental paradigm, setup and calculated gait parameters.
(A): Experimental paradigm of split-belt treadmill adaptation under five different split-belt ratio conditions. (B): Experimental setup. Three orthogonal ground reaction forces (GRF) were recorded bilaterally. (C-E): Gait parameters calculated in the present study. (C): Schematic representation of the gait cycle and the timing of heel contact (HC), toe off (TO), and stance time. Horizontal bars represent the stance time (HC to TO) of the slow (white bars) and fast legs (black bars). (D): Waveform of the anteroposterior GRF. The peak value of the anterior braking force in each gait cycle was calculated. (E): Foot placements and their center of pressures (COP) at the timing of HC on the fast leg. Step length was defined as the length between the right and left COPs at the time of HC.
Fig 2.
Time series changes in the symmetry indices of gait parameters (A: stance time, B: step length, C: anterior force). All data were normalized to those under the baseline condition. Left: Time series changes of the mean value of each 5-s bin. Right: Comparisons of each parameter at different time periods (baseline, first adaptation, last adaptation, first washout, and last washout). In the right panels, open circles denote significant differences against to the baseline period. Error bars indicate means ± SE. Significant differences were defined as p < 0.05.
Fig 3.
Relevance of the speed ratio (x-axis) to the symmetry index of stance time (A), step length (B), and anterior force (C) at initial adaptation and initial washout (y-axis). Each plot indicates individual data in each speed ratio. Regression lines and the correlation coefficients and their significance are presented.
Fig 4.
Relationship of the symmetry indices between the extent of adaptation and the initial aftereffect of predictive adapting parameters.
(A, C): Relationship of the symmetry indices between the extent of adaptation (x-axis) and the initial aftereffect (y-axis) for step length and anterior force, respectively. Each plot indicates individual data in each speed ratio. Regression lines and the correlation coefficients and their significance are denoted. (B, D): The open ellipses represent the 95% confidence ellipse for step length and anterior force in each five speed ratio conditions. Each plot indicates individual data. “+” markers indicates the centers of the ellipses. (E): Dendrogram of the hierarchical clustering analysis (Ward’s method, Euclidean distance) for the data sets of adaptive indices among the five speed ratios.
Table 1.
Characteristic parameters of the 95% confidence ellipses represented in Fig 4E.