Fig 1.
Schematic of the eight muscles that were used in the current study.
Fig 2.
Metabolic rate of soleus, calculated with the metabolic energy models for different conditions.
Metabolic rate as calculated by the metabolic energy expenditure models that are based on individual muscles of the soleus muscle at four activation levels, for an isometric condition, and a shortening and lengthening velocity of one optimal fiber length per second.
Fig 3.
Kinetics and kinematics at the normal speed.
Average ground reaction forces, joint angles, joint moments, and muscle forces for all trials at the normal speed (1.3 m/s). The shaded area denotes one standard deviation. The dashed line shows EMG data of level walking for comparison [34]. The graphs use Winter’s sign convention, where flexion angles and extension moments are positive for hip and knee. Dorsiflexion angle and plantarflexion moment are positive for the ankle.
Fig 4.
Kinetics and kinematics for the slow speed.
Average ground reaction forces, joint angles, joint moments, and muscle forces for all trials at the slow speed (0.8 m/s). The shaded area denotes on standard deviation. The graphs use Winter’s sign convention, where flexion angles and extension moments are positive for hip and knee. Dorsiflexion angle and plantarflexion moment are positive for the ankle.
Fig 5.
Calculated and measured metabolic cost for all trials and models.
Calculated metabolic cost for all speeds and inclines, for each model, separately for the joints. The number above the bar indicates the walking speed. Biarticular muscles were added by ratio of the moment arm, similar to [26].
Table 1.
Root mean square (RMS) error between the calculated and measured metabolic cost in J/kg/m for all models and all trials.
Fig 6.
Correlation graphs for all models.
Correlation graphs between calculated and measured metabolic costs for each model. The lines show the regression model that was fitted by the repeated measured correlation.
Table 2.
Results of repeated measures correlation.
Repeated measures correlation coefficient rrm [37] with 95% confidence interval (CI) and slope of the repeated measures model.