Figure 1.
Ankle moment vs. relative angle curve for a representative subject walking at 1.75 m/s.
Letters a-f on the graph correspond to the poses schematically shown during a typical walking cycle (top, schematic timing is adapted from [69]). Quasi-stiffness is calculated based on the slope of the best-line fit to the moment-angle curve of b-c for the dorsi-flexion (), c-d for the dual-flexion (
), and d-e for the plantar-flexion (
) phases of the progression period (b-e). The area enclosed by the graph represents the propulsion work of the ankle (
). The joint excursion in each phase is the difference between the ankle relative angle at the onset and end of that phase (i.e. ,
and
Table 1.
Details on Subjects and Experimental Trials used for Regression Fits.
Table 2.
General-Form Models to Predict the Quasi-Stiffness and Work of the Ankle Joint for Level Ground Walking.
Figure 2.
Ankle quasi-stiffnesses (N.m/rad) in dorsi-flexion (top-left), dual-flexion (top-right), and plantar-flexion (bottom-left) phases, and propulsive work (J) in stance (bottom-tight) plotted against gait speed for subject 10 as an example.
The circles indicate the experimental value and the diamonds are the predictions of the general-form models of Table 2.
Figure 3.
Ankle quasi-stiffnesses (N.m/rad) in dorsi-flexion (top-left), dual-flexion (top-right), and plantar-flexion (bottom-left) phases, and propulsive work (J) in stance (bottom-tight) plotted for different subjects walking at a speed closest to the preferred gait speed.
The experimental values are shown by circles, the predictions of the general-form models by diamonds, and the stature-based models with squares. To avoid suppressing the rest of the data, the arrows are included on the top-right graph to indicate the values that are dramatically higher than the rest of the data.
Table 3.
Stature-Based Models to Predict the Quasi-Stiffness and Work of the Ankle Joint for Walking at the Optimal Gait Speed on Level Ground.
Table 4.
Average Error Values for Different Models.