Fig. 3

Frequency response functions magnitude, phase, and coherence for a typical stroke patient. Each colored line highlights a different level of arm weight support. The black dashed lines represent the best parametric fit for each condition. For this stroke patient, a lower elbow admittance magnitude (higher elbow stiffness) was found with reduced levels of arm weight support during the ‘do not intervene’ (DNI) task conditions, indicative of the presence of a shoulder-elbow synergy. Moreover, elbow admittance is lower during the active resist task than the DNI task. The high (> 0.8) coherence demonstrates a highly linear relationship between elbow torque and angle, and a low noise contribution