Fig. 2.
a, Positional shifts and variational torques at the shoulder and elbow joints caused by perturbations in opposite directions (thick andthin lines for each perturbation) during a force regulation task (subject B, 10 N, x-direction). Fromtop to bottom, δθ, δτext,Dδq˙ +Rδq (solid line, observed;dashed line, reconstructed), and bothDδq˙ (dotted lines) and Rδq(dash-dot lines) at the shoulder (left graphs) and elbow (right graphs) are shown. b, The estimated distribution functions of viscosity and stiffness parameters obtained by random sampling (100 times) from experimental data (see Materials and Methods). The number attached in each graph is the mean value of the estimates for each parameter.