Figure 1. Example of reflex facilitation with 120 deg s⁻¹ repeated triangular wave perturbations performed in two subjects.

A, in the first subject (subject 8), an initial depression and gradual increase in joint torque was observed, with soleus (SOL) activity modulated with the torque responses. In contrast, MG was active during both dorsiflexion (DF) and plantarflexion (PF) perturbations, and did not appear to be related to joint torque. B, in the second subject (subject 2), PF torque demonstrated slight increases with repeated stretch, while SOL activity gradually increased. In contrast, MG responses were reduced during the repeated stretch. Changes in MG activity out of proportion with alterations in joint torque may be indicative of the flexed knee posture of subjects during testing.